prevelensi retardasi mental.pdf

8/11/2019 prevelensi retardasi mental.pdf

1/8

The prevalence of

mental retardation:

a

critical review

of

recent literature

Mental retardation AIR) is a serious and lifelong disability

th at places heavy demands

on

society and the health system.

Since the first publication on this topic' , theprevalenceofMR

has been thoroughly studied for different purposes. Most

prevalence studies are designed for th e planning of services

and establish an 'ascertained' prevalence rate, which is the

number of cases officially recorded by the authorities'.The

'true'prevalence rate

is

th e total number of mentally reta rd-

ed people in

a

population, whether

or

not they require ser-

vices,and isdefined by th e prevalence ofM R t birth and the

mortali ty rate.For mild mental retardation

(MWR, I&

50-70)

the t ru e prevalence rate is more difficult to estimate than

for

severe mental retardat ion (SMR,

IQ


2/8

Table I Continued

Re/ .41tfhorrr td h r

C'owntr y

.Il~fltotlr,/cttse V i l i d i t y

Rrlrci S i z e 14

A g p S.lIIt

.11.lIlt

. yet trof

of

#

n i d

i sw r t u i i i t i i e n t

(+,

good: it orittdiott

nlud y ( yeor+-)

p i p e r

prtblicrtliott

. d i t dy

. s p ~ c ~ c c ~ l i o ~ r --, w o r ) p o p t

la

io 1

1000

1000

23

Brask

(197'2) 1963

Denmark. Xational register

SMR? 35183 5-14 3.3

Aarhus county BIBIR- (aaccrtained

A N R 3.2)* .

24

Akesson

(196i)

1964

SnP den.isla ntls: 1.c1cal register SJ IR + SBlR

IQ


3/8

ed. population surveys);4) the clinical and/or psychometric

research performed to classify cases into grades of

AIR ( i n

accordance with I & level).

For

SMR,

register-based case ascertainment follo\vcd by

the re-evaluation of IQ levels was considered sufficient to

render reliable figures for the p re ~a le nc e. ~s most registers

are virtually complete for

SMR,

the ascertained prevalcnce

rates can be interpreted as estimates of the true prevalence

rate.The precision of the prevalence estimates is expressed

by the

95%

confidence intervals (C1) in Figure I .The average

SMR

prevalence rate \nus calculated by using the inverse

variance of the rates as a weighting factor.

The prevalence rates of &IMRare judged t o be valid only

i n

studies in \vhieh register-based case ascertainment was

supplemented with additional research,or a population sur-

vey was performed, including extended psychometric and

diagnostic evaluationn. n three s tudies,only the overall

AIR

prevalence rates were given, but the rates for blMR were cal-

culated by substracting the average Shl

R

prevaleiicc

rate's.'H. '. The ascertained prevalence rates of AIAIR were

considered to be underes timates

of

the tr ue prevalence rate.

These rates were therefore not included

i n

the calculation of

the average MMR prevalence rate and are presented sepa-

rately in Figure 3.

Concerning the quali ty of the material, several autho rs

stated that i t

is

difficult to find two single studies tha t are

comparable in meth~dology~~'~~~' ' .he selection criteria

described above increased the comparability of the stud ies

considerably but differences still remained (Table I ) , for

studies the method of case ascertainment was definitely

more thorough th an in ~tliers' ' ~'~.~'. ~.~~'.As the ascertain-

ment of cases

is

best in children of school age up t o

19

years

old, he age range was confined t o ages

5

to 19,on the basis of

recalculation of the prevalence rates from

14

studies \vhile

instance n

t h e upper l Q l i m i t s ' . ~ ' ~ ~ ~ . ~ ' . ~ i . ~ . ~ . ' H . ~ ' I n some

prevalence rate / 1000' (95 CI)

10

omitting the age-specifie rates for

the

youngest and older

agegroups.Asubstantia1variation in age range was Ieft.ho\v- .

cver.Table I also

shows

R huge variation

i n

population size,

\vhich is reflected

i n

the

95%

confitlence intervals of the

prevalence rates

i n

Figures 1 and 3.

Prevalence

of

SMR

.As shown i n Figure

1

, theprevalence ra te for SMR in children

of school age

is

relatively stable, varying around an average

value of 3.8 per 1000.This agrees well w i t h the SMR preva-

lence rates mentioned

i h

studies conducted before 1960 and

with t he WHO.which considers

a

rate of 3 to 4 er 1000 to be

a good estimate of the true

SAIR

prevalence rate i n Western

countries9

7.

Nrtrkcdly higher rates were observed i n only

five studies. owing to a better method of case ascertain-

ment' '6.'5.4 I..X

Comprehensive reviews have been written by Fryers antl

Dupont'J on the dynamics of the prevalence of hI R, evealing

patterns

of

temporal change. I n Figure

1

no time trend is

observed for SMR,but Figure 2 clearly shows that t he preva-

lence rate for

SRlR

is age dependent.Thc age-specific rates

show an increasing prevalence u p to the age of 15.whicli indi-

cates that ShIR

is

not fully asscwed in the first few years of

life.This is a reflection of the way i n which developmentally

disabled children become known to service providers and

can be traced through schools5 .103 i The decreasing

prevalence rates i it l ie older age groups can be explained by

a higher than average mortality among the severely mentally

retarded and

by

flaws

n

registers antl research methods.

Gender-specific ratcs were presented

i n

approximately

half of the studies. For

SMR

the malc-to-female ratio is

remarkably constant antl indicates a 20% excess of males,

probably due t o sex-linked genetic factors . Obvious geo-

graphical differences were not observed. Only a few studies

mentioned higher rates i n rural compared with urban

areas.

1

I

Figure 1:Precaleace ofSJIR in children ofschool aye (ch ronological order

1960-87).

Annotations

1 2 i

< 'A-


4/8

These differences

we&

explained by a higher maternal age in

th e country, selective m igt'ation. religious affiliation, a high

degree of endogamy,endemic meningitis and poor ant ena tal,

per ina ta l and pos tnatal ca re24~t4~R G~M ~5D.

Apparent ly there

is

l i t t le variation between populations

concerning th e prevalence of SMR .This indicates tha t t he

aetiological process of ShIR is not influenced greatly by

exogenous factors.

Prevalence of

MlKR

Th e prevalence figures for JIM R exceed th ose for th e severe-

ly retarded and th e variation in rates

is

enormous (Figure 3) .

I t is not clear wh ether this is a reflection of th e non-com pa-

rabi l ity ofstudies o r of real differences between po pula tions .

The identification of cascs is virtually complete

i n

t h e lo\ver

IQ

ranges, but as long as children wi th an

IQ

of less t h an 70

are able to cope w ith the school system they

will

not become

known to the authori t ies . Although th e ident i f icat ion of

prevalence rate

/

1OOO

6

5

4

3

2

1

0

0-4 5-9 10-14 1519 20-29 30-39 40-49 50-59 60+

age in

5-

or

10-

year intervals ;

Figure 2:Age-specificprevalence

rates

of SMR:@, Goodman and Tizard'";+,Kushlick"; *,Sca lly andi1IarKay";C l. Brask":

X.

Hbllin'"-Q .i)-lacKay'";A,G o d d " : O , Bermen".

prevalence rate

/ 1OOO (95% C1)

100

80

60

40

20

0

20 21

23

25 26

28 31 37 38

42

43 45

50

51

55

referenc es of stu dies Listed in Tabte I

Fi-

3:

revalence of MMR in chi ldren of school age (chron ological order

1962-87).

128 Decelvpniental Nedir ine C'hildiVeVe,irology 997,39: 125-382


5/8

- .

B I M K is most pronounced at sclioql agei.8.1ti,complete

assessment cannot be achirved before maturity. Therefore

register-based case ascertainment, particularly in the

younger agc groups. leads to a gross underestimation of the

true N h I R prevalence rate.

This was clearly shown

in

five studies i n which true and

ascertained prevalence rates were co~ni)aI~d~O.:j l .~ i .~l . '~ .s

the rates presented by Sore126,Hagberg et al.43,Kaariainen15

and Rantakal lio and von \Vendt have not been assessed by

population surveys and fall into the range of ascertained

prevalence rates,

it

is vcry likely tha t these rates under-esti-

mate the true

M J I R

prevalence rate as well. However, these

lo~wrates might also reflect th e influences of improved cnvi-

ronments ant1 increased mean 1Qs in those

po~~ulatio~is~"~'~~-'"'.n contrast, Lemkau and ImreZRnd Stein

et al.:li found extraordinarily high JIAIR prevalence rates in

profound screening of the population wi th individual IQ

tests.Over-reporting could be t h e case here.The former study

was conducted in a low socioeconomic area, with little stimu-

lation to perform well in I & testing. In Stein's study on 19-

year-old males it isnot unlikely tha t some tried to be labelled

mentally retarded

( I &


6/8

countries

is

mow complex

t h a n i n

th e \\restern world.

Registers

ere

not available

or

are extremely incomplete, and

pojidation surveys also pose a lo t of problems.

I n

cities the

mobility of the population

is

usually high and

many

lan-

guages are spoken. Rural communities are often charac-

terised by

a

large proportion of illiterate inhabitants. the

non-existenceof

bir th

registers an d a lack of cooperation .

In these less demanding communities a large percentage of

AIAlR

may go unrecognisetl. However, th e use of

IQ

tests can

lead t o extremely high prevalence estimates because the te sts

arc

often far from adeqiiate for non-\\restern populatioqd . .

This can resiilt

in

underestimation

or

overestimation df the

tr ue pivvalence rates for

A 1 R.

I n

Figure

4

he

SMR

prevalence rates

( Q 55or

less)

from

population surveys

in

eight. developing count ries ar e present -

cti .The rates for children 3 to Oyearso l d h

rural

c6mmuni-

ties wit11 approximately

1000

inliabitants, varied between

5

antl 16 per

1OOO.

with t he exception of India , where

a

rate of

40

per

1000

was found. Sarayanant ii and asan

a nd

Hasan '.

reported similarSAIR

prevalencerates.Thqrefore

he average

prevalence rate forSAIR t i developing countrie s

was

calcnlat-

ed to be

9.3

per 1000.\diich is

2.5

times hidher tha n t he aver-

iige

rate in Western countxies.This rate might be artificially

elevated

or it

might be explained by a hi$her prevalence of

SJlR

a t bir th or postnatally

due

to, for ipstance, malnntri-

t

ion.ronsanguinity,infections

n c ~natleq+te perinatal care.

The

AXAID'

and the

\ \ 'H09

sugges ted th at a high prevalence

rate a t birth will be counterbalancedby

a

rhatively high mor-

tality among mentally retarded children, resulting

i n SBIR

prevalence rates similar t o those i n the \\e@,ern world.

On

the

available evidence th is does not seem to

be So.

Stein et al.i''also reported prevalence rates for

ICIAIR

from

the eight commuiiity surveys. which

ranged

from 4 pel:

lo00

in

the Philippines to

138

per

1000

i n Bangladesh. Hasa n

and

Ha sai P found an

AIAIR

prevalence rate

of

28

per

1000

for

children aged 0 to 10

years

in Pakistan and92 per 1000for 11

to20-year-oltls.

I n an

Indian sir vey an ove 'all

AIR

prevalence

rate ( I Q


7/8

17. Jlc1,aren

J.

Brywn SE.( 987)He *irwof re cent epitleniiologiral

studies of m ental retarttat ion: prc]Talence,associateti disoniers,

and etio1ogy.d ni er~ cu t~ortr?ia/

of.llrntnl

Hrtnrdfition

92:243-54.

18.Goodman Xlizard ,J.(

1962)

Prevalence of imbecility

and

idiocy

amo ng cliildren.Brilidi .1terlical Jour na l 1:2 16-9.

19.KiislilickA.( 1961) Siibiiorniality in Salford . 1n:Susser>I\\:

liuslilickA,etlitors.rl Report on /heillenla/ Heallli Seraices oJlhe

Ci ly ofSnonlJordfor the J ia r 1 060.S alfor~I :SalfortlHealth

Depar tn icnt .p 1 1 8 4 8 .

Jlenf nl Si i lnortnnl i / /

n

the

Cwnni

r i i i i / y . i l

Cliniral

a n d

Epi drni ioloyic Strcdy. Baltiiiiore:\\illiams 8: \\ilkins.

21. Ihillicn (X .J am es on S,\\ilkinson

EM.(

966) Studies n mental

liandirap. Part 1: Prevalence and distribu tion by clinical typ e and

severity of tlefert . A ch ires

of

Disensr in Cli ildliood 41:

228-38.

piovaleiice in S or th rrn Ircland...lcta Psy rhiu tricn AScnnclinctuica

4 0 2 0 3

11.

chiltlien

i n

the county ofA arlius.Denin ark.Ar/n Psych ialricn

Scandinauicn

48:

80-500.

24.Akessoii HO.( I O G i ) Severe men tal deficiency in a popdot ion in

Mrstcrn S\veden.A prelim inar y report...lc/a C;ete,lrtirnSlrttivtica

Jlrrlica 17: 43-7.

25.

Hu tte r JI,T izard .J.\\hitmore K.Cl,Q70) Editcafion. Health a n d

Brhavio,: I~ondon: ongman.

2G.Sorel

FM.(

952)

Frequencies of mental retardation in

.h i s te rdam,pnr t s

1 arid 11.[

I n Dutch.] Tijdschrijl v w r Soriale

Cenerskroide 50: 579-87 .G 11-20.

27. JIcDonaldAD.( 1973) Severely retarde d cliildren in Quebec:

preraleiice,caiises.aritlcare.A nierican Jo iir na l oJ.lleti/al

Dejciency 7&205-15.

28.1,emkau

P\ Imre

PD.( 1969) R esul tsofa f ieldepidemiologic

study.iinierican Jonrnnl of llrntal Dejciency 73: 58-63.

29.WaIlin L.( 1973)A stu dy of mental retardation (inoderate.severe

and profound) n a Swedish urban conirnuiiit3:Iii:ProrrPfli~igsf

the

Th ird Congress of the Inter nut

iotrct l

Asso rial ionf o r l he

Sc i r n l i j r s t u d y

o j d l e n t n l I l e j c i e n r y . T l i e

Hague.1) 189 -94.

.loiirnal ofNeiitnl Dejcienry Reaenrch

5: 12

-19.

mental retardation.Aniericun ./oitrnal of Slental Dejciency 78:

27-32.

32.Goidd

J.(1976)Language development an d non-verbal ski l ls i n

severely mentally retarded c1iildren:an epidemiological study

Joiirtial of . l lrn/al Dejiciency Resenrrh 20: 129-46.

33.Rernsen:\H.( 1976) Severe mental retard ation amo ng children in

the county ofdarlius,Dcnniark.A comm unity stud y

on

prevalence and provision ofse rvir e.dc /n Isycliiatricn

Scundinavica

51:

43-66.

in Queenslantl...l t s l r a ~ ~ ~ i ~/oicrnal o f , l l e ~ i k d elardalioii 4

20. Birch HG. Richardson SA, nirtl D. orobin G,lllsley It.(1970)

22.ScaIIy BG J I a c K a y DS.(964) Mental sul)normality and i ts

23. Brask BH.( 97,)P i e v a l e i i t ~ fmental retardat ion among

30.JlacKay DS.(971)J lenta l subnormali ty in Sor ther n Ireland.

31.(;ranat K,Grunat

S.(

1973) Below-a\-eragentelligence a nd

34. ReynoldsAR.( 1976)Theprevalence of known mental retarda t ion

69-73.

3.5. Lasona R.RidlerJIAC.Bowven H.Bra\-ery A t . 19 i 7 ) A n

etiological survey o ftlie severely retarded Hertfordshire children

who were born between

January

1,1965 and Deceh ber 31,1967.

Anrtr ican Joi irn al ofMedica1 C end irs

:

75-86.

36.Stein

Z,Susser

31,Saenger

C.(

1976) Mental retardatio n in

a

national populat ion ofyo ung men in the Netherlands. I .

prevalence of severe mental re tardation.An ierican Joicrnal

of

Epidemiology 10s.477-85.

37.Stein Z,SiisserBI,SaengerG.( 1976) JIental retardat ion n

a

national popula tion of

young

nien

i n

the N etherlands.1

I .

Prevalence of mild inent a1 retardati0n.A nierican

Joit

r n d 4

EpidPniiology

104:

5 b-G ).

38.Fropt

.JB.(

1977) Prevalence of mental handicap in the West of

Irelaiid.Joiir?inl

ofthe

IriJh .lledicalffssorinlioti 7 0 263-5.

39.Gustavson

K-H,Hag berg B,HagbergG,Sars K.( 977)Severe

mental retardation in a Swedisrh county. I . Epidemiology,

gestational age. birth weight and associated CN S handicaps in

children born l ~59 - 70 .d c f a a e d i al r ic a Sc a t td i nu i~ i r a8: 73-9.

4O.Gustavson K-H .Hag berg R,HngbergO.Sars

K.(

977)Severe

mental retardation in aSwvedish county. 1I.Etiologic and

pathoge netic aspects of rhildren born

1959-1970.Neuropadiatrie

8: 293-304.

4l .Gustavson K-H .Holmgren U,J on dI K,Blomquist

H

K.(

977)

Se\.eremc nt d retardation in children in a northern Swedish county

Jo trr nd of.llrntal Ilejcienc y Hesrurch 21:

161-80.

P2.Blo nqu ist HK.C ustavson 1;-H.Holmgren G.(

1981)

Mild niental

retar datio n in rliildren in a n orth ern Sw edish county. Jortrnalof

.llentnl DrjciencyHe.yearcli 25: 169-86.

43 HagbergC.l~e\\.erthr\,0lsson

.\ csterberg

R.(

1985)

AIild mental

retardation

in

Cot lieiiburg children born bet\veeii 1966-7$

Changes between two points in t ime. l l pa la Joi irnnl oj i l ledird

4.4.

itchell SdE\Voodt hor pe J.

I981

)Young

mentally Iiaiidicapped

adults in three

Inxidon

borouahs:I)revaleiice an d

degree

of

disabilit3:./orirtc/ of Epidenr iolog / a n d

Conr

n i n ni ly Henlth a5.

59-64.

retardation in four Finnish.birth cohorts. p s g l n Joiirnal of

.llerlicu/ Science44(suppl): 4 1-6.

4U.Elliott DLJacIison .JJI.C;raves.IP( l98 l)T he Oafordsliire mental

handicap register.llri/i.sh

Jledicnl Joii

rnal282: 789-92.

47 El \ \oodqJH,Darragh

M.(

1981)Severemental handicapin

Sor t l i e rn 1reland.Joitrnnl c~. l l en/a lDr j r i en q Hesrurch 25:

147-55.

4 8 . k Q u e e n

M3,Spen~e

\\:Uanier.l R.Pe iTira LH.\Vinsor EJT.

( 1985) Prevalence of niajor mental ietardotion and associated

disabilities

in the C anadian Maritime proviiices...lttiPricat~ ournal

ojJlrn lnl Drjr iency 91: 6 0 6

49.

I


8/8

. I

@.Stein

ZA.8usser

AN ( 1963)The social distri,bution of menta l

6

oa i t z

L.( 974)

Social factors in mental retardatio n.Socia l

66.Taft LT.( 980)Anorervieivofthe etiology ofmental retardation

retardation.dnierican Joitrnalof JlentalDeficieney 82811-41.

SrieticeandlMedicine8:105-12. i

nnd developm ental disabilities. 1n:JlcCormack

A l K di t or .

Precentioti of

Uenlal

Retardation

and

other Developmental

Disabilities. (Pedia tric Habilitation

vol.

1.)NewYork:hlarcel

Dekker.p3-13. i

67.Sarayanan HS.( 981)A study of th e prevalgnceof mental

retardation in southern 1ndia. l t i ler~iational'Joumalf Jfenlal

Health

10:

28-36.

68.Stein Z.DurkinA1,Belmont I,.( 1986)'Seriou~'mentaI etardation

in developing countries:a n epidem iologic approa ch.d?inn le of the

Serr

Yorkrlcndettsyof Science

477:

8-41.

mental retardation in Pakistan.infernationa1 Joiirqnl

of

Mental

Health

1 0

3-7.

ond severe mental r eta da tio n con1pared:experiences in eight l&s

developed countries. Upsaln Jou rnn l

of

illedical kien cc 44(suppl):

I

89

96.

. I

retarded persons.lndinn Pediatries 233 825-8.

I

69. Hasan Z.HasanA.( 1981)Report on a popul'ation survey of

7O.SteinZ. Relmont L , Durkiii

)I.(

1987)Jlild ]dental retardation

7 1. Sat spa thy

R

I.

prevelensi retardasi mental.pdf

Documents