UNIVERSITY OF GHANA
SCHOOL OF ALLIED HEALTH SCIENCES
COLLEGE OF HEALTH SCIENCES
DEPARTMENT OF AUDIOLOGY
PREVALENCE OF HEARING IMPAIRMENT AT THE KORLE-BU
TEACHING HOSPITAL
ELSIE AKOSUA NYARKO
(10373993)
A DISSERTATION SUBMITTED TO THE UNIVERSITY OF GHANA,
LEGON, IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR
THE AWARD OF MSc AUDIOLOGY.
JULY, 2013.
University of Ghana http://ugspace.ug.edu.gh
i
DECLARATION
I, ELSIE AKOSUA NYARKO hereb y decla re th at thi s diss ertati on which is being subm it ted in
partial fulfil lm ent of the requirements fo r the de gr ee of MSc. in Audiolo g y is the result of m y
own independent res ear c h project or investi gati on and that, ex cept where otherwise other sour ces
are ackn owled ged with ex pli cit references and are included in the refer e nce list, thi s work has
not previous l y be en acc epted in subst ance fo r an y de gree and neit he r is it being con curr entl y
subm it ted in candidature for an y de gree.
Signed ……………………………………………………… Date ………………...
ELSIE AKOSUA NYARKO (10373993)
Signed ……………………………………………………… Date ………………...
PROF GEOFFREY AMEDOFU
(Principal Supervisor)
Signed ……………………………………………………… Date ………………...
PROF. JOHN E. RIBERA
(Secondar y Supe rvisor)
University of Ghana http://ugspace.ug.edu.gh
ii
DEDICATION
I dedicate this work to m y mum , Chris ti ana Serw a a Boat en g and m y husba nd Brian Otuo -
Ac heampon g.
University of Ghana http://ugspace.ug.edu.gh
iii
ACKNOWLEDGEMENTS
I will like to ex pr ess my profound gr ati tude to the giver of life, J ehova h God for seein g me
through thi s pro gr am suc cessfull y. I am also most grate ful to m y academi c supervisor s , Pro f. G.
K. Amedofu, Prof J ohn E. Ribera and Dr. Anim - Sampong for their co rre cti ons, suggesti ons and
guidan ce. The y have con tribut ed immensel y in making thi s work a succ ess .
M y nex t thanks go to th e enti re staf f of the Hea r ing Ass essm ent Centre (KBTH ) esp eciall y Mrs
J emi ma Fynn, Mrs J osephine Decke r- An ye e, Mr Geor ge Te ye, Mrs Flor e nce Asiedua Mens ah ,
Mrs Grac e Ocanse y and Mrs Rejoice Acqu ah.
The followin g people als o deserv e a lot of thanks from me; the y ar e Rona ld Nkansah Adj ekum ,
Graham Amponsah Ame ya w , Col li ns Sesi Akot e y and Jo yce Es enam Ano mah .
S pecial thanks to all m y friends espe ciall y Esthe r Kwa k ye waa, Seth and Racheal Kw ao, Mrs.
J uliana Owusu -Adu and all who were a pil lar of support to me during the two ye ars of my stud y.
Lastl y, I would li ke to thank m y sibl in gs, Emmanuel, Zadok and Agnes for their immense
support. Ma y J ehovah ri c hl y bless you all .
University of Ghana http://ugspace.ug.edu.gh
iv
TABLE OF CONTENTS
TITLE PAGE
DEC LARAT ION i
DED IC AT IO N ii
ACKNOW LED GEMEN T iii
TABLE OF CONTE NTS iv
LIST OF TA B LES viii
LIS T OF FIGUR ES ix
APP END IX x
AB STRAC T xi
CHAPTER ONE INTRODUCTION
1.1 BACKGR OUN D OF TH E STUDY 1
1.2 PROBLEM STATEME NT 3
1.3 S IGN IF IC ANC E OF TH E STUDY 5
1.4 AIM OF THE RESEARC H 6
1.5 RESEAR C H OBJ ECT IVES 6
1.6 RESEAR C H QUEST IO NS 7
1.7 PROFILE OF THE STU DY AREA 7
1.8 ORGAN IZAT ION OF WORK 7
University of Ghana http://ugspace.ug.edu.gh
v
CHAPTER TWO LITERATURE REVIEW
2.1 IN TRODUC T IO N 9
2.2 PREVA LENCE STUD IES 9
2.3 TYPES OF HEAR ING LOSS 1 0
2.3 .1 Conducti ve Hearin g Loss 1 0
2.3 .2 Sensorineural Hearin g Loss 1 1
2.3 .3 Mix ed Hearing Loss 1 3
2.4 DEGR EE OF HEAR ING LOSS 1 3
2.5 GENDER DIS TR IB UT ION OF HEAR ING LOS S 1 4
2.6 DIS TR IB UT ION OF HE AR IN G LOSS AMONG VAR IOUS AGES 16
2.6 .1 Age Related Hearin g Los s (Presb yc usis ) 1 6
2.6 .2 Hearin g Loss in Chi ldren 1 7
2.7 UNILATER A L AND BILATER A L HEAR ING LOSS 18
2.8 COMMON CAUS ES OF HEAR IN G LOSS 19
2.8 .1 Occupati onal Nois e Ex posure 19
2.8 .2 Otit is Media 21
2.8 .3 Impa cted Cerum en 22
2.9 C LIN IC A L PROCEDUR ES FOR DETER M IN ING HEAR ING LOSS 2 2
2.9 .1 Pati ent Histor y Intak e 22
2.9 .2 Pure Tone- Audiometr y 2 2
2.9 .3 Otoacoust ic Emiss ions 2 2
2.9 .4 Tympanomet r y 2 4
2.10 CONC LUS IO N 2 5
University of Ghana http://ugspace.ug.edu.gh
vi
CHAPTER THREE METHODOLOGY
3.1 IN TRODUC T IO N 2 6
3.2 STUDY DES IGN 2 6
3.3 STUDY S ITE 26
3.4 SAMP LING 27
3.5 SAMP LE S IZE 27
3.6 PROCEDUR E FOR DA TA CO LLECT ION 28
3.7 INC LUS IO N AN D EXC LUS IO N CR IT ER IA 28
3.4.1 In clusi on Crit eria 28
3.4.2 Ex clusi on Crit eria 28
3.8 RESEAR C H TOO LS 28
3.5.1 Audiogr ams 28
3.5.2 Tympano grams 3 1
3.5.3 Otoacoust ic Emiss ion Result s 3 2
3.9 DATA MANA GEMEN T P LAN 3 2
3.10 ANA LYS IS 3 3
3.11 ETH IC A L CONS IDER AT IONS 3 3
3.12 DIS S EM IN AT ION OF RESU LTS 3 3
CHAPTER FOUR RESULTS
4.1 IN TRODUC T IO N 3 4
4.2 DEMOGRAP H IC VAR IAB LES 34
University of Ghana http://ugspace.ug.edu.gh
vii
4.2.1 Gender Demographics 34
4.2.2 Age Demo gr aphics 34
4 .3 TYPES OF HEAR ING LOSS 3 6
4.4 AUD IOMETR IC CON F IG URAT IO N OF HEAR IN G LOSS 37
4.5 OTOACOUS T IC EM IS S ION AND TYMPAN O METRY ANA LYS IS 39
CHAPTER FIVE DISCUSSION
5.1 IN TRODUC T IO N 41
5.2 DEMOGRAP H IC PATT ERN OF HEAR IN G LO S S 41
5.2.1 Gender Dist ributi on of Hearin g Loss 41
5.2.2 Age Dist ributi on of Hea r ing Loss 42
5.3 TYPES OF HEAR ING IMPA IR MENT AMO NG THE STUDY POP U LA T ION 43
5.4 UNILATER A L VERS US BILATER A L HE AR ING LOSS 43
5.5 AUD IOMETR IC CON F IG URAT IO N OF HEAR IN G LOSS 44
5.6 OTOACOUS T IC EM IS S IONS 44
5.7 TYMPANOMETRY 44
CHAPTER SIX CONCLUSION AND RECOMMENDATIONS
6.1 IN TRODUC T IO N 46
6.2 CON LUS IO N 46
6.3 RECOMMENDAT IONS 47
University of Ghana http://ugspace.ug.edu.gh
viii
LIST OF TABLES
Table 3.1 Stud y variables
Table 4.1 Gender dif fer enc e and f r equenc y of att endan ce of pati ents
Table 4.2 Age diffe renc e and frequ enc y of att end anc e of pat ients
Table 4.3 Frequ enc y dist ributi on of hearin g loss for gender and var yin g age cate go rie s
Table 4.4 Prevalenc e of t ypes of hearing loss evaluated for both ears
Table 4.5 Audiometric confi gur ati on of evaluated hea ring lo ss for ri ght and left ears
Table 4.6 Evaluated OAE passes/re ferr als and t ypes of midd le ear disord ers
University of Ghana http://ugspace.ug.edu.gh
ix
LIST OF FIGURES
Figu re 2.1 Prevalenc e of hearin g los s b y age group and gende r
Figu re 3.1 Audiometric confi gur ati on of hearin g loss
Figu re 3.2 An audiogram of sensori neural he arin g loss
Figu re 3.3 An audiogram of conduc ti ve hearin g loss
Figu re 3.4 An audiogram of a mix ed hearin g loss
Figu re 4.1 Dist ributi on of t yp es of hearin g loss in bot h ears
Figu re 4.2 Degre e of ev aluated hear ing loss in left and ri ght ears
Figu re 4.3 Tympanomet r y in left an d right ears
University of Ghana http://ugspace.ug.edu.gh
x
APPENDIX
APP END IX I KBTH Audio gram Fo rm
APP END IX II Lett e r to the Hearin g Ass essm ent Centre of KBTH
APP END IX III Ethi cal Clearan ce Form
University of Ghana http://ugspace.ug.edu.gh
xi
ABSTRACT
BACKGROUND: Hear ing loss makes a large contribut ion to the global burden of disease,
which subst anti all y adv ersel y af fect social and economi c developm ent in comm unit ies and
countries. Due to thi s, WHO therefo re promotes surve ys and gathers data for measurin g the
burden of deafness and hearin g impairment. At KBTH, dat a on the prevalen ce of hearin g
impairment is lacking. There is therefo re the nee d for accur ate prev alenc e studi es to be carried
out in Ghana to enable healt h or ganiz ati ons and the medical pro fessi on to economi call y an al yz e
the burden of hearin g im pairme nt.
AIM: To determi ne the prevalen ce of hearin g im pairment at KBTH.
METHODS : A retrospe cti ve revie w of the reco rds of 715 pati ents who visi ted the Hearin g
Assessm ent Centre of KBTH durin g the periods of Januar y - Dec ember 2013 was co nducted .
RESULTS : Four hundred and sevent y four (66.3 %) had a significant hea ring loss . The highest
prevalen ce of hearin g l oss was reco rded fo r the age group 60 and ab ove. The over al l data
gath ered su ggested that, sensorineural he arin g loss was the most prevalent for both the left and
right ears, with pr evalen ce rates of 36.7 % and 40.5% in the ri ght and l ef t ears respecti vel y. In
addit ion, mil d hearing lo ss was the most prevalent .
KEYWORDS: He arin g loss , t ympanom etr y, prevalen ce, senso rineura l, conducti ve, mix ed
hearin g los s, Korle -Bu Teachin g Hospit al
University of Ghana http://ugspace.ug.edu.gh
xii
University of Ghana http://ugspace.ug.edu.gh
1
CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
The burden of hea ring impairment on both chil dren and adult s cannot be over emphasiz ed.
Hearin g loss in chil dren is a sil ent hidden hand icap: it is hidden becaus e chil dren, espe ciall y
infants and toddl ers cannot tell us that the y ar e not hearing well . It i s a handicap bec ause, if
undetected and untre ate d, hearin g loss in chil dren can lead to dela yed speech and lan gua ge
developm ent, social and economi c problems and acad emi c fail ure (Northe rn and Downs, 1991).
The negati ve impact of hearin g loss on older ad ult s is significant (La For ge et al., 1992). Adult
hearin g loss is often associated with an in cre ased risk of ps ychiatric and effe cti ve mood
disorders. A person with hea ring loss is likel y to ex perience feeli ngs of fr ustrati on, sadness and
isol ati on as his/ her int erpersonal and so cial life na rrows. This is bec ause he aring impaired adult s
(and chil dren) are often sociall y sti gm ati z ed. Hearing loss is associated with depressi on, social
isol ati on, poor self - estee m, and fun cti onal disabil it y pa rticularl y for tho se sufferin g from hearin g
impairment , who have not been evaluated or treat ed for he ari n g loss (Mulrow et al., 1990a). The
problem of hea ring loss is wide spread. In th e Unit ed States of America, it is the fourth most
comm on developm ental disorder and deafn ess is the most comm on sensor y disorde r. The
incidence of con genit al hearin g loss based on univ ersal neonatal scr eenin g programs is esti mated
to be 1.1 per 1,000 with a ran ge of 0.22 ±3.61 pe r 1,000 betwe en indi vidual states ( M ehra, Eav e y
and Keam y, 2009 ).
University of Ghana http://ugspace.ug.edu.gh
2
In Australi a, it is esti mated that on e in six per sons is hearin g impair e d . Prevalen ce rates for
hearin g loss are asso ciate d with incr easin g age, rising from less than 1% fo r people aged youn ger
than 15 years to 75% fo r people aged over 70 ye ars. Wit h an a gein g pop ulation, hearin g loss is
projected to incr ease to 1 in ever y 4 Austr ali ans by 2050. Nearl y 50 % of t he people with he arin g
loss are in th e workin g age (15 -64 yea rs) and ther e ar e an esti mated 158,8 76 unempl o ye d peopl e
in 2005 due to hearin g lo ss (Acc ess Economi cs Report, 2006).
In addit ion to its effects on indi vidual s , hearing impairment makes a lar ge contribut ion to the
global burden of diseas e, which subst anti all y adv e rsel y affe cts social and economi c developm ent
in comm unit ies and cou ntries . In developi n g co u ntries, chil dren with he a ring loss and deafn ess
rarel y receive an y schoo li ng. Adults with hea ring loss also have a much high er un empl o ym ent
rate. Amon g those who are empl o yed, a hi ghe r pe rcenta ge of people with hear in g loss are in the
lower levels of empl o yment compared with the gene ral wo rkfor ce. Accordin g to the World
Healt h Organiz ati on (W HO), i mproving ac ce ss to educati on and vocati onal reh abil it ati on
services, and raisi n g awa reness especi all y amon g empl o ye r s would dec reas e unempl o yment rates
among adult s with hea rin g loss (WHO, 2012). For ex ampl e, it has bee n esti mated that the cost of
comm unicati on disorders to the U.S . econom y ran ged betwe en US$176 bil li on and 212 bil li on in
1999, repres enti ng 2.5 -3 % of the gross nati onal product (Rub en, 2000). In Australi a, the real
financial cost of hea ring loss was $11.75 bil li on or 1.4% of Gross Dome sti c Product (GDP) in
2005. This figure rep rese nts an avera ge cost of $3,314 per person per annu m for each of the 3.55
mill ion Australi ans who have he a rin g loss or $578 for eve r y Australi a n (Ac c ess Economi cs
Report, 2006).
University of Ghana http://ugspace.ug.edu.gh
3
Various prev alenc e studi es have be en ca rried out in some develop ing cou ntries. Saunders et al
(2007) an al yz ed cli nical screenin g data in ru ral sc hools as well as data on pediatric h earin g loss
pati ents data seen at a clinic from a stud y condu cted on the pr evalen ce and eti olog y of hearin g
loss in rural Ni car a guan chil dren , and establi shed a hi gh preval ence of significant hea ring loss
ޓ d% RI aPRng tKe VFKRRO FKiOdUen. The cli n ic bas ed ev aluation reveal ed a population
with a pr edomi nantl y se vere -p rofound hea ring lo ss. A related stud y on th e pr evalen ce and risk
factors of hea ring loss among Sierra Leon ean chil dren was cond ucted by Seel y et al (1995 ).
Among the 2015 chil dre n evaluated, a tot al of 18 4 (9.1%) pr esented with mild or gr eater hea rin g
loss indi cati ng a hi gh prevalen ce. Anoth er scr ee ning pro gr am stud y con ducted in Gambi a b y
McPherson and Holbo ro w (1985) to det ermine t he incidenc e and causes of sever e to prof ound
hearin g loss showed that , a prim aril y preventi ve approach ma y prove to be the most rati onal way
of reducin g the in cidenc e .
:KiOe inteUYentiRnV VXFK aV KeaUing aidV and FRFKOeaU iPSOantV enKanFe a SeUVRn¶V aEiOit\ tR
comm unicate, WHO esti mates th at fewer than 1 in 40 people will ne ed a hearin g aid . Various
studi es have be en condu cted in Ghan a but the ex act prevalenc e of hea ring impairment at the
Korle- Bu Teachin g Hosp it al (KBTH ) is yet to be establi shed.
1.2 PROBLEM STATEMENT
Accordin g to WHO rep orts, o YeU RI tKe ZRUOd¶V SRSXOatiRn (360 mill ion ) people have
disabli ng hea rin g loss (328 mill ion adult s and 32 mill ion chil dren) (WHO, 2012). Disabli n g
hearin g loss ref ers to hearing loss gr eate r than 40dB in the bett er hearin g ear in adult s and a
hearin g loss great er th an 30dB in th e bett e r he arin g ea r in chil dren. Ov er 275 mill ion people ar e
esti mated to have moder ate to profound hea rin g loss in both ears. The figu re is about 4.2% of the
University of Ghana http://ugspace.ug.edu.gh
4
ZRUOd¶V SRSXOatiRn. $OVR PiOOiRn SeRSOe KaYe PiOd KeaUing ORVV and RI deaI and
hearin g-im pair ed people live in low and middle -income countries (WHO, 2012).
It is esti mated again tha t about 50% cases of hearin g loss can be pr ev ented through primar y
preventi on. Some simple strate gies for preventi on include:
im muni z ati on of chil dren against chil dhood diseases, includin g measl es , meningit is,
rubell a and mum ps.
im muni z ati on of adolesc ent girls and women of reproducti ve age against rubell a befo re
pre gnanc y;
s creenin g fo r and tr eati n g s yphil is and oth er inf ec ti ons in pregnant wom en.
im provement of anten ata l and perinatal care, in cludi ng promoti on of saf e chil dbirth.
avoidi ng the use of otot ox ic drugs, unless pr es cribed and mon it ored by a quali fied
ph ysician.
refe rrin g babi es with high risk facto rs (such as t hose with a fami l y hist o r y of deafness,
those born with low bi rth wei ght, birth asph yx ia, jaundice or m eningit is) fo r earl y
assessment of hearin g, pr ompt diagnosi s and appr opriate mana gement as required.
reducin g ex posure (bot h occupati onal and rec reati onal) to loud noises by creati n g
awar eness, using pe rsonal protecti ve devices, an d developi ng and implementi ng suit able
legisl ati on.
WHO therefor e promot e s surve ys and gathers data for measu ring the burden of dea fness and
hearin g impairment. A number of surve ys have been undertak en in variou s countries ex cludi ng
Ghana. Th e result s of th ese surv e ys were discus sed durin g a meeti n g of the ke y inv esti gators
held in the WHO headqu arters in Gen eva, Switz erland in 2003. Acco rding to the WHO surv e ys,
University of Ghana http://ugspace.ug.edu.gh
5
at least half of all hearin g impairment is pr eventa ble. A lar ge perc enta ge can be tre ated throu gh
earl y dia gnosi s and suita ble mana gement (W HO, 2012).
Based on ex trapol ati ons on *Kana¶V population , it is estimated that about 1,678,877 people are
hearin g impaired ( www. rightdi a gnosi s.com). Th is statis ti cs for esti mating the pr evalenc e or
incidence of hea ring im pairment in Ghana are typ ic all y based on ex trapolated result s from the
U. S ., U. K. , Canadian or Australi an preval enc e or incid ence statis ti cs . In particul ar, this
ex trapolation model is autom ated and does not assum e take int o account an y geneti c, cult ural,
environmental, social, an d racial or oth e r diff eren ces across the va rious co untries and regions fo r
which the ex trapolated hearin g impairment statis tics refer. Furthermor e, the model does not use
data sourc es or statis ti cs about an y countr y other than its population. As such, these
ex trapolations ma y be highl y inaccu rate (especi all y for dev elopi ng or thi r d -world countries). It
onl y gives a gener al ind icati on (or even a mean ingless indi c ati on) as to actual prev alenc e or
incidence of hea ring imp airment in the region.
There is ther efor e the ne ed fo r accu rate prevalen ce studi es to be c arri ed out in Ghana to enabl e
healt h or ganiz ati ons and audiol ogist s in particular to economi call y anal yz e the burden of hearin g
impairment.
1.3 SIGNIFICANCE OF THE STUDY
First l y , thi s resea rch wil l help deepen awa reness of prev alence of hearin g impairment at the
KBTH and all the othe r regions that are depen d ent on KBTH fo r hea r ing assessment. This
resea rch was design ed t o help identif y the gr av it y of the probl em. The data can be used to
quanti f y or ass ess the co st of hea ring impairment on so ciet y. This will hel p all stake holders and
University of Ghana http://ugspace.ug.edu.gh
6
decisi on makers in heal thcare to desi gn strate gi es and poli cies that will help to prevent the
negati ve ef fe cts of hea ring disorde rs .
Secondl y, a publ ic healt h approach to the problem of hearin g impairment can be developed us in g
the findings of thi s stud y to assi st healt h planners and professi onals plan ac ti vit ies . This research
enumerates the condit io ns that shoul d be targeted in order to solve the problems posed by
hearin g impairm ent and will also help healt h plan ners know the resour ces required for all ocati on
toward prev enti on , treat ment as well reh abil it ati on of indi viduals with hearing imp airment.
Finall y, th e res ear ch dat a can se rve as an infe renti al source of information from which the burd en
of hearin g impairment in other regions of the countr y can be reali z ed . Eco nomi c anal ysis studi es
can then be carried out t o determi ne the costs of the burden of hea rin g im pairment and the cost -
effe cti veness of dif fer ent int erventi on against it.
1.4 AIM OF THE RESEARCH
The aim of this rese arch was to determine the prevalence of hea rin g impairment at KBT H.
1.5 RESEARCH OBJECTIVES
The specific obj ecti ves for thi s stud y include d:
determi nati on of the number of pati ents refer red annuall y to KBT H Hea ri ng Assessm ent
Center
establi shing the prevalen ce of hearin g loss amon g the ref err ed pati ents
ascert aini ng the t yp e of hearin g impairment with the high est preval ence rat e
finding the con fi gurati on of hearin g loss with the highest pr evalen ce
University of Ghana http://ugspace.ug.edu.gh
7
determi nati on of gend er and age groups with the highest pr evalen ce rate s .
1.6 RESEARCH QUESTIONS
The rese ar ch questi ons posed for the stud y were as follows :
Which typ e of hearin g i mpairment is dom inant?
Which age group re cords the highest rate of hearin g impairment?
What is the dist ributi on of hearin g impairment among the sex es?
Which degr ee (t yp e and configu rati on) of hearin g loss is most prevalent?
1.7 PROFILE OF THE STUDY AREA
KBTH is the pr emi er he alt h care facil it y in Ghan a. It is the onl y te rtiar y hospi tal in the sout hern
part of Ghana and it is also a te achin g hospi tal affil iated to th e Coll e ge of Healt h Scien ces,
Universit y of Gh ana. The Hearin g Assessm ent Center of KBT H is a st ate of the art facil it y
establi shed in 2005 to provide audiol ogic al servic e s to the Greater Acc ra, Volta, Eastern, Central
and Western Re gion s. Addit ionall y, th e Center also provides servic e to all o ther pati ents refer red
from the othe r re gional h ospi tals. Pati ents from ot her West African countri es including To go and
Benin also ben efit from t he Hea ring Assessm ent Center.
1.8 ORGANIZATION OF WORK
This dissertation is divided int o six main chapters organiz ed as follows:
1. C hapter One discuss es the nature and back ground of the rese ar ch problem and identifies
the rese arch topi c, its obj ecti ves, jus ti ficati on, sco pe and limi tation
2. Chapter T wo cov ers rele vant lit erature related to prevalen ce of hearin g im pairment.
3. Chapter T hre e de als with methods and techniques used for data coll ecti on.
University of Ghana http://ugspace.ug.edu.gh
8
4. Chapter Fou r is devoted to the main result s and fin dings of the data coll e cte d.
5. Chapter Five deals with the discussi on of the main result s enumerat ed in Chapter Fou r.
6. Chapter Six deals with conclusi ons drawn fro m the stud y and make s appropriate
recomm endati ons to the Regional Healt h Dire ctor ate and the Mini str y of Healt h.
University of Ghana http://ugspace.ug.edu.gh
9
CHAPTER TWO
LITERATURE REVIEW
2.1 INTRODUCTION
This Chapter reviews relevant literature and cov ers areas such as prev al ence studi es, t yp es of
hearin g impairment, de gr ee of hearin g loss , dist ributi on of hearing l oss among males and
females . Dist ributi on of hearin g loss among vari ous ages, unil ateral and bil ateral hea ring loss ,
some comm on causes of hearin g impairment an d cli nical proc edures for de termi ning he arin g loss
are also review ed
2.2 PREVALENCE STUDIES
P revalenc e is the proport ion or per c enta ge of peo ple aff ected b y a condit ion at a point in time. It
is arrived at b y comp ar ing the number of peop le found to have the co ndit ion with the tot al
number of people studi ed, and is usuall y ex pressed as a fracti on or percent a ge . Prevalen ce
studi es can be viewed as a sli ce through the population at a point in time at which it is
determi ned who has the disease and who does not . In medic al and pu bli c healt h literature,
prevalen ce is often used as eit her point prevalen ce or period prev alenc e (Gordis, 2000). Point
prevalen ce is the propor ti on of a population that has the condit io n at a specific point in time.
Period preval ence on the other hand is the propo rtion of a population tha t has the condit ion at
some time during a give n perio d and includes pe ople who alread y have th e condit ion at the start
of the stud y period as well as thos e who acqu ire it during that pe riod .
University of Ghana http://ugspace.ug.edu.gh
1 0
P revalenc e studi es are however limi ted in scope as the y do not m easur e the du rati on of the
disease as well as new cases. Neverthel ess, the y are important for esti mating the burde n of
disease. In the curr ent s tud y, period pr evalen ce was us ed to me asure t he burden of hearin g
impairment at KBTH.
2.3 TYPES OF HEARING IMPAIRMENT
Hearin g impairment is a deviation or chan ge for t he worse in eit her audit or y structur e or audit or y
functi on, usuall y outsi de the ran ge of normal ( G elfand, 2009). Hea ring loss can be cate goriz ed
by whi ch pa rt of the audit or y s ystem is dam a ged. Ther e are thr ee t ypes of hearin g loss :
conducti ve, sensorineu ral and mix ed hearing loss .
2.3.1 Conductive Hearin g Loss
C onducti ve hearin g loss occurs when sou nd is not conducted efficientl y through the outer ear
canal to the eardrum and tin y bon e (ossicles) of the middle ear. Conducti ve hearin g loss usuall y
invol ves a reducti on in sound level or the abil it y to hear faint sounds. Thi s t ype of hearin g loss
can often be cor rect ed medicall y or sur gi call y. Some possi ble causes of conducti ve hearin g loss
are fluid in the middle ear from colds, ear infecti ons, all er gies, poor Eustachian functi on,
perfor ated eardrum, beni gn tum ors, impacted ear wax , infecti on in the ca nal, swim mers ear and
ab sence or malform ati on of the outer ear, ear canal or middl e ear.
Accordin g to the Am eri can Spee ch and Hearin g Association (AS HA), f luctuati ng conducti ve
hearin g loss nearl y alw a ys oc curs with all t ypes of oti ti s media. In fact it i s the most comm on
cause of hearin g loss in youn g chil dr en (AS HA , 2008 ). A retrospe cti ve chart revi ew of 234
infants refer red for ne wb orn hearin g scre enin g at the Audiolog y Departme nt of The Townsvi ll e
University of Ghana http://ugspace.ug.edu.gh
1 1
Hospit al (Australi a) was conducted by Aithal et al , (2012). A tot al of 211 infants att ended the
diagnost ic appoint ment for which review ap point ments to monit or hearin g statuses wer e
compl eted for 46 infants with middle ear pathol ogy or conducti ve he arin g loss . Of the 69 infants
presenti n g with middle ear pathol o g y du ring ini ti al diagnost ic assessme nt, 18 had middle ear
pathol og y with normal hearin g, 47 had conducti v e he arin g loss , and 4 had mix ed hearin g loss .
Prevalenc e of condu cti ve he arin g loss in the newborns was alm ost 0.3 % while prev a lence of
middle ear pathol o g y (with or without conduct ive hearin g loss ) was over 0.4%. A stud y b y
Amedofu et al (2005) revealed that, condu cti ve loss es were mainl y att r ibut ed to oti tis media,
wax , foreign bodi es and t rauma in Ghan a.
2.3.2 Sensorin eu ral Hearin g Loss
S ensorineural he arin g lo ss (SNH L) oc curs wh en there is dama ge to the in ner ear (cochle a) or to
the nerve pathw a ys from the inner ear to the brain . Most of the time, SNHL cannot be medicall y
or surgi call y corr ected. This is the most comm on t ype of permanent he a ring loss . This t ype of
hearin g loss reduces th e abil it y to hea r faint sounds. Even when spee ch is loud enough to hea r, it
ma y sti ll be uncl ear or so und is muffled. Some po ssi ble causes of SNH L ar e illnesses, dru gs that
are tox ic to hearin g, gen eti c or heredit ar y, agin g, head trauma, malformati on of the inner ear and
ex posure to loud nois e.
Adult onset hearing loss was not separatel y anal yz ed in the Global Burde n of Disease for 1990.
The leadin g cause of adu lt onset hearing loss was pre sb ycusis (age -rel ated hearin g loss ) followed
by nois e-induced he arin g loss (Mathe rs et al . , 200 0). WHO has identified middle ear infe cti ons,
ex cessi ve noise, inappropriate use of certain drugs, problem durin g chil dbirth and vaccine
University of Ghana http://ugspace.ug.edu.gh
1 2
preventable inf ecti ons as the major preventable ca uses of hearin g impairment in low and middle -
income countries.
A stud y was condu cte d by Amedo fu et al., (1997) to determi ne the causes of dea fn ess in Kumasi
(Ghana ). A tot al of 128 deaf chil dren aged bet ween 1 -5 ye ars refer r ed to the Ear, Nose and
Throat (ENT) Cli nic at the Komfo Anok ye Teac hing Hospit al (KATH ) were se en from J anuar y
1992 to June 1993. The procedur e adopted incl uded ex plorati on and assessment of indi vidual
medical hist or y, otoscop y, pre - audiom etric and audiom etric evalu ati on. The res ear che rs found
out that 66(51.5%) of the participants had con ge nit al sensorineural hea ri ng loss (CS H L), while
the remainin g 62(48.5% ) had acquir ed senso rineu ral hea ring loss (AS H L). Of the 66 con genit al
cases, 44 were due to unknown fact ors, while the rest were du e to post -natal convuls ion,
measles, menin git is, mum ps, fever and j aundice. Result s of fre e -fi eld tests wer e av ail able in 11 6
chil dren. Of these, 90 cases had a profound S NH L of whi ch 56 wer e due to congenit al factors ,
while 38 had a sev ere -p rofound SNH L and the remaining 34 ori ginated from acquir ed causes.
Thus, the cases listed under CSH L showed a dist inctl y hi ghe r incidence of profound deafness.
The stud y con cluded pri mar y preventi on measu r es against diseases that cause d de afness as the
most logical and practi ca l wa y of redu c in g the inc iden ce of deafn ess in Gh ana.
Another stud y condu cte d by Amedofu et al , (2 005 ) on 6,428 pati ents who visi ted t he ENT
Department at KAT H revealed that, th e ove rall prevalen ce of SNH L was mor e than othe r t ypes
RI KeaUing ORVV. 1RiVe IeYeU SUeVE\FXViV PeningitiV and 0enieUe¶V diVeaVe ZeUe tKe PaMRU
causes of SNH L. Condu c ti ve hearin g loss was att r ibut ed mainl y to wax , oti ti s media, meningit is,
rubell a, con genit al anomalies and non -s yndromal inherited hea ring loss .
University of Ghana http://ugspace.ug.edu.gh
1 3
2.3.3 Mixed Hearin g Loss
A mix ed hearin g loss oc curs wh en both sensorin eural and condu cti ve impairments coex ist in the
same ear. It ma y be caus ed b y the pres ence of tw o separ ate disord ers in th e same ea r (e. g., noise -
induced hea ring loss plus oti ti s media) or by a single disorde r that aff ect s the conducti ve and
sensorineural s ystems such as otosclerosis (Gelfa nd, 2009). A report by ASHA on the incidence
and prev alenc e of hear ing loss and he arin g aid use in the United States reve aled th at,
authorit ati ve data conc er ning the gene ral incid en ce and pr evalen ce of mix ed hearin g loss are
unavail able in the all ied healt h or medical lit er ature (AS HA, 2008 ).
2.4 DEGREE OF HEARING LOSS
The seve rit y of a hearin g loss depends on th e degree of loss . A pure -tone ave ra ge (PTA) is
usuall y calcul ated for each ear. The PTA, which is sim pl y the mean of the air -conducti on
threshol ds at 500, 1000 and 2000 Hz, is an att empt to summ ariz e th e degree of hearin g loss
(Gelfand, 2009). Cate go ries t ypicall y us ed to describe the de gre e of hearin g loss at KBTH
Hearin g Ass essm ent Center ar e pres ented in Table 2.1.
Table 2.1 : Degre es of hearin g loss used at the KBTH
Pure tone ave rage (in d BHL) Degree of hearin g loss
- 5 to 25 dB HL Normal hea ring
26 - 40 dB HL Mild Hearin g Loss
41 - 55 dB HL Moderate Hearin g Loss
56 - 70 dB HL Moderate - S ev er e Hearin g Loss
71 - 90 dB HL Severe Hearin g Loss
>90 dB HL Profound Hea ring Loss
University of Ghana http://ugspace.ug.edu.gh
1 4
Amedofu et al., (2003) indi cated that, of the14 5 respondents found wit h hearin g impairment
gr eate r than 25dB HL, 66.9% ( n=97 ) had a mild hearing impairme nt, 17.9% ( n=26 ) had
moderate he arin g impairment, while 7.6% ( n= 1 1 ) each had s ever e hea ring impairment , and
profound hearin g impair ment. The majorit y of people therefor e had mild hearin g impairment. A
related stud y conducted by Mar fo, (2009) on the prevalen ce of hearin g impairment at the Offinso
Municipali t y of Ghana revealed that o f 135 respo ndents found wit h he arin g impairm ents gre ater
than 25dB H L. The ma jorit y of the respondent s (42%, n =57) had mild hearin g impairment ,
where as minorit y of the m (4%, n=6 ) had profou nd hearin g impairment. Fort y participants (30% )
were found to hav e moderate hearin g impairmen t, 11% ( n=15 ) had mode ratel y seve r e he arin g
impairment, and 13% ( n =17 ) pres ented wit h seve re hea rin g impairment .
2.5 GENDER DISTRIBUTION OF HEARING LOSS
Accordin g to the Nati onal Insti tut e on Deafn ess and other Comm unicati on Disorders (NIDCD ),
men are twice as lik el y t o develop hearin g loss as women, especiall y me n between the ages of
20 -69 ye ars. Men tend to lose hearing in the higher frequ encies first, whi le women tend to lose
hearin g in the lower freq uencies first. But the re has been inconsist enc y in various studi es cit in g
gend er as a risk factor for hearin g loss . Whil e some have found females to be at a hi gher risk,
others have not found thi s to be the case (Ake em et al, 2010).
A cross-se cti onal and lo ngit udinal population stud y of hearin g loss and speech discrim ination
scores by Moller (2006) in an unselected population of indi viduals aged 70 showed that both
these groups of indi viduals had speech discrim i nati on scores somewhat lower in men than in
women. Ex posure to noise affe cted he arin g in men more than in wom en and app ear ed as a
sli ghtl y gr eate r he arin g l oss for high frequenci es. The reas on for th ese gen der diff eren ces ma y be
University of Ghana http://ugspace.ug.edu.gh
1 5
that man y men hav e noise -induced he arin g loss (NIH L) , but there ma y be other factors related to
hormonal influenc e on the pro gressi on of age - related chan ge in the cochlea and possi bl y
differen ces in the age- r elated ch an ge in the neural pro cessi n g of sounds. Another stud y b y
Agraw al et al, (2008) to determi n e hearin g l oss prevalenc e amon g U. S . adult s evaluated
differen ces b y demo gr a phic chara cterist ics and known risk factors for hearin g loss (smoking,
noise ex posure, and card iovascular risks) and esta bli shed that o dds of hearing loss were 5.5 -fold
higher in men than women. Othe r indi cati ons of high prevalen ce of h ea ring loss amon g persons
older than 70 years hav e been repo rted (Helz ner et al, 2005) while other studi es (Bor ch grevink et
al, 200) have described t he gradual o r non-li nea r dependen ce of preval enc e with age.
Neverthel ess, there hav e been conflicti ng studi e s on the prevalence stu dies among men and
women in Ghana. In par ti cular, the Nati onal Aca dem y on An Agin g Soci et y (NAAS ) reporte d
that men of all ages are more likel y than women to have hea ring loss (Fi g. 2.1) (NAAS , 1999).
Fig. 2.1: Prevalence of hearin g loss by age grou p and gend er (Source: Nation al Academy on
an Aging Society. Analysi s of data from the 1994 Nation al Health Interview Survey of
Disabil ity, Phase I, 1994).
0.6
2
3
10
0.8
3
8
19
0
5
10
15
20
25
30
35
0- 17 18 -44 45 -64 65 +
P
e
rc
e
n
t
Age (yrs)
Male
Fe male
University of Ghana http://ugspace.ug.edu.gh
1 6
A stud y conducted b y Marfo (2009) on the pr evalenc e of hea ring imp airment at t he Offinso
Muni cipalit y indi c ated th at out of 135 respondents with hearing impairme nts, 44% ( n =59 ) wer e
female while 56 % ( n = 76 ) wer e male. Th e sa me observati ons hav e also been detailed b y
Cruikshanks et al , (1998) , and further af firmed b y Wil son et al (2010). In contrast, Amedofu et al
(2005) rev ealed that the r e wer e more hearin g imp aired females than males in a differ ent stud y.
2.6 AGE DISTRIBUTION OF HEARING LOSS
2.6 .1 Age Relat ed Hearin g Loss
Age relat ed hea ring los s (p resb ycusis ) is a bilat eral loss of audit or y sen sit ivi t y that pro gr esses
from high to low frequen cies with ageing. Howev er, the rate of hearin g de cli ne is not linear and
is highl y va riable, and th e varian ce in hearin g lev el is onl y weakl y asso cia ted with age. Hea ring
loss is a comm on disorder associated with aging and is ranked as th e thi rd most prevalent chroni c
condit ion in elderl y peop le after h yp ertension and arthrit is. Its pr evalen ce and severit y incr eas e s
with age, risin g from abo ut 30 -35% of adult s aged 65 year s and old e r to an esti mated 40 -50% of
adult s aged 75 and older (Cruikshanks et al., 199 8). Thes e obse rvati ons s uggest that age -r elated
chan ges do not occur uni forml y and that more th a n one pathol o gical pro ce ss ma y be acti ng upon
the audit or y s ystem. This variet y ma y also be taken as indi rect evi dence of th e compl ex
int eracti on of geneti c an d environmental factors in the eti ology of pr esb yc usis . Addin g to the
compl ex it y, both the pe ripheral and centr al auditor y pathwa ys can be aff ect ed in presb ycusis .
In Austr ali a, preval ence rates for hea ring loss are associated with increasin g age, risin g from less
than 1% for people aged youn ger than 15 years to 75% for people aged over 70 years. Wit h an
agein g population, hearing loss is projected to increas e to 1 in ev er y 4 Australi ans by 2050.
Studi es by Agr awal et al , (2008) on 5742 adult s aged 20 to 69 years who participated in the
University of Ghana http://ugspace.ug.edu.gh
1 7
audiom etric compon ent of the United States Nati onal Healt h and Nutriti on Ex ami nati on Surve y
from 1999 to 2004 reve aled that in the youn gest age group (20 -29 ye ars ), 8.5% ex hibi ted hearing
loss and the rest were among the older age grou ps which indi cat ed highe r prevalenc e . The same
observati on has been rep orted by Lee et al, (200 5) and confirmed b y Cu rhan et al, (2010) that
the prev alenc e of hea rin g loss in cre ases with age , with hea ring threshol ds worsen in g on av era ge
b y 1 dB per yea r afte r age 60 years, and de cli ne rate s gr eate r in men aged 48-59 ye ars.
Verr as and Matt os (2007) identified presb ycusis as the most frequent cause of hearin g loss in the
elderl y in Br az il , causing verbal comm unicati on i mpairment , and discover ed that the preval ence
of presb ycusis int er ferin g in the life qu ali t y of th is populati on increased with increasin g number
of elderl y people. This stud y agr ees with 0aUIR¶V ZRUN which reported that o ut of 135
respondents in Ghana , 28% ( n= 3 8 ) b e longed to the 0 ±20 ye ars group, 8% ( n=11 ) were aged 21 ±
40 ye ars, 20% ( n=27 ) were aged 41 ±60 ye ars, and 22% ( n =59 ) were above 60 years. Othe r
publi shed articles (NAA S , 1999) have confirmed same and particularl y emphasiz ed that hearing
loss is highl y asso ciated with agin g.
2.6 .2 Hearin g Loss in Children
Undetected hearin g loss in infants and youn g chil dren compromi se s opti mal langua ge
developm ent and person al achiev ement. How eve r rese arch demons trates t hat when he arin g loss
is identified ea rl y (p rior to 6 mont hs of a ge) and followed immediatel y (withi n 2 mont hs) with
appropriate int erventi on services, th e outcome in lan gua ge developm ent, speech developm ent,
and social-emot ional dev elopm ent wil l be signific antl y bett e r (Yoshina go ±Itano et al., 1998 )
University of Ghana http://ugspace.ug.edu.gh
1 8
A stud y condu cted b y Amedofu and Brobb y (det ermined the prev alenc e of hearin g-im pairm ent
among pr e-school chil dr en in Kumasi, Ghana. A tot al of 960 chil dren were scr eened usin g
audiom etr y and otoscopy. The stud y rev ealed th at 8.2% ( n=79 ) chil dren fail ed the audiom etric
screenin g test and were refer red for cli nical ex ami nati on. Onl y 48.8 % ( n=3 7) report ed for furthe r
evaluation and 72.9% ( n =27 ) were found to h ave a hearin g loss gr eater th a n 25 dB HL.
Epidemi ological dat a on the prevalen ce of hearing impai rment in chil dren indi cate that in
developi ng count ries , ear l y newborn hearin g scr e ening pro grams are be en conducted in var ious
countries. This is beca use signifi cant hearin g loss is one of the most comm on major
abnormali ti es pr esent at birth . KBT H has started a neonatal hea ring sc re ening pro gr am fo r all
babies including those at the Neonatal Int ensive Care Unit (N IC U ).
2.7 UNILATERAL AND BILATERAL HEARING LOSS
Unilateral hea rin g loss (UH L) occu rs when the hearin g in one ear is within normal limi ts and the
other ear has a hearin g l oss ran gin g from mild to profound. Indivi duals with unil ateral hearin g
loss ma y have troubl e locali z ing sounds . Lo cali z ati on is important when listening in groups of
people and is helpful in i denti f yin g who is talki n g at an y mom ent as well as for safet y. Another
effe ct is difficult y in und erstandin g spe ech in noi s y sit uati ons. Two no rmal hearin g ea rs help to
filter out noise to hear sp eech bett er. An indi vidua l presenti ng with a UHL can often hear sp eech
from a dist ance, but ma y not alwa ys understand what is being said.
The impact of UHL on the acad emi c perform anc e was investi gated b y Oyl er et a l (1988). The y
in vesti gated a school dist rict of 54,000 students and found out that 106 students had a UHL. A
review of their academi c perform ance provided evidence that a unil ateral hearin g loss can pl ac e
University of Ghana http://ugspace.ug.edu.gh
1 9
a chil d at risk for academi c fail ure, espe ciall y whe n in the severe- t o -p rofound ran ge and/o r
invol ving the ri ght ear.
ASHA esti mates that approx im atel y 1 out of ever y 10,000 chil dr en is born with a UHL, and
nearl y 3% of school -a ge chil dren have UH L. Studi es investi gati ng purel y UH L in other countries
have found a much lower prevalenc e of 3 % in adult s with conducti ve loss es being more comm on
than sensorineural heari ng loss (Al Khabo ri and Khandeka r , 2007 ). Singl e-sided sensorineur al
hearin g loss has an esti mated incidenc e of 9,000 cases a year (Ba gul e y et al . , 2006).
Bilat er al hea ring loss oc curs in both ears. It is esti mated that more tha n 1.2 mill ion chil dren
between the ages of 5 and 14 have a mode rate t o severe bil at eral he arin g loss in sub Saharan
Africa (McP herson, 1997 ).
2.8 COMMON CAUSES OF HEARING IMPAIRMENT
Most congenit al and chil dhood onset of hearin g lo ss is caused b y various di seases includ ed in the
Global Bu rden of Dise as e Stud y. Ex ampl es include oti ti s media, menin git is, rubell a, con genit al
anomalies and non-s ynd r omal inherit ed he arin g lo ss. Adult onset hearin g l oss was not sepa ratel y
anal yz ed in the ori gi nal Global Burd en of Dise as e for 1990. Th e leadin g causes of adult onset
hearin g loss ar e presb yc usis (age rel ated -he arin g loss ) followed by noise -induced he arin g loss
(Mathers , Smi th and Concha, 2000).
2.8 .1 Occupation al Noise Exposu re
Noise-induced hearin g l oss (NIH L) is an irr eve r sibl e sensorineural he ari ng loss associated with
ex posure to high levels of ex cessi ve noise (Kit c her et al, 2012) and thi s is one of the most
University of Ghana http://ugspace.ug.edu.gh
2 0
comm on and most compl ex and far -re achin g problem in the healt h and safet y empl o ym ent
haz ards in both indus trializ ed and developi n g countries (Amedofu, 200 7). One of the most
predispo sing factors to NIH L is occupati onal noise. Occupati onal noise is a frequentl y
encounter ed on-the- j o b.
WHO reported the fra cti on of adult -onset hearing loss att ributable to occupati onal noise
ex posure and indi cated per its global anal ysis that 16% of deafn ess was due to occupati onal
noise, wit h a hi gher pro portion (22%) in males than in femal es (11% ) owing to dif fer ences in
occupati onal cate go ries, economi c sectors of empl o yment and workin g lifeti me (WHO, 2004).
Approx im atel y 89 % of the tot al NIH L burden is found in persons in the 15-59 ye ar age group,
with the remainin g 11 % are ov er 60 yea rs . Ove ral l, more than four mill ion disabil it y adjust ed life
ye a rs (DA LYs) wer e lost to noi se -induced he arin g loss (W HO, 2004).
A stud y condu cted b y Boaten g and Amedo fu (20 04) on indus trial noise poll uti on and its effect
on the hearing cap abil it ies of workers in saw mil ls, printing presses and corn mill s in Gh ana
showed that such work e rs wer e ex posed to haz ardous noise. Result s fro m their stud y indi cated
that 22.9% of corn mill workers, 20.5 % of work ers in saw mill s and 8% of worke rs in print in g
presses had hi gh frequ en c y he arin g loss at 4 k Hz which is consi stent with noise - induced hea rin g
loss . Another stud y was car ried out b y Amedo f u ( 2004 ) to determi ne th e impact of haz ardous
noise on workers in a sur face gold minin g compa n y in Ghan a. The pro ced ure adopted includ ed a
noise surve y, case hist or y, otoscop y and conve nti onal pure -tone audio metr y. Five main areas
were surve ye d for haz ar dous noise . The result s showed that four ar eas produced noise lev els
above 85 dBA. Of the 252 workers at the compan y, 23 % ( n=59 ) had a typical noise -indu ced
hearin g loss at 4 kHz.
University of Ghana http://ugspace.ug.edu.gh
2 1
In a stud y to assess the prevalen ce of earl y NIH L and the aw aren ess of t he eff ects of noise on
healt h amon g stone crus hing indus tr y wo rkers in Ghana, Kitcher et al., (2 012) noted that 87.5%
of the stone crushin g wo rkers had sound knowled ge on the healt h haz ards of workin g in a nois y
environment. How ever, the rese arch ers posi t ed t hat onl y 5.5 % of th ese workers actuall y use d
hearin g prote cti ve devic es even thou gh the nois e levels at their wo rk st ati ons, ex cludi ng the
admi nist rati ve offices, ranged betwe en 61.2 dB(A) and 99.6 dB(A). Kit cher et al., (2012 )
concluded th at work ers in the stone cr ushi n g indus tr y wer e ex posed to haz ardous noise, which
was contribut or y to the high prev alenc e of earl y noise -induced senso rineur al hearin g loss .
2.8 .2 Otitis Media
In flamm ati ons of the middle ear ar e call ed oti ti s media and const it ute the most comm on ca use of
conducti ve hea rin g loss . Otit is media affects peop le of all ages, but the incidence amon g chil dren
is particularl y hi gh (Ge lfand , 2009 ). It is the most comm on medical diagnosi s for chil dren
accounti n g for 6 mill ion office visi ts in 1990 for chil dren betwe en the age s of 5 and 15 yea rs in
the United States (Stol l and Fink , 1996). Adul ts too ma y have oti ti s media with ef fusion,
alt hough the pr evalenc e decr eases signi ficantl y with age (Fria et al, 1985 ). Katz et al, 2009
posi ted that, during the acti ve infecti on of oti ti s media, a pati ent ¶s heari ng loss ma y flu ctuate,
usuall y va r yin g betwe en 0 and 40 dB. Th e ave ra ge de gre e of hearin g loss is approx im atel y 25dB.
A prospecti ve cross -secti onal stud y conducted b y Awuah et al, (2012 ) on 51 pati ents at KATH
showed that, hearin g lo ss occurs in majorit y of suffe rers of acute oti ti s media (A OM). Th e
prevalen ce of AOM was low in adults but high in children (91.3% ).
University of Ghana http://ugspace.ug.edu.gh
2 2
2.8 .3 Impacted Cerumen
This is an accumul ati on of wax in the ear can al that int erfe res with the flow of sound in the
eardrum. It occu rs natur a ll y in man y pati ents who produce ex cessi ve amou nts of cerum en, which
buil ds up over time (Gelfand , 2009 ). Impa cted ce rumen comm onl y produ c es conducti ve he arin g
loss , itching, tinnit us, ver ti go and ex ternal oti ti s. The he arin g loss wo rsens as the cerum en buil ds
up, and can rea ch 45dB when the canal is comple tel y oc cluded, Gelfand (2 009).
2.9 CLINICAL PROCEDURES FOR DETERMINING HEARING LOSS
2.9.1 Pati en t History Intake
It is ver y important for a cli nician to take an ex tensive hist or y of th e pati en t . This will enable the
cli nician to know wheth er there ar e predispo sin g factors of hearin g los s and also which test
batt er y will be empl o yed (Katz et al ., 2009 ).
2.9.2 Pure Tone Audio met ry
Audiometers are used to make quanti tative measures of air condu cti on (AC) and bone
conducti on (BC) thr eshol ds. AC threshol ds asses s the enti re audit or y pat hwa y and ar e usuall y
measured using ea rphon es , BC th reshol ds are m easured b y pla cin g a vibrator on the skul l. Its
goal is to bypass the outer and middle ears and sti mul ate the cochlea directl y. When sound is
deli vered b y an earphon e, the hearin g s ensit ivi t y can be sep arat el y assess ed in each ear (Katz et
al, 2009).
2.9.3 Otoacoustic Emission s
Otoacoust ic emi ssi ons (OAEs) ar e sounds that ar e produced b y the cochle a in the ear and can be
measured usin g sensit ive microphones plac ed i n the ear canal (Gelfand, 2009) . Kemp (1979)
University of Ghana http://ugspace.ug.edu.gh
2 3
dePRnVtUated tKat 2$(¶V aUe produ ced eit her sp ontaneousl y with out an y sti mul ati on or evoke d
from the co chlea. Ener gy produced b y outer hair cell mot il it y serv es as an ampl ifier withi n the
cochlea, contribut ing to bett er hea rin g. OAEs ar e produced b y the ene r gy from outer hair cell
mot il it y that makes its wa y out w ard from the cochlea throu gh the middle ear, vibra ti n g the
t ympanic membr ane, an d propagati ng int o the ex ternal ear canal. Norm al outer hair cell s are
therefor e essential for pe rfectl y normal audit or y functi on.
Two t ypes o f OAEs may be measur ed cli nicall y. These are transient -evo ked OAEs (TEOAEs )
and diVtRUtiRn SURdXFt 2$(¶V (DPOAEs). TE OAEs are produced in response to ver y brief
(trans ient) sti mul i , such as cli cks or tone bursts, presented usuall y at an int ensit y lev el of 82 -83
dB SP L (Gelf and, 2009 ) . TEOAEs refle cti ng cochlear (outer hair cell ) acti vit y are gene rall y
record ed over the freq uenc y ran ge of 500 to about 4000 Hz. DPOAEs are eli cit ed b y
sim ult aneousl y presenti n g to the ear two sti mul us tones of different freq uen cies abbr eviated f2
and f1, th at ar e clos e l y spaced and pres ented sim ult a neousl y at mod e rate in tensit y lev els .
DPOAEs can be record e d across a frequenc y region of 500 to 8,000 Hz and someti mes even
higher frequ encies .
OAEs are non-inv asive and technicall y sim ple to record, usuall y requiri ng onl y a few min utes
for both ears. Sedati on is not indi cated for OAE measur ement, eve n in chil dren. It is a
ph ysiol o gic me asure tha t does not requir e coop e rati on . Durin g OAE test ing, a soft dispo sable
probe tip is gentl y inse r ted int o the outer portio n of the ex ternal ear ca nal . An ai rtight s eal
between the probe tip and the ear canal is not necessar y. A miniature spe aker withi n the probe
assembl y (two spe akers for DPOAEs) gene rates in the ear can al sound s ti mul i at a moderate
int ensit y lev el. The sti mul i vibrate the t ymp anic membrane and me chanic al ener g y is transmi tt ed
University of Ghana http://ugspace.ug.edu.gh
2 4
through the middl e ear to the co chlea. Tin y waves in the co chlear flui ds vib rate a thi n membr ane,
acti vati ng oute r hair cel ls located on the membrane. Ene r g y associated with outer hair cell
movement, in the frequ e nc y region of th e sti mul us, is propa ga ted ba ck t hrough the middle ea r
s ystem and, as sound, i nto the ear canal. A mi niature microphone with in the probe as sembl y
detects OA E-r elated sou nd, as wel l as an y othe r sound in the ear canal during th e recordin g
(Gelfand, 2009 )
:Ken 2$(¶V aUe aEVent it Pa\ RU Pa\ nRt indiFate a SUREOeP ZitK KeaUing. A stud y was
conducted b y Abd el -Ha mi d et al , (2007) in Eg ypt . OAE was used to scr een 4,000 indi viduals.
Those that fail ed the test were 19.81 % and they were refer red for fu rther evaluation. Hearin g
loss was detected in 16.2 %.
2.9.4 Tympan o met ry
T ympanomet r y invol ves measuring the acoust ic admi tt ance of the ear wi th various amount s of
air pressu re, Gelfand (20 09). Acoust ic admi tt ance is the eas e of sound flo w throu gh the middle
ear and acoust ic impedance is the opposi ti on of flow of sound energ y. T ympanometr y the refo re
is a clinical proc edur e that measures middle ear pressur e. The ins trument used is the
t ym panomete r and the gr aph drawn is known as a tympano gr am.
Ear canal pressu re is ex pressed in unit s call ed deca -P as cals or daP a. As air pressur e in the ear
canal is incre ased or dec reased f rom atm ospheric condit ion (0 daP a) in a person with a norm al
middle ear, the acoust ic admi tt ance is decr eased or the acous ti c imped anc e is incr eased. In cases
of disorders that damp e n or sti ffen the middle ear s ystem, such as ser ous oti ti s media with
effusion , the t ymp ano gra m ma y be redu ced in ampl it ude or flat in confi g ur ati on. In contrast, a
University of Ghana http://ugspace.ug.edu.gh
2 5
disconti nuit y of the oss icular chain will be associated with a t ympano gr am havin g greater
ampl it ude than normal (W il e y and Fo wler, 1997) .
2.10 CONCLUSION
From the literatur e revi e w, one can s ee that so me prevalen ce studi es have be en conduct ed at
KATH, but none have be en conduct ed for the KBTH . Ther e is ther efor e he need for such a stud y
to be conducted. Th e met hodolog y adopted for thi s stud y is present ed in the nex t Chapter.
University of Ghana http://ugspace.ug.edu.gh
2 6
CHAPTER THREE
METHODOLOGY
3.1 INTRODUCTION
This Chapter describes t he approa ch empl o yed i n conducti ng the rese arc h. It includes the stud y
design, stud y area, stud y population, sampl ing design, data coll ecti on tec hniques, and resea rch
inst rument and data an alys is.
3.2 STUDY SITE
The Hearin g Assessm en t Center of KBTH was chosen as the stud y sit e . The Center serves a
population of over 4 mil li on living in Great er Accr a Re gion and all other pati ents who ar e
refe rred from other regio nal h o spit als for hearin g assessment.
3.3 STUDY DESIGN
This rese arch was a retro specti ve stud y which revi ewed ex ist ing data to det ermine the prev alenc e
of hearin g impairm ent from J anuar y 2012 - Dec e mber 2012 at KBTH. Th is covers a tot al pe riod
of one yea r. The stud y assess ed the number of people wit h hearin g impai rment over that pe riod
of time and focus ed on t he audiom etric confi gu ra ti on, t ype and de gre e of hearin g loss and their
correl ati o n with gend er and age. The vari ables stu died are indi c ated in Tabl e 3.1
University of Ghana http://ugspace.ug.edu.gh
2 7
Table 3.1: Study v ariables
Study Variab les
Age Prevalenc e of hearin g los s among the design ated ages o f 0 - 9, 10 - 19, 20 -
29, 30 - 39, 40 - 49, 50 - 59, 60 years and above
Gender Prevalenc e of hearin g los s among males and fem ales
Degre e of hearin g
loss
Prevalenc e of the various degrees o f hea rin g loss - mild, moderate,
severe, profound, mild to moderate, et c.
Configur ati on Prevalenc e of the various configu rati on of hearin g loss - conducti ve,
sensorineural and mix ed
Unilateral ve rsus
bil ateral hea ring loss
Prevalenc e of unil ater al and bil ate ral hea rin g loss e s
Tympano grams Prevalenc e of the various t ypes - t yp es A, As , B, C and D
OAE The pass and refe r rat e s
3.4 SAMPLING
The stud y in cluded a ret rospecti ve revie w of the records of all pati ents who visi ted the Hearing
Assessm ent Center fro m J anuar y 2012 - Dec e mber 2012. All pati ent reco rds were revi ewed
regardl ess of age or gend er of the pati ents.
3.5 SAMPLE SIZE
Bec ause the stud y is a retrospecti ve stud y, the sampl e siz e cannot be calculated usin g pa ra
anal ysis or a statis ti cal formul a . All the pati ents who visi ted the facil it y during the pe riod of
stud y will form the samp le siz e.
University of Ghana http://ugspace.ug.edu.gh
2 8
3.6 PROCEDURE FOR DATA COLLECTION
All the audiograms of pati ents visi t ing the Hearing Assessm e nt Center were coll ect ed and
anal yz ed. Th e pro cedur e used was ther efor e an all -inclusi ve criterion .
3.7 INCLUSION AND EXCLUSION CRITERIA
3.7.1 Inclusion Criteria
All pati ents who visi ted the Hearin g Assessm ent Center of KBTH from J anuar y 2012 to
Decemb er 2012 were inc luded in the stud y.
3.7.2 Exclusion Criteria
All pati ents who att ended the assessment Center at periods outsi d e J anuar y 2012 to Dec ember
2012 were ex cluded fro m the stud y.
3.8 RESEARCH TOOLS
3.8 .1 Audiograms
The audio grams of pati ents who visi ted the Hearin g Assessm ent Cent er durin g the per iod
covered b y the stud y we re reviewed. The audiogram is a graph showin g t he result s of the pure -
tone hearin g tests. It illust rates the t yp e, de gre e, and audiom etric confi gu rati on of hearin g loss .
The frequen c y or pit ch of the sound is ref err ed to in Hertz (Hz ). Th e int en sit y or loudn ess of th e
sound is measured in dec ibels (dB).
Each vertical line from left to ri ght repr esents a pit ch, or frequen c y, in Hertz (Hz ). Th e gr aph
starts with the lowest pitches on the left side and moves to the ver y hi ghes t pit ches (frequen cies)
University of Ghana http://ugspace.ug.edu.gh
2 9
tested on the right side. The ran ge of frequenci es tested by the audiol ogis t are 125 Hz, 250 Hz,
500 Hz, 1000 Hz, 2000 Hz , 3000Hz , 4000 Hz, and 8000 Hz (Fig.3.1 ).
Fig. 3.1: Audio met ric configu ration of hearin g loss (Source: www.ASHA.org )
Audiogr ams are often classified b y cate go ries based on the degr ee of hearin g loss . Th e
frequen cies used for thi s purpose are usuall y 50 0, 1000 and 2000 Hz , often refe rred to as the
three frequ enc y pu retone aver a ge (Katz et al . , 20 09). Althou gh KBTH se ts the upper limi t for
normal hea ring at 25 dBH L, Northe rn and Down s (2002) su ggest usin g 15 dBH L as the upper
limi t for normal hearin g for chil dren betw een 2 an d 18 years of age and a higher limit for adult s.
Another wa y of classif yi ng audio gr ams is by the t ype of hearin g loss (Katz , 2009) . The t ype of
hearin g loss is determi ne d by compa rin g th e amo unt of hearin g loss for ai r conducti on and bone
conducti on threshol ds. A sensorineu ral hearin g loss has an equ al am ount of loss fo r AC and BC
threshol ds (Fig.3.2 ). B y contrast, a conducti ve hearin g loss has bett er BC threshol ds than AC
University of Ghana http://ugspace.ug.edu.gh
3 0
threshol ds. The degree of conducti ve loss is described by the decib el differenc e betwe en air and
BC threshol ds (Fi g.3.3 ).
Fig. 3.2: An audiogra m of sensorin eu ral hearing loss
Fig. 3.3 Audiogra m of conductive hearin g loss (Source: OSHA)
A mix ed hearing loss has an air - bone gap and threshol ds for BC fall s outsi de the range of
normal hea ring (Katz et al . , 2009) and look s at what is repr esente d below (Fi g.3.4).An
University of Ghana http://ugspace.ug.edu.gh
3 1
audiogr am is summ ariz ed verball y b y the degre e, t ype and audiom etric configu rati on of the
hearin g loss fo r both ea r s (Katz et al., 2009). A hearin g loss oc currin g in one ear is known as a
unil ateral hea ring loss and if it occurs in both ears it is described as a bilateral hearin g loss
(Gelfand, 2009 ).
Fig 3.4 A udiogra m of a mixed hea rin g loss
3.8 .2 Tympan ogra ms
T ympano grams ar e class ified acco rdin g to the ear canal volum e, the static compl iance, the peak
pressure and the gr adient . The equivalent ear can al volum e (ECV) is an esti ma te of the volum e
of air medial to the prob e, which includes the vo lum e between the probe tip and the t ympanic
membrane if the t ympani c membrane is int act, or the volum e of the ear canal and the midd le ea r
space if the t ymp anic membrane is perfo rated (Fowler & Shanks, 2002 ). Tympanomet ric peak
University of Ghana http://ugspace.ug.edu.gh
3 2
p ressure (TTP) or middl e ea r pre ssu re (MEP) is the ear can al pressur e at which the pe ak of the
t ympano gr am oc curs (M ar goli s & Hunt er, 2000). Static compl iance (S & ³iV tKe gUeateVt aPRXnt
of acoust ic ene r g y abso r bed b y the middl e ea r s ys tem (the ve rtical p eak of the t\PSaniF tUaFing ´
(Onusko, 2004 ).
Type A t ymp ano gr ams have a dist inctive peak in the vicinit y of atm ospheric pressur e and are
t ypical of no rmal pati ent s as well as those with otosclerosis. If the t ype A tympano gr am has a
shallow peak, it is classified as As which is gen er all y associ ated wi th otosclerosis, but ver y deep
t ype A tymp ano grams ar e desi gnated as t yp e AD. Typ e B t ympano grams have a flat atm ospheric
pressure and are ch ara ct eristi cs of pati ents with middle ear fluid and per forati ons or impacted
cerumen. T ype C t ympa ongr ams have a ne gati ve pressur e and ar e assoc iated with eustachi an
tube disorders and also in cases of middl e ear flui d (Gelfand, 2009 ).
3.8 .3 Otoacoustic Emission Results
2$( UeVXOtV aUe UeSUeVented aV eitKeU SaVV RU UeIeU. ³3aVV´ teVt UeVXOtV indiFate that OAEs are
present , and one can assu me the indi vidual's heari ng is at least 30 dB or bett er. If the re is damage
to the outer hair cell s pro d ucing a mild hearin g lo ss, then OAEs ma y not present. The test result
is "Refe r," and the pati e nt ma y be at risk for pos sibl e comm unic ati on handicaps and can bene fit
from further di a gnost ic assessment and possi ble rehabil it ati on (Northern and Downs , 1991 ).
3.9 DATA MANAGEMENT PLAN
The data in thi s stud y were m ana ged to protec t the identit y of the part icipants. The names of
pati ents wer e not us ed in the data anal ysis . Codes were used for th e various param eters as well as
the names of the particip ants. The codes wer e only man a ged b y the author .
University of Ghana http://ugspace.ug.edu.gh
3 3
3.10 ANALYSIS
The data were anal yz ed using the Statist ical Pac kage for Soci al Scientis t (SP S S ) version 16.0 .
The softwar e was used to comput e sim ple descriptiv e statis ti cs, perce ntages and frequenc y
tables. The cor relation between the various par a meters will also be esta bli shed. The preval ence
was calcul ated via the for mul a:
C
Hl
N
NP
(3.1)
where NHL = persons wit h hea ri ng loss durin g the spe cified time period
NC = number of people att ending th e cli nic duri ng the sp ecified peri od
3.11 ETHICAL CONSIDERATIONS
Ethi cal clear ance was obtained from the Ethi cs and Protocol Review Commi tt ee of the School of
Alli ed Healt h Sciences before the comm ence ment of the data collecti on. Permiss ion to
comm ence dat a coll ecti o n was granted b y the School of Alli ed Healt h Sciences (App endix III) .
Permiss ion to access pati ent data records was gr a nted by the head of ENT Department of KBTH
(Appendix II) . Assuran ce was given con cernin g co nfidentialit y with regard to handling data.
3.12 DISSEMINATION OF RESULTS
Per the requirem ents of the Unive rsit y of Gh an a, copies of the res ear c h diss ertati on will be
subm it ted to the Depart ment of audiol o g y of th e School of Alli ed Healt h Sciences. Th e findin gs
of the rese ar ch will be pu bli shed in professi onal journals .
University of Ghana http://ugspace.ug.edu.gh
3 4
CHAPTER FOUR
RESULTS
4.1. INTRODUCTION
The result s of the stud y are present ed in thi s Chapter. In particular the ke y or major aspects such
as demographics, t ypes of hearin g loss , audi ometric confi gur ati on of hearin g loss , OAE
evaluation and t ympano metr y.
4.2 DEMOGRAPHICS
4.2.1 Gender Demog rap h ics
7Ke gendeU diVtUiEXtiRn RI SatientV¶ att end ance to the Hearin g Assess ment Center for the is
repres ented in Table 4.1 . Out of the 715 pati ents who report ed to the KBTH Hea ring Assessm ent
Center, 51.9% ( n = 371 ) (51.9%) we re males and 48.1 (n =344 ) were female s .
Table 4.1: Gender dif f erence and Frequency of atten d ance of patients
Gender Frequency of atten d ance (numb e r) % atten d ance
Male 371 51.9
Female 344 48.1
Total 715 100.0
4.2.2 Age Demograp h ics
The frequ enc y of att enda nce of the various age di ffer en ces of pati ents as well as the dist ributi on
of hearin g loss (in both ears) amon g the va rious gend er and age cate gories ar e pres ented in
Tables 4.2 and 4.3 respe cti vel y. The most prev alent group of pati ents pr esenti ng with he arin g
loss to the cli nic whe re chil dren (35.9%, n =256 ) aged 9 years and below, whil e the prev alenc e of
University of Ghana http://ugspace.ug.edu.gh
3 5
adult s aged 50-59 ye ars , and above 60 yea rs wer e 11.1% ( n =79 ) and 8.4 % ( n=60 ) resp ecti vel y.
Pati ents wit h no recorded age demo gr aphics accou nted for 5.2% ( n = 38 ) of the populati on.
Table 4.2 : Age diff erence and freq u ency of atten d ance of patients
Age (yea rs) Frequency of atten d ance (numb e r) % atten d ance
0 ± 9 256 35.9
10 - 19 72 10.1
20 - 29 76 10.6
30 - 39 74 10.4
40 - 49 59 8.3
50 - 59 79 11.1
More than 60 60 8.4
Other 38 5.2
Total 715 100.0
Table 4.3 : Frequency distrib u tion of hearin g loss for gen d er and varyin g age catego ries
Pati ents with normal
hearin g
% att endanc e Pati ents diagnosed
with hearin g loss
% att endanc e
241 33.7 474 66.3
Demograp h ic variab le
Types of hearin g loss
Conductive
(a/b)
Sensorin eu ral
(a/b)
Mixed
(a/b)
Total
(a/b)
Gender Male 23/15 77/89 46/43 146/147
Female 21/14 97/103 42/51 160/168
Age (yea rs) 0 - 9 6/4 6/6 3/2 15/12
10 - 19 9/6 24/24 14/15 47/45
20 - 29 5/3 24/32 8/7 37/42
30 - 39 5/6 16/20 10/6 31/32
40 - 49 6/3 23/24 7/10 36/37
50 - 59 9/4 29/32 14/20 52/56
4/3 52/54 32/35 88/92
Le gend : a/b si gnifies Right Ear/ Left Ear
University of Ghana http://ugspace.ug.edu.gh
3 6
From Tabl e 4.3, 33.7 % ( n=241) of pati ents repo rting to the cli nic fo r he aring assessment had
normal he arin g while 66.3% ( n=474 ) wer e dia gnosed with he arin g los s. The most preval ent
hearin g loss fo r both le f t and ri ght ears was rec orded fo r pati ents aged 60 and abov e ( 88/92 :
conducti ve=4/3 ; sensorin eural= 52/54 ; mix ed=32/35). The 0-9 years group that showed the least
prevalen ce of hearin g los s (15 /12: conducti ve=9/6 ; sensorineural=24/24; m ix ed=14/15).
Per gende r, the result s fu rther show ed that the tot al prevalen ce of the hearin g loss cases for mal es
was 146/147 (conducti v e=23/15 ; sensorin eural= 77/89 ; mix ed=46/43) . Comparati vel y, a hi gher
prevalen ce of 160/168 number (conducti ve =21/ 14; sensorineural=97/10 3; mix ed=42/51) was
record ed for th e femal e population.
4.3 TYPES OF HEARING LOSS
The result s of the esti mated prev alenc e of t ypes of hearin g loss eva luated in both ears ar e
presented in Tabl e 4.4.
Table 4.4 : Prevalence of typ es of hearin g loss evalu ated for both ears
Type of h earin g l oss Frequency (f) Percent (%)
Normal (NH ) 168/159 35.4/33.5
Conducti ve (CH L) 44/22 9.3/6.1
Sensorineural (SNH L) 174/192 36.7/40.5
Mix ed (MH L) 86/93 18.1/19.6
Other 2/1 0.4/0.2
Total 474 100
Legend a/b si gnifies Right Ear/ Left Ear
Table 4.4 depicts that the most prevalent t ype of hearin g loss for both right and left ea r was
SNH L 36.7 %/40.5 %. Th e prev alence of MH L was 18.1%/19.6% while t he least prev alent was
University of Ghana http://ugspace.ug.edu.gh
3 7
C H L (9.3 %/6/ 1%). Pati e nts with NH were evalua ted for at 35.4 %/33.5 % both right and le ft ea r s
respecti vel y. Th e dist ributi on of the hearin g loss t ypes in bot h ears is shown in Fig 4.1.
Fig. 4.1: Distrib u tion of types of hearin g loss in both ears
4.4 AUDIOMETRIC CONFIGURATION OF HEARING LOSS
S everal pati ents pres ented with different con fi gur ati ons of hearin g lo ss in both ears. The
record ed statis ti cs and th e dist ributi on of evalu ate d de gre e of hea ring loss are present ed in Tabl e
4.5 and Fi g. 4.2 respecti v el y.
0
50
10 0
15 0
20 0
25 0
N H CHL SN H L MH L
F
re
q
u
e
n
cy
Type of hearing loss
Left ear
Right ear
University of Ghana http://ugspace.ug.edu.gh
3 8
Table 4.5: Audiometric configu ration of evalu ated hearin g loss for righ t and lef t ears
Degree of Hearin g Loss Frequency (f) Percent (%)
Normal 165/157 35.4/33.6
Mild 74/75 45.9/16.1
Moderate 20/8 4.3/1.7
Severe 6/12 1.3/2.6
Profound 31/39 6.7/8.4
Mild to Moderate 64/61 13.7/13.1
Mild to severe 18/21 3.9/4.5
Mild to Profound 7/6 1.5/1.3
Moderate to Seve re 45/47 9.7/10.1
Severe to Profound 32/37 6.9/7.9
Reverse slope 4/4 0.9/0.9
Total 466/467 100
Legend a/b si gnifies Right Ear/ Left Ear
Fig. 4.2: Degree of evalu ated hearin g loss in left and righ t ears
0
20
40
60
80
10 0
12 0
14 0
16 0
Fr
e
q
u
e
n
cy
Degree of evaluated hearing loss for elft and right ears
L eft ear
Righ t ear
University of Ghana http://ugspace.ug.edu.gh
3 9
From Table 4.5 , the mos t prevalent confi gur ati on s of evaluated he arin g loss were mild hearin g
loss (45.9 %/16.1 % ) and moderate he arin g loss (13.7 %/13.1 % ) for both ri ght and left ear s. This
was followed b y mild to moderate confi gurati on of hearin g loss (13.7 %/13.1 %). The thi rd most
prevalent con fi gurati on of hearin g loss was moder ate to sever e (9.7 %/10.1 %). The reve rse slope
was the le ast prev alent ( 0.9 %/0.9 %) fo r ev aluate d right and left ears. Th ere was 35.4%/33.6%
normal confi gurati on of hearin g loss for both ri gh t and left ea rs evaluat ed.
4.5 OTOACOUSTIC EMISSION AND TYMPANOMETRY ANALYSIS
OAE and t ympanometr y tests were conducted on the subj ects. The evaluated result s IRU ³pass ´
and ³re fer ´ OAE rates an d t ymp anometr y amon g t he po pulation are shown in Table 4.6 and Fi g.
4.3 respecti vel y.
Table 4.6: Evalu ated OAE passes/ ref errals an d typ es of mid d le ear disord ers
Test v ariab le Frequency
(a/b)
Percent age
a/b
OAE Test Pass 123/121 51.5/50.8
Refer 115/116 48.1/48.7
Total 100
Tympanomet r y Test A 358/354 73.4/72.5
A s 16/13 3.3/2.7
A D 5/8 1.0/1.6
B 72/67 14.8/13.7
C 37/46 7.6/9.4
Total 100
Legend : a/b si gnifies ri ght ear/l eft e ar
University of Ghana http://ugspace.ug.edu.gh
4 0
Fig. 4.3: Tympan o met r y in lef t and righ t ears
Over half (51.5 %/50.8% ) of the pati ents under going OAE test passed while 48.1%/48.7% of
them ref err ed. An al yz ed data from the t ymp ano gr ams showed that 73.4 %/72.5% , 3.3%/2.7% ,
and 1.0%/1.6% of them were classified as Typ e A, T yp e A s , and Type A D r especti vel y.
Comparati vel y, fewer pati ents wer e cate goriz e d int o T ype B (14.8% /13.7% ) and T ype C
(7.6%/9.4%).
A discussi on of the result s is presented in Chapter Five whe re comparis ons with the literature
and other publi shed mate rials are mad e.
0
50
10 0
15 0
20 0
25 0
30 0
35 0
40 0
A A S A D B C
Fr
e
q
u
en
cy
Types of tympanograms in left and right ears
Le ft ear
Right ear
University of Ghana http://ugspace.ug.edu.gh
4 1
CHAPTER FIVE
DISCUSSION
5.1 INTRODUCTION
In thi s Chapter, the res ult s obtained from th e s tud y are discussed. Co mparisons ar e weigh ed
against the literature and other publi shed to asce rtain the vera cit y and accu rac y of th e result s.
5. 2 DEMOGRAPHIC PATTERN OF HEARING LOSS
Age and gend er demo gr a phics were consi dered in stud yin g the preval ence of hearin g loss at the
defined stud y sit e.
5. 2.1 Gender Distrib u tion of Hearin g Loss
A tot al number of 715 pati ents reported to the Hearin g Assessm ent Cente r of KBTH for hearin g
screenin g between the periods of Januar y 2012 - Decemb er 2012. Ov er 66.3% ( n=475) of the
sampl e population presented with hearing loss . The male population accounted fo r 51.9%
( n=372) of th e number whil e the lower fracti on of 48.1% ( n=344) wer e females. Although mor e
males visi t ed the Cent er, the prev alenc e of hea rin g loss in one or both ears was hi gher in females
than in males. In particul ar, 160 fem ales ha d he ar ing loss in the right ea r and 168 in the left ea r
compared to 146 and 147 for the male population. This result is consi stent and in agr eement with
the findings of Amedo fu et al (2005 ) which esta bli shed in an evalu ated s tud y of 6,426 pati ents
that there were mor e hea r ing impaired wom en tha n men.
It is how ever contrar y to the findings detailed b y Cruikshanks et al , (1998) , Wil son et al (2010),
Marfo (2009) and NAAS (1999) that men of all ages are mor e likel y than women to have
University of Ghana http://ugspace.ug.edu.gh
4 2
hearin g loss . As noted by Ake em et al (2010), there have be en inconsist encies in various studi es
cit ing gende r as a risk factor for he arin g loss : some have found fem ales to be at a higher risk,
while others found th e contrar y as th e case. Th e result s of thi s stud y th e refor e consi stent with
and thus confi rms the ob served variati on or contr adictions of gend er relate d hearin g loss report ed
in the literature.
5. 2.2 Age Distrib u tion of Hearin g Loss
Out of 715 pati ent s who reported to the C ent er for hearin g loss and as sh own in Table 4.2 , the
most prevalent group of pati ents presenti ng wit h hearin g loss where ch il dren (35.9%, n=256 )
below 9 yea rs of age, while the prevalence of adu lt s aged 50 -59 ye ars, and above 60 years were
11.1% ( n=79 ) and 8.4 % ( n=60 ) resp ecti vel y. Pati ents with no recor ded age demo gr aphics
accounted for 5.2% ( n= 3 8 ) of the populati on.
From Table 4.3, a low er fra cti on (33.7%, n=2 41) of pati ents had nor mal hearin g . On the
contrar y, a relativel y lar ge r group ( 66.3%, n =4 74) wer e dia gnosed with hearin g loss , with the
most prevalent being pati ents aged 60 and above with hearing loss for both left and right ea rs
was recorded for pati ents (88/92: conducti ve=4/3; sensorineur al= 52/54; mix ed =32/35). The 0- 9
ye a rs group show ed t he least prev alence (15/12: conducti ve=9/6; sensorineur al=24/24;
mix ed=14/15).
The findi n gs of this stud y cl earl y sho w that p r eva lence of hearin g loss incr eased with age . This is
consi stent with the litera ture (Mitche ll et al, 2011 ) and in line with Ma UIR¶V ZRUN on the
prevalen ce of hearin g impairment in the Offinso Muni cipalit y of Ghan a which reveale d found a
44% prevalen ce of hea ri ng loss among adult s age d over 60 yea rs. The find ings of thi s stud y also
University of Ghana http://ugspace.ug.edu.gh
4 3
agree wit h the work of Cruikshanks et al., (1998) which reported that prev alence and sev erit y of
hearin g loss incr eased wit h age, risin g from abou t 30 -35% of adult s aged 65 years and old er to
an esti mated 40-50% of adult s aged 75 and older , and is also consi stent with other studi es (Le e
et al,, 2005; Curhan et al., 2010) that t he pr eva lence of hea ring loss increas es with age , with
hearin g thr eshol ds worse n ing on aver a ge b y 1 dB per year afte r age 60 years, and decli ne rate s
gr eate r in men aged 48-5 9 ye ars. Other liter ature (Helz ner et al, 2005; Bo rc hgr evink et al, (2005)
have be en publi shed to confirm the result s of high pr evalen ce of h ea r ing loss amon g older
persons and des cribed th e gradual o r non-li nea r dependen ce of the prev ale nce with age.
5.3 TYPES OF HEARING IMPAIRMENT AMONG THE STUDY POPULATION
The various t ypes o f hear ing impairm ent we re eva luated for both the ri ght and left ear sepa ratel y.
The over all data gather ed suggested that, SNH L was the most comm on fo r both the left and ri ght
ear , with pr evalen ce rates of 36.7% and 40.5% in t he right and left ears resp ecti vel y.
Th is finding that SNH L i s the most prevalent t ype of hearin g loss is consi stent with Amedofu et
al (2005) ev aluated wo rk on 6,426 pati ents in Ghana, and further emphasi z ed in various studi es
(Salvago et al, 2013).
5.4 UNILATERAL VERSUS BILATERAL HEARING LOSS
Out of the 474 pati ents who had hearin g loss , 23 .3% pres ented with unil a teral he arin g loss . The
dist ributi on of the unil ateral hea rin g loss was 13.6% for ri ght ear and 17.7% for left ea r. About
68.7% pres ented with bil ateral hearin g loss . The fact that hearin g loss tends to be a bilater al
condit ion is also support ed in a stud y b y Abdel - Hami d et al (2007 ). The stud y found out that,
University of Ghana http://ugspace.ug.edu.gh
4 4
bil ateral hearin g loss was present in less than 7 6 % of the population with hearin g loss a while
unil ateral hea ring loss was present in ove r 24%.
5. 5 AUDIOMETRIC CONFIGURATION OF HEARING LOSS
The most prevale nt eval uated audiom etric confi gur ati on of hearin g loss was mild hearin g loss
(45.9%/16.1 %) for both right and left ear (Tab le 4.5). The result agre es with the publi shed
findings of b y Amedofu et al (2005) and Mar fo (2009) which rep mild he aring loss as the most
prevalent audiom et ric co nfigur ati on of hea rin g loss .
The rev erse slope was the least pr evalent for both right and left ears evaluated. Th er e was
35.4%/33.6% normal con figur ati on of hea rin g loss for bo th ri ght and left ea rs respe cti vel y.
5.6 OTOACOUSTIC EMISSIONS
From Tabl e 4.6, 51.5%/ 50.8% of the popul ati on passed OA E test while 48.1%/48.7% refer red
for the ri ght and l eft ea r resp ecti vel y. Majo rit y of those who unde rwe nt the OAE test were
chil dren from 0-9 ye ars. The high refer ral rate esti mated in thi s stud y is co nsis tent with the stud y
conducted b y Abdel -H a mi d et al (2007) where 16.2% of OAE fail ures ac tuall y present ed with a
type of hea ring loss .
5.7 TYMPANOMETRY
Majorit y of the pati ents record ed a normal t ymp anogram . From Fi g. 4.3, the Type A cl assi fied
t ympano gr am was mos t preval ent (73.4%/72. 5%). Comparati vel y, fewe r pati ents were
cate goriz ed int o T ype B (14.8%/13.7 %) and Typ e C (7.6%/9.4%) while Typ e A D was least
(1.0%/1.6%) pr evalent.
University of Ghana http://ugspace.ug.edu.gh
4 5
Th e result s of the stud y ar e suggesti ve that among pati ents wh o recorded abnorma l
t ympano gr ams, majorit y had a T ype B confi gura ti on indi cati ng pres ence of fluid in the middle
ear. This findin g is signi ficant bec ause the majo rit y of the pati ents who ca me visi ted the Center
also suffered a typ e of hearing loss . Gener all y, middle ear problems includi ng oti ti s media
contribut es lar gel y to hea ring impairm ent . The obs ervati on of the presenc e of thi s problem in thi s
stud y is emphasiz ed in detailed in a prospe cti ve cross -s ecti onal stud y on 51 pati ents at KAT H
conducted b y Awuah et al, (2012) where he arin g loss occurred in majorit y of pati ents sufferin g
acute otit is media.
University of Ghana http://ugspace.ug.edu.gh
4 6
CHAPTER SIX
CONCLUSION AND RECOMMENDATIONS
6.1 INTRODUCTION
The summ ar y of the res earch findings, con clusi on and recomm endati on s are pres ented in thi s
Chapter.
6.2 CONCLUSION
Th is stud y was condu ct ed to ev aluate the prev alence of hearin g loss at KBT H. Th e result s
reveal ed that out of the total number of 715 pati ents who visited the Hearing Assessm ent Center
during the speci fied pe riod of the stud y, 66.3 % ( n=474 ) pres ented wit h different t ypes of
significant h earin g loss of which SNH L was mos t prevalent with rates of 36 .7% and 40.5% in the
right and le ft ea rs resp ect ivel y. This prev alenc e of 66.3% is alarming.
The result s fu rther reve a led that alt hough more males report ed to the cli nic than fem ales, the
prevalen ce of hea ring lo ss was higher in females than males. This find is consi stent with some
studi es and contra r y to others as ex pected from the contrasti n g literatur e . Chil dren below nine
ye a rs most frequ ented t he Center, but had th e least prev alenc e of hea r ing loss . Th e hi ghest
p revalen ce of hearin g los s among the age groups was reco rded fo r those who are abov e 60 years
and was followed b y th e cate go r y above 50 ye ars. This finding was however consi stent with
publi shed literature. In addit ion, mild configurati on of hearin g loss wa s determi ned as the most
prevalent audiom etric co nfigur ed hearin g loss . As ex pected t he le ast co nfigur ati on const it uted
University of Ghana http://ugspace.ug.edu.gh
4 7
the reverse slope cate gor y. Bil ate ral hea ring loss was more prevalent than unil ateral hearin g loss .
Relativel y mor e pati ents passed the OAE t est tha n fail ed . Th e most and l east pr evalent t ypes of
t ympanometr y w er e T yp e A and A D respe cti vel y.
Hearin g loss is a frequen t sensor y dis abil it y af fect ing pe rsons of all ages and gend er. T h e result s
of thi s stud y demons tr ate that hearing loss is a ver y comm on problem af fec ti ng older adult s . This
information is ver y imp ortant and presents a po tential contribut ion for effecti ve plannin g and
resourc e investm ent in audit or y rehabil it ati on services in Gh ana. A co uple of strate gies have
been advo cated fo r miti gati n g the disabil it y. In particular, Cruicksh an ks et al (1998) have
proposed the need for ep idemiol ogic studi e s to understand the geneti c, environmental and
gend er- related determi na nts o f age- relat ed heari ng loss and to identif y p otenti al int erventi on
strate gies. Hede rstierna et al, (2007) have also suggested that hormone replacement ther ap y
(HRT) ma y pr esent the capabil it y to offer a protecti ve effe ct on hearin g impa irment in
post menopausal women, as well as new guidelines for classific ati on of audi ometric confi gur ati on
in age-r elated he arin g los s .
6.3 RECOMMENDATIONS
Based on th e outcomes o f th is stud y, the foll owin g recom m endati ons are s uggested:
Th e result s ar e ver y imp ortant and pres ents a potential contribut ion for eff ecti ve plannin g
and resour ce investm ent in auditor y rehabil it ati on services in Gh ana
The result s of the stud y clearl y id enti f y the need for ex tensive pati ent hist or y records for
purposes of ev aluat ing ca uses of hea ring impairm e nt .
University of Ghana http://ugspace.ug.edu.gh
4 8
Nati onal surve ys on the prevale n ce of hearin g impairment shoul d be conducted to assess
the nati onal impact of hearing loss . This can be done by using the WHO protocols set out
to guide indivi dual count ries to conduct prev alenc e studi es.
The economi c impa ct of hearin g loss on the econo m y must be assess ed .
S ince there ar e conflicti ng result s on the prevale nce of hearin g impairme nt among men
and women, a stud y to determi ne wh y there are more women with hear ing loss than
women shoul d be conduc ted.
The Minist r y of Healt h shoul d consi der ex pandi ng the Hearin g Ass essm ent Center of
KBTH and provide ne cessar y equipm ent sinc e there is a large bur den of hearin g
impairment and most of these pati ents will need fu rther ev aluation and assi s tance.
S atelli te offices shoul d be set up in order to assi st with the hearin g ne eds of pati ents in
outl yin g areas.
Since the stud y establi shed that the majorit y of hearin g loss es are permanent an d
sensorineural in nature, funding for hearin g aids and rehabil it ati on servi ces shoul d be
consi dered.
Attention should be given to the elderl y pati en ts since the y were foun d to have the
highest preval ence of hea ring loss . An aural reh abi li tation cli nic shoul d be set up to assi st
the elderl y.
The Minist r y of Healt h must support the earl y i denti ficati on pro gr am th at has alread y
started at the KBTH an d provide mor e OAE and ABR ma chines to enable the conti nuit y
of the pro gram.
More audiol o gist s must be trained to help s erve the needs of indi viduals who might be
sufferin g from hea ring i mpairment and thos e wh o alread y have one.
University of Ghana http://ugspace.ug.edu.gh
4 9
REFERENCES
Abdel -Hami d, O., Khati b, O.M.N., Al y, A., M orad, M., Kamel, S. (2007). Prevalenc e and
patt erns of hearin g i mpairment in Eg ypt : a nati onal househol d surve y . Eastern
Mediterranean Health Journal . 13 (5 ).
Access Economi cs (200 6). List en, Hear! The economi c impact and co st of h ea ring loss in
Australi a. (htt p:/ www.ac cesseconomi cs. com.au/p ubli cati onsreports/s howr eport.php? id=71)
Agraw al , Y. , Platz , E. A., Niparko, J . K. (2004). Prevalenc e of hea ring lo ss and differen ces b y
demogr aphic char acte risti cs among US adult s: data from the Nati onal Heal th and Nutriti on
Ex ami nati on Surve y, 199 9 -2004.
Akeeem, O. L., Taiwo, A. , Oye, G. (2010 ). The pre valence and corr elates of self -report ed hearin g
impairment in the Ib ada n stud y of agein g. Tran sacti on of th e Ro yal So ciet y of Tropical
Medicine and H ygien e. 104(8): 518 -523.
Al Khabori, M. , and Kha ndekar, R. (2007).Unilat eral hea rin g impairment in Oman. Ear Nose and
Throat Journal, 86(5): 274, 277 -80 .
Atti as, J ., Al-Masri, M., Abukade r, L., Cohen, G., Merlov, P ., Pratt , H., Othman -J ebara, R.,
Abere, P, Raad, F., No ye k, A. (2006). The prevale nce of con genit al and ear l y-onset he arin g
loss in Jordanian and Isr a eli infants. International Journal of Audiology , 45 (9 ): 528 -536
Amedofu, G.K., (2007 ). Effecti ven ess of hearin g co nservati on pro gram at a lar ge sur fac e gold
mining compan y in Ghan a. Afric an Journal of Health Sciences , 14 (1 -2 ): 4 9 -53.
Amedofu, G.K., (2002) : Hearing - Impairment Among Workers in a Surface Gold Mining
Compan y in Ghan a. Afr ican Journal of Health Science, 9:91 -97.
Amedofu G.K., Brobb y G.W ., Ocanse y, G. (1 997).The caus es and pr evalenc e of pre -school
deafness in Gh ana. African Journal of Health Science , 4 (1 ):29 -32.
University of Ghana http://ugspace.ug.edu.gh
5 0
Amedofu, G.K., Ocanse y, G. Antwi, B. (2006 ). C haracte risti cs of hearin g impairme nt amon g
p ati ents in Ghana. Africa Journal of Health Science , 13(1-2):110 -6 .
Amedofu, G.K, Opoku - Buaben g, Osei - Ba g yina, A. et al., (2003).Hea ring loss among s chool
chil dren in Ghana. Ghana Medical Journal , 37, 148 -152 .
American Spe ech and Hearin g Asso ciation (AS HA) (2008). T ypes of hea ring loss .
htt p:/ /www.asha.or g/publ ic/hearin g/di sorders/t ype s.ht m. Accessed 18 th J an. 2013.
Awuah, P., Duah, I.M., Amedofu, G.K. Prev alen ce of hearin g loss in pati ents with acute oti ti s
media . Journal of Science and Technology (Ghana). ISSN: 0855 -0395.
Ba gule y, D. M. , Bird , J . , Humphriss , R. L. , Prevost , A. T. (2006 ). The evidence base for the
appli cati on of contralate r al bone anchor ed he arin g aids in acquired unil at er al sensorineu ral
hearin g loss in adults . Clinical Otolaryngology ; 31(1): 6-14.
Boat en g, C.A, Amedofu, G.K., (2004). Indust rial noise poll uti on and its effe cts on the hearin g
capabil it ies of wo rkers: A stud y from saw mill s, print ing pr esses and cor n mill s. African
Journal of Health Science. 11 (1 -2):55 -60.
Borch grevink , H. M. , Tambs , K. , Hof fman , H. J . (2005). The Nord -Trøndel a g Nor wa y
audiom etric surve y 1996 -98: unscreen ed threshol ds and prevalen ce of hea ring impairment
for adult s >20 ye ars. Noise Health . 7(28):1-15.
Cruickshanks, K. J., Wile y, T. L., Tweed, T. S., Klein, B. E. K., Klein, R., Mares -P erlman, J . A.,
et al. (1998). Prev alenc e of hearin g loss in older adult s in Beave r Dam, Wisconsin. The
Epidemi olog y of Hearin g Loss Stud y. American Journal of Epidemiology , 148, 879 ±886 .
Curhan, S.G., Eav e y, R., Shar gorodsk y, J ., Curh an, G.C. (2010). Anal ge sic use and the risk of
h earin g loss in m en The American Journal of Medicine, 2010; 12(123); , 23 1 -237
University of Ghana http://ugspace.ug.edu.gh
5 1
Fowler, C. G., & Shank s, J . E. (2002).T ymp ano metr y. In J. Katz (Ed.), Handbook of cli nical
audiol og y (5 t h Ed. ). Bal ti more: Lippi ncott Wil li ams & W il kins .
Fria, T. J . , Cantekin , E. I. , Eichler, J . A. (1985). Hearing acuit y of chil dr en with effusion . Archives
of Otolaryngology . 11:10 ±16. PubMed .
Gelfand, S.A. ( 2009 ). Essentials of Audiol og y. ( 3 rd Ed. ) New York: Thie me Medical Publi shers,
In c.
Gordis, L. (2000). Epide mi ology. (5 t h Ed . )P ens yl vania: W.B Saunders Co mpan y.
Ha yes, D. , Northe rn, J . (1996). In fants and Hearing. San Di e go, Cali f .: Singular Publi shing
Group, Inc.
Hederstiern a, C., Hultcr antz , M., Colli ns, A., Rosenhall , U. (2007). Hearin g in women at
menopause. Preval ence of hearin g loss , audiom e tr ic confi gurati on and relat ion to hormone
replac ement therap y. Acta Oto-laryngologica , 127(2), 149-155
Helz ner, E. P . , Caule y, J . A. , Pratt , S. R . , et al. (2005). Race and sex differenc es in age - related
hearin g loss : The Healt h, Agin g and Bod y C ompos it ion Stud y. J Am Geriatr Soc .
53(12):2119-2127.
Katz , J . (2002). Cli nical audiol ogy. (5 t h Ed). Mar yl and: Libr ar y of congr ess catalo guin g - i n -
publi shing data.
Kitcher, E. D. , Ocans e y, G. , Tumpi , D.A. (2012): Earl y occup ati onal hea ring loss of work ers in a
stone crushin g indus tr y: Our ex perienc e in a dev e lopi ng countr y. Noise Health. 14:68 -71.
La For ge, R. G. , Spector , W. D. , Sternber g, J . (1992 ). The rel ati onshi p of visi on and hea rin g
impairment to one- yea r mortali t y and fun cti onal decli ne. Journal of Aging and Health
4(1):126 -148.
University of Ghana http://ugspace.ug.edu.gh
5 2
Le e, F. S . , Matthews , L. J . , Dubno, J . R . , Mills , .J . H. (2005). Lon git udinal stud y of pu re-ton e
threshol ds in older perso ns. Ear Hear .26:1 -11
Mar goli s, R. H., Hunter, L. L. (2000). Acoust ic I mm it tance Measureme nt s. In R. J. Roeser, M.
Valente & H. Hosfo rd- Dunn (Ed.), Audiolo g y Diagnosi s. New York: Thieme Medical
Publi sh ers, Inc.
Marfo, A . (2009 ) . Prev alence of hearin g impair ment at Offinso Muni ci pali t y. Dissert ati on for
the de gre e of MSc. Kw a me Nkrumah Unive rsit y of Science and Technolog y.
Mathers, C. , Smi th , A., Concha M, (2013). Glo bal burden of hearin g Loss in the yea r 2000 .
Retrieved onli ne from www.who.int /healt hinf o/st ati sti cs/bod _hearingl oss.pdf , acc essed
18 t h Januar y, 2013) .
McPherson, B., Holboro w, C.A. (1985). A study of dea fness in West Africa: Th e Gambi an
hearin g he alt h project . International Journal of Pediatric and Otorhinolaryngology , 10 (2):
115 -135.
Mehra, S, Eave y R.D an d Keam y D. G. (2009 ). The epidemiol o g y of hear ing impairment in the
United States: newborns, chil dren, and adolesce nts. Otolaryngology Head Neck Surgery,
140:461 ±472. PubMed
Mitchell , P., Gopinath , B . , Wan g, J . J . , McMahon , C. M . , Schneider, J . , Rochtchina, E . , Le eder
SR (2011). Five- ye a r i ncidence and pro gr essi on of hearin g impairm ent in an older
population Ear Hear . 32( 2):251 -7
Moller, A.R. (2006). Hea ring: An atom y, ph ysiol o g y and disorders of the audit or y s ystem. 2 n d Ed.
Amst erdam: Acad emi c press.
University of Ghana http://ugspace.ug.edu.gh
5 3
Mul row, C. D., Aguil ar, C., Endicott , J . E., Tule y, M. R. , Velez , R., Charlip, W. S., DeNino, L.
A. (1990). Qu ali t y- o f -li f e chan ges and hea ring i mpairment. A randomi z ed trial. Annals of
Internal Medicine, 113, 188 ±194. (Retrieved from
http:/ /www.asha.or g/Aud /Articles/Untreated -He ari ng- Loss - i n -Adults )
Nati onal Ac adem y on An Aging Societ y (1992 ). Chronic Condit ions: A chall en ge for th e 21st
centur y No. 2
Northern, J . , Downs M. Hearin g in Chil dren (1991) . 4th Ed. Balt im ore, Md: Will iams and
Wil kins.
Onusko, E. (2004). T ym panometr y. American Family Physician , 70 (9 ), 1713 ± 1720.
Oyle r, R.F., Oyl er A. L and Matkin, N.D. (1988). Unilateral hearin g l oss -d emographics and
educati onal impact . Language, Speech, and Hearing Services in Schools Vol.19 201 -210.
Ruben R. - ³5edeIining tKe VXUYiYaO RI tKe IitteVt comm unicati on disorders in the 21 st
FentXU\´ The Laryngoscope 110:241 -245 .
Salvago, P ., Marti nes, E ., Marti nes, F . (2013). P revalence and risk factors for sensorineur al
hearin g loss : Western Sicil y overvie w. Eur Arch Otorhinolaryngol . 270(12):3049 -56
Saunders, J .E., Vaz , S., Greinwald, J . H., Lai, J ., Morin, L., Mojica, K. (2007). Prevalen ce and
eti olog y of hearin g loss in rural Nic ara gu an chil dr en. Laryngoscope, 117(3 ):387 -98.
Se el y, D.R., Glo yd , S.S ., Wright , A.D., Norton S.J . (1995) . Archives of Otolar yn golog y. Head
and Neck Surgery, 121 (8): 853 -8.
Stol l, L., Fink, D. (199 6). Changin g our s choo ls: Linki n g school effe cti veness and school
improvement. Open Uni versit y Pr ess, Buckin gh a m, U.K.
Veras , R. P . , Mattos , L. C . (2007). Audiolog y and agin g: literature review and curr ent
horiz ons . Brazilian Journal of Otorhinolaryngoly , 73(1):122 -8 .
University of Ghana http://ugspace.ug.edu.gh
5 4
W il e y, T. L., and Fowler , C.G. (1997). Acoust ic i mm it tance measures i n cli nical audiol og y: A
prim er. San Die go: Singu lar Publi shing Group, In c .
Wil son, R.H., Noe, C.M., Cruickshanks, K.J ., Wil e y, T. L., Nond ahl, D. M. (2010). Prevalen ce
and de gre e of hearin g loss among males in Beav er Dam coho rt: Comparison of vetera ns
and no nveter ans . Journal of Rehabilitation Research & Development . 47(6) , 505 -520
World Healt h Organiz ati on (2012), De af and Hea ring impairment, Genev a (Retrieved onli ne
http:/ /www.who.int/ mediacentr e/fa ctsheets/ fs300/ en/i ndex .htm l
Yoshinaga- Ita no , C. , Sede y, A. L. , Coult er , D. K. and Mehl, A. L. (1998). Langu a ge of earl y- and
later-identified chil dren with hearin g loss . Pediatrics ,102(5):1161 -71.
University of Ghana http://ugspace.ug.edu.gh
5 5
APPENDIX I
University of Ghana http://ugspace.ug.edu.gh
5 6
APPENDIX II: PERMISSION TO CARRY OUT RESEARCH AT STUDY SITE
University of Ghana http://ugspace.ug.edu.gh
5 7
APPENDIX III: EHICAL CLEARANCE
University of Ghana http://ugspace.ug.edu.gh
5 8
University of Ghana http://ugspace.ug.edu.gh