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Major Mental Handicap: methods and costs

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of- prevention

Ciba Foundation Symposium 59 (new series)

1978

Elsevier Excerpta Medica North-Holland Amsterdam - Oxford - New York

Major Mental Handicap: methods and costs of prevention

The Ciba Foundation for the promotion of international cooperation in medical and chemical research is a scientific and educational charity established by CIBA Limited - now CIBA-GEIGY Limited - of Basle. The Foundation operates independently in London under English trust law.

Ciba Foundation Symposia are published in collaboration with Elsevier Scientific Publishing Company I Excerpta Medica I North-Holland Publishing Company in Amsterdam

Elsevier I Excerpta Medica I North-Holland, P.O. Box 21 1, Amsterdam

Major Mental Handicap: methods and costs

fi 0

of- prevention


1978

Elsevier Excerpta Medica North-Holland Amsterdam - Oxford - New York

0 Copyright 1978 Ciba Foundation

All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, or by any information storage and retrieval system, without permission in writing from the publishers.

ISBN 0-444-90033-0

Published in August 1978 by Elsevier/Excerpta Medica/North-Holland, P.O. Box 2 11, Amsterdam and Elsevier/North-Holland Inc., 52 Vanderbilt Avenue, New York, N.Y. 1001 7.

Suggested series entry for library catalogues: Ciba Foundation Symposia. Suggested publisher’s entry for library catalogues: Elsevier/Excerpta MedicalNorth-Holland


236 pages, 34 figures, 43 tables

Library of Congress Cataloging in Publication Data

Symposium on the Cost of Prevention Major Mental Handicap, London, 1977 Major mental handicap.

(Ciba Foundation symposium; new ser., 59) Bibliography : p . Includes indexes. 1. Mental deficiency--Prevention--Congresses. 2. Mental deficiency--Prevention--Costs--

Congresses. 3. Neonatal intensive care--Congresses. 4. Prenatal care--Congresses. 5. Mental deficiency-Etiology-Congresses. I. Title. 11. Series. RJ506.M4S95 1977 618.9’28’58805 78-15495 ISBN 0-444-90033-0

Printed in The Netherlands by Van Gorcum, Assen

Contents

c . 0. CARTER Chairman’s introduction 1

E. ALBERMAN Main causes of major mental handicap: prevalence and epidemiology 3 Discussion 12

c. M. DRILLIEN Aetiology of severe handicapping conditions in early childhood 17 Discussion 24

B. HAGBERG Severe mental retardation in Swedish children born 1959-1970: epidemiological panorama and causative factors 29 Discussion 4 1

c. J. HOBEL ABCs of perinatal medicine 53 Discussion 72

E. 0. R. REYNOLDS Neonatal intensive care and the prevention of major handicap 77 Discussion 103

c . AMIEL-TISON A method for neurological evaluation within the first year of life: experience with full-term newborn infants with birth injury Discussion 120

107

General Discussion 127

P. M. FITZHARDINGE, E. KALMAN, s. ASHBY and K. E. PAPE Present status of the infant of very low birth weight treated in a referral neonatal intensive care unit in 1974 139 Discussion 144

V

v1 CONTENTS

A. STEWART, D. TURCAN, G. RAWLINGS, s. HART and s. GREGORY Outcome for infants at high risk of major handicap Discussion 164

15 1

R. L. AKEHURST and s. HOLTERMANN Application of cost-benefit analysis to programmes for the prevention of mental handicap Discussion 185

173

M.T. CHAPALAIN Perinatality: French cost-benefit studies and decisions on handicap and prevention 193 Discussion 204

Final discussion Priorities for obstetric intervention 207 Group with IQs of 50-70 2 10 Research priorities 213 UK priorities 214 Ethics 219

Index of contributors 221

Subject index 223

Participants Symposium on The Cost of Preventing Major Mental Handicap, held at the Ciba Foundation, London 7th - 8th November, 1977

c . 0. CARTER (Chairman) MRC Clinical Genetics Unit, Institute of Child Health, 30 Guilford Street, London WClN IEH, UK

E. ALBERMAN Department of Community Health, London School of Hygiene & Tropical Medicine, Keppel Street, Gower Street, London WClE 7HT, UK

c. AMIEL-TISON Centre de Recherches de Biologie du DCveloppement Foetal et Neonatal, Hdpital Port Royal, UniversitC RenC Descartes, 123 Boule- vard de Port-Royal, 75014 Paris-Cedex 14, France

J. D. BAUM Department of Paediatrics, University of Oxford, The John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK

M.T. CHAPALAIN Bureau des Etudes et du Plan - Direction GCnCrale de la SantC, Ministere de la SantC et de la SecuritC Sociale, 1 Place Fontenoy, Paris 75007, France

F. COCKBURN Department of Child Health, University of Glasgow, Royal

P. A. DAVIES Department of Paediatrics & Neonatal Medicine, Hammersmith

Hospital for Sick Children, York Hill, Glasgow G3 8SJ, UK

Hospital, Du Cane Road, London W12 OHS, UK

c. M. DRILLIEN Armitstead Child Development Centre, 94 Monifieth Road, Broughty Ferry, Dundee, UK

J. M. DRISCOLL Department of Pediatrics, College of Physicians & Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA

P. M. DUNN Department of Child Health (University of Bristol), Southmead Hospital, Southmead Road, Bristol BS 10 5NB, UK

VII

VIII PARTICIPANTS

P. M. FITZHARDINGE Neonatal Follow-up Programme, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada M59 1x8

Department of Pediatrics (University of Goteborg), East Hospital, S-416 85 Goteborg, Sweden

Department of Pediatrics (University of Goteborg), East Hospital, S-416 85 Goteborg, Sweden

s. HOLTERMANN Economic Adviser’s Office, Department of Health & Social Security, 151 Great Titchfield Street, London WlP 8AD, UK

c . J. HOBEL Department of Obstetrics and Gynecology, UCLA School of Medicine, Harbor General Hospital, 1000 West Carson Street, Torrance, California 90509, USA

B . HAGBERG

G. HAGBERG

F. KUBLI Universitats Frauenklinik, Voss Strasse 9,6900 Heidelberg 1, West Germany

J. L. MICHELI Department of Paediatrics (University of Lausanne), H6pital Cantonal Universitaire, 10 1 1 Lausanne, Switzerland

E. 0. R. REYNOLDS Department of Paediatrics, University College Hospital,

N. R. c . ROBERTON Department of Paediatrics, Addenbrooke’s Hospital, Hills

London WC 1, UK

Road, Cambridge CB2 2QQ, UK

w. A. SILVERMAN 90 La Cuesta Drive, Greenbrae, California 94904, USA

A. STEWART Department of Paediatrics and Obstetrics, University College Hospital, London WC 1, UK

B. STRIPP Division of Lung Diseases, National Heart, Lung and Blood In- stitute, Bldg WW, Rm 6A10, National Institutes of Health, Bethesda, Maryland 200 14, USA

00290 Helsinki, Finland K. TERAMO Department of Obstetrics & Gynecology, University of Helsinki,

K. WINSHIP Department of Health & Social Security, Room B. 1108, Alex- ander Fleming House, Elephant & Castle, London SE1 6BY, UK

R. W. WINTERS Department of Pediatrics, College of Physicians and Surgeons of Columbia University, 630 West 168th Street, New York, NY 10032, USA

Editors: KATHERINE ELLIOTT (Organizer) and MAEVE O’CONNOR

Chairman’s introduction

C. 0. CARTER

MRC Clinical Genetics Unit, Institute of Child Health, London

The main point of our meeting is to discuss the extent to which severe mental handicap may be prevented by better prenatal and perinatal care and to consider the cost of providing such care.

First the problem must be set in the perspective of the aetiology of severe mental retardation and the opportunities for, and perhaps the relative cost of, prevention of other types of severe mental retardation, such as those due to chromosomal and inborn metabolic errors. The first contribution, by Dr Alberman, will set out this perspective. The birth frequency of severe mental retardation, like that of the major congenital malformations, has been little affected by the public health measures which have been so successful in reducing the rate of infantile and more recently perinatal mortality. The prevalence at school age is usually taken as between 3 and 4 per 1000, and Professor Hagberg will be giving us information on this. Such reduction as there has been is perhaps largely confined to Down syndrome and is the consequence of the reduction in births at late maternal ages. We now have a clear picture of the aetiology of half to two-thirds of all cases of severe mental retardation. Of the genetic types trisomy 21 is outstanding, being itself responsible for about a third of all severe cases of mental retardation at primary school age. This group, as Dr Alberman will tell us, is now amenable to secondary prevention by prenatal diagnosis and abortion, though we have no way yet of preventing the primary error in gametogenesis. Cost-benefit analysis for such prenatal screening and abortion has been made in two or three countries and these measures appear to be cost-effective at least down to maternal age 38. Monogenic disorders are less important, perhaps accounting for 10 to 1576, and again Professor Hagberg has some up-to-date figures from two areas of Sweden which show the expected differences in relation to inbreeding. Known prenatal environmental causes are a relatively small

1

C . 0. CARTER 2

group: intrauterine rubella is responsible for perhaps less than 1 % of cases and is now preventable; cytomegalovirus infection is possibly more frequent than rubella, though we need more information on this. Maternal alcoholism does not appear to be making any significant contribution to severe retardation in the UK at present, and smoking in pregnancy perhaps contributes only indirectly, through low birth weight for dates. Spina bifida again makes a small and now largely preventable contribution. Clear-cut postnatal causes, such as cerebral and meningeal infections, again make only a small contribution and are preventable. Kernicterus due to rhesus incompatibility is already preventable and mostly prevented.

This leaves, say, 40% of cases with no certain cause and Professor Hagberg will be reminding us that it is in this group that associated neurological disorders such as cerebral palsy, epilepsy and disorders of the senses are relatively common. Some cases in this group (Dr Drillien will be giving us an estimate of the proportion) are due to perinatal events, mainly asphyxia and cerebral haemorrhage. Probably this is not a large group in relation to all severe mental retardation, but these conditions are in part preventable and well worth preventing. A more difficult group perhaps, both for evaluation of frequency and for attempting prevention, are the cases with prenatal acquired causes other than infection. Dr Hagberg’s Swedish colleagues have described this group as having the ‘fetal deprivation syndrome’; it includes babies whose mothers suffered from associated bleeding in pregnancy, placental infarction, toxaemia and diabetes. Dr Hobel will discuss some of the methods available to the obstetricians dealing with high-risk pregnancies-methods that may reduce the impact of such prenatal causes. Professor Reynolds, Dr Fitzhar- dinge and Dr Stewart will discuss the methods available to the neonatal paediatrician for preventing perinatal damage. Not only may the survival rate of such high-risk infants be improved, but the rate of survival without mental handicap. Dr Amiel-Tison will discuss methods of measuring some of the less severe neurological defects.

Finally, if severe mental retardation can be prevented by better obstetric and neonatal care, what is the cost? Ms Holtermann will discuss this and then Dr Chapalain will tell us something of the experience in France, which has recently reduced its infant mortality from well above to well below that of England and Wales.

Main causes of major mental handicap: prevalence and epidemiology

EVA ALBERMAN

Department of Community Health, London School of Hygiene and Tropical Medicine, and Paediatric Research Unit, Guy5 Hospital Medical School, London

Abstract The prevalence of educational subnormality of a severe form (between 3 and 3.6 per thousand children of school age) and the prevalence ofcerebral palsy (between 2 and 2.4 per thousand) have been fairly stable up to recent years. This stability has also applied to the relative proportions of the different major causes contributing to the handicaps.

Where the ascertainment of such conditions is good, their prevalence monitored and the life expectancy of affected individuals estimated, any changes in prevalence can be used to measure the effectiveness of new forms of prevention, or alternatively to indicate the existence of new environmental hazards. Only a multi-pronged campaign against many of the recognized causes will have a substantial impact on prevalence.

The term ‘major mental handicap’ is a very broad one, encompassing an enormous variety of pathological conditions, and it can be defined in many different ways. In practice, there is general agreement on one group to be included: those individuals needing lifelong and constant care because of their inability to look after themselves. It seems that an arbitrary cut-off point of an IQ of below 50 defines such a group and, following Kushlick (1965), it has become usual to add to this group individuals with Down syndrome, if their IQ has not been tested. With these I will group, for the purposes of this symposium, the heterogeneous collection of conditions known as cerebral palsy, which is often, but not always, associated with mental defect.

There has been a vast amount of work on the prevalence and epidemiology of the conditions which together make up the group I have defined in this way, and one factor stands out clearly. This has been an apparent stability in over-all age-specific prevalence, which is in marked contrast to the large variations in reported prevalence of milder forms of mental defect. The latter can be shown to vary strikingly with cultural factors, and with differing

3

4 E. ALBERMAN

educational provisions for this special group. The severe forms of handicap do not show such variations, and by common consent can be regarded as largely biological or pathological in origin, rather than cultural or just the tail of a normal distribution.

The actual prevalence of major mental handicap as I have defined it depends on several basic factors. Most directly, it depends on the incidence at birth of its constituent conditions. This in turn depends on the frequency in the population of parents at high risk of producing offspring with specific abnormalities. After this, the ultimate prevalence at different ages will depend on the survival of affected individuals. The reported prevalence will also depend on the thoroughness of ascertainment of the handicapped individuals (ascertainment is the technical term used by educational authorities who have a statutory duty to seek out children who will require special educational provision). Considering the very complex nature of these interacting factors, and the extremely large number (probably in the thousands) of different conditions making up the total group, I never fail to be surprised at the stability of the prevalence of handicap, both over the past 20 years in the UK and in many cases also between countries.

This stability can be demonstrated by reference to specific well-recognized disorders such as Down syndrome; or to such a heterogeneous group as the cerebral palsies; or to the reports of the so-called ‘administrative prevalence’, at different ages, of individuals in need of special care by reason of their handicap.

DOWN SYNDROME

Table 1 shows estimates, from different sources and at different times, of age-specific population incidence rates of Down syndrome at birth. Overall the Swedish rates are consistently higher, but Lindsjo (1974) shows that, with the exception of the small group of mothers in the very oldest age-band, these differences can probably be ascribed to better ascertainment in Sweden. Allowing for this, there is on the whole a close similarity between the rates, particularly in the age-groups with the largest numbers, with the well-known steep rise with increasing age. Such examples can be multiplied many times. This is surprising, because even Down syndrome is heterogeneous in origin, with about 3% of the cases in most reported series resulting from a chromosomal translocation and the remainder from primary trisomy 2 1. The variation of risk with age is seen only with the latter.

EPIDEMIOLOGY OF MAJOR MENTAL HANDICAP 5

TABLE 1

Incidence per thousand births of Down syndrome by maternal age group (adapted from LindsjG 1974)

Maternal aRe

-19 20-24 25-29 30-34 35-39 40-44 45-

Sweden 1968-70 (331 000 births)

0.59 0.74 0.88 1.46 3.74

14.96 62.10

UK 1951-63 ( I 700 000 births)

0.45 0.49 0.65 1.08 3.37

10.74 24.94

Australia 1942-57 (780 000 births)

0.42 0.62 0.82 1.13 3.45 9.80

21.56

CEREBRAL PALSY

In view of the difficulties of diagnosis and classification of cerebral palsy it is not surprising that the variation in reported rates is a little larger than for Down syndrome. Table 2 summarizes the data from the literature presented by Henderson (1961) and adds more recent data from the National Child Development Study (Davie et al. 1972). The most carefully ascertained studies

TABLE 2

Reports of the prevalence of cerebral palsy in Great Britain in children ofschool age (adapted from Henderson 1961)

Rates per thousand No. of studies

Range of rates reported in children of school age in 19 studies in UK, 1948-1957

< I 1.0-1.4 1.5-1.9 2.0-2.5

National Child Development Study, 1965 2.4 (Davie et al. 1972)

included were those from Scotland, Henderson’s (1961) from Dundee and Ingram’s (1964) from Edinburgh, and their rates were 2.04 and 2.3 per thousand, respectively. Together with the National Child Development Study rate of 2.4, and with reports from overseas suggesting about the same level in the 1950s and 1960s, we may accept that the real prevalence at that time was between 2 and 2.4 per thousand children of school age. Moreover, there has been fairly good agreement from many different sources on the proportions of different types of cerebral palsy found (Mitchell 1961). Table 3 gives the proportion of the different types found by Henderson (1961) and his col-

6 E. ALBERMAN

TABLE 3

Distribution of different types of cerebral palsy (adapted from Henderson 1961)

Dundee Edinburph Bristol (Henderson 1961) (Ingratn"!964) (Woods 1957) % s %

Hemiplegia 37.5 36.1 36.6 Double hemiplegia 1.3 Diplegia 38.3 Ataxic diplegia 2.9 Ataxia 1.7 Dyskinesia 8.4 Other 10.0

Different 7.2 classification 8.2 1 .o

leagues in the population study carried out in Eastern Scotland in 1955, and compares this with other similar studies.

For most published surveys the relative proportion of the main aetiological features is also fairly constant. Typical of the findings are those described by Henderson (196 1). In this series of 240 children, comprising all known cases from Eastern Scotland in children of school age in 1955, 12% of all cases were of 'postnatal origin', a term which included kernicterus; and the incidence of birth weights of 2500 g or less was 27.5% and of twins 10%. In the subgroup of cerebral diplegia, well known to be associated with premature births, the incidence of low birth weight was 58.9%.

We can therefore estimate that even a halving of the incidence of low birth weight, or alternatively the effect of reducing long-term defects in such births by 50% or more, could only reduce the prevalence of cerebral palsy by 13%, all other factors remaining equal. It will be seen later that the effect of this reduction in cerebral palsy on the prevalence of severe mental defect would be considerably smaller.

In most series for which data are available, about 25% of children with cerebral palsy have an IQ of below 50, and a further 20% or so have an IQ between 50 and 70 (Cockburn 1961).

EDUCATIONAL SUBNORMALITY (SEVERE)

As I said earlier, the very mixed group classified as educationally subnormal (severe) itself showed a surprisingly stable prevalence within age-bands. Indeed, there is evidence that much of the reported variation in prevalence is due to difficulties in ascertainment, for in all studies the reported prevalence rises with age to a maximum at ages 15-19. It is presumed that in the younger and the older populations ascertainment is incomplete. Table 4 gives the


TABLE 4

Comparison of the prevalence rates of IQ under 50 in age groups where all subjects are likely to be known (adapted from Birch et al. 1970)

Age of children

England & Wales (L.ewis 1929) 1925-1927 urban 7-14

Middlesex (Goodman & Tizard 1962) 1960 7-14 1960 10-14

Salford (Susser & Kushlick 1961) 1961 15-19

Wessex (Kushlick 1964) 1964 county boroughs 1964 counties

15-19 15-19

Baltimore, MD, USA (Lemkau et al. 1943) 1936 10-14

Aberdeen, Scotland 1962 8- 10

Edinburgh, Scotland (Drillien et al. 1966) 1962-1964 7-14

Quebec, Canada (McDonald 1973) 1966-1969 10

England, Wales & Scotland (Frew & Peck- ham 1972)

1969 11

Total rate per 1000 with I Q < 50

3.16

3.45 3.61

3.64

3.54 3.84

3.3

3.7

4.9

3.8

3.6

prevalence of this group in several studies both inside and outside the United Kingdom and shows how little variation there is within the age-ranges indi- cated, given the difficulties of full ascertainment.

Table 5 gives the proportions of different conditions found in a series of severely retarded children in Hertfordshire between 1965 and 1967 (Laxova et al. 1977) and in whom particular care was taken to diagnose the cause where possible. The general findings are fairly typical of many other series, with Down syndrome accounting for about one-third of all cases in most published studies. Local variations may occur, as in areas where neural tube defects are unduly common, or in remote areas, such as some parts of Sweden, where certain genetically determined conditions are frequent, but in general the pattern has been very stable.

E. ALBERMAN 8

TABLE 5

Distribution of different types of condition in severely retarded children in Hertfordshire, 1965-1967 (adapted from Laxova et al. 1977)

Distribution ( n = 146) ( w

Genetically determined Down syndrome

Trisomy 2 1 Translocation

Other

Epilepsy - idiopathic

Neural tube defect

Cerebral palsy

Postnatal brain damage (including one case of rubella syndrome)

Other

32.2 30.1 2.1

16.5

1.4

4.8

6.8

4.1

34.2

All 100

IMPLICATIONS OF THE STABILITY FOUND

It is because of the generally stable pattern of prevalence that it should be possible to plan and to evaluate the most effective methods of prevention. With such a heterogeneous collection of conditions, one must study each condition individually as far as possible and, for each, determine the major aetiological factors and the extent to which they are preventable. Given a baseline derived from well-ascertained studies, substantial changes in trend should be detectable, if surveillance of incidence and prevalence of conditions such as I have discussed is maintained.

THE FORMS WHICH PREVENTION CAN TAKE

Prevention of these conditions may take many different forms, largely related to the nature of the cause of the defect. Thus, for purely genetically determined conditions, the only form of prevention may be the avoidance of conception by women known to be at high risk, or termination of pregnancy where an affected fetus can be diagnosed. For maternal infection, prevention can take the form of preconceptional immunization together with termination


if immunization fails. More complex is the situation where the damage is caused at or around the time of birth. There is increasing evidence, as will be discussed later in this symposium, that a programme of: intensive antenatal surveillance; monitoring for, and immediate relief of, distress during labour; resuscitation at birth; and excellent neonatal care, will do much to prevent permanent brain damage in a potentially normal infant. It is extremely important to distinguish between the potentially normal and the irreversibly abnormal fetus. In the latter, prevention of perinatal or later death must inevitably lead to an increase in handicapped survivors. In the former, there is a fine balance between death, impairment and the intact survivor which can, in optimal circumstances, be pushed over in favour of the intact healthy infant. Later in the symposium Professor Hagberg will no doubt be showing how, in Sweden, even in the face of a continually falling perinatal mortality rate, handicaps due to perinatal complications seem to be decreasing in survivors.

These are general observations which can be converted into fairly sound predictions about the effect of preventive action on the incidence of severe handicaps. The observed fulfilment of such predictions acts as a confirmation of aetiological hypotheses and constitutes a good clinical trial of the actions taken. Moreover, one can also estimate which methods of prevention will be most cost-effective, in the sense of preventing the most handicaps.

Thus, for Down syndrome, it has been shown that maternal age is the most important risk factor. It can be predicted to what extent a shift in maternal age distribution should reduce the crude incidence, and indeed a recent publication from Sweden (Gustavson et al. 1977) shows that this prediction seems to be correct. In addition, but at infinitely greater cost, a programme of prenatal diagnosis and termination of affected fetuses can be commenced; and again data are now accumulating all over the world on the cost-effectiveness of such action, with different arbitrary cut-off points for screening. Since in the past Down syndrome has accounted for a third of all cases of severe subnormality, such a programme could have a considerable impact on over-all prevalence of the latter, unless the prolongation of life of affected survivors balances the reduction in affected births.

For cerebral patsy, one can also predict the effect of altering the incidence of high-risk factors such as low birth weight, or of preventing permanent damage at the birth of vulnerable babies. Again, Swedish workers are in a position to evaluate such measures. The impact on the prevalence of severe subnormality of reducing the incidence of cerebral palsy will be far less than for Down syndrome, because cerebral palsy is a much smaller constituent of the total (7% in the study by Laxova et al. 1977, 19% in that by Gustavson et al.

E. ALBERMAN 10

1977). However, the importance of the reduction in the number of children with severe degrees of cerebral palsy is enhanced by the probability that this reduction may be accompanied by a shift towards the normal of the whole range of brain-damage in high-risk children.

Similarly, one can predict the effects of genetic counselling on the incidence of certain inherited conditions, or of antenatal screening, diagnosis and termination of fetuses with a neural tube defect. Some idea of the effect of tackling only one of the biochemical disorders contributing to the total load of severe mental defect can be obtained from the series described by Laxova et al. (1977) where only one in 146 cases was due to phenylketonuria, one of the conditions in which most effort has been expended on prevention. Clearly only a multi-pronged attack on the many different causes can have a substantial impact on prevention, and this is now happening.

I have rearranged the data presented by Laxova et al. (1977), which are very similar to the figures from Sweden (Gustavson et al. 1977), to show the reduction that could occur if theoretically preventable cases were prevented (Table 6). Had these babies been born today (or next year) the over-all prevalence of this group might have been reduced by 20.5%.

If a group of preventable conditions is reduced, it follows that the proportion of the total contributed by conditions not so easy to prevent will increase. Another indicator of advance in prevention will therefore be the proportion of

TABLE 6

Possibly preventable conditions as estimated from the Hertfordshire study (Laxova et al. 1977)

‘Preventable cases’ No. of cases

20% of Down syndrome (estimated proportion in mothers aged 40+) 9

Genetic conditions with family history 5

6 Cerebral palsy with birth complications

Post-vaccination encephalitis Meningitis Rubella syndrome Cardiac arrest during exchange transfusion

Neural tube defects 5 (excluding sibs after I affected case)

Total ‘preventable’ cases 30 (20.5%)

Remaining cases 116 (79.5%)

)I __-. _____~_______ -~


‘preventable’ to ‘unpreventable’ (mostly genetically determined) conditions, and this may be easier to measure than changes in incidence.

THE POSSIBILITY OF INCREASES IN THE INCIDENCE OF HANDICAP

However, one must also look at the other possibility, namely that new hazards are actually contributing towards an increase in some of the conditions we have been considering. To come back to Down syndrome, Lindsjo (1974) has suggested that the higher rates for age-specific incidence seen in Sweden in recent years may be a real effect, not just due to improved ascertainment, and may reflect such new hazards. An increase in pre-conceptional radiation received by the female population both inside and outside the medical services could have such an effect, albeit a small one (Alberman et al. 1972), and chromosome anomaly in offspring after the mother has taken female sex hormones in the form of contraceptives or therapeutic agents (Carr 1967) could constitute another such hazard, although there is no proof of this yet. Such risks might theoretically also contribute towards an increase in other genetically determined conditions, although again there is no evidence of such an effect.

For cerebral palsy, there was the suggestion, based on the work of Cross (1973) and his colleagues, that the limitation in the amount of oxygen given in the neonatal period after the retrolental fibroplasia investigations may have caused not only many excess deaths but also many excess cases of cerebral palsy. We have no evidence that this actually happened, but the possibility should act as a sharp warning of the possibility of adverse iatrogenic effects, and for this reason alone one must stress the necessity for close monitoring of the incidence of defects.

To end on an optimistic note, what data there are on the incidence of the handicaps we are considering today suggest that on balance the changes observed are in a favourable direction. We are now ‘nibbling away’ (Professor Polani’s term) at the defined constituent conditions that contribute to the total load of severe congenital handicap. Knowledge of previous prevalence and causes will guide our preventive campaigns and help us to evaluate our actions.

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CARR, D. H. (1967) Chromosomes after oral contraceptives. Lancet 2 830-83 I COCKBURN, J. M. (1961) Psychological and educational aspects, in Cerebral Palsy in Childhood and

CROSS, K. W. (1973) Cost of preventing retrolental fibroplasia. Lancet 2, 954-956 DAVIE, R., BUTLER, N. & GOLDSTEIN, H. (1972) From Birth to Seven, p. 163, Longman, in association

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Adolescence (Henderson, J. L., ed.), Livingstone, Edinburgh

with the National Children’s Bureau, London

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LINDSJO, A. (1974) Down’s syndrome in Sweden. Acta Paediatr. Scand. 63, 571-576 MCDONALD, A. D. (1973) Severely retarded children in Quebec: prevalence, causes and care. Am.

MITCHELL, R. G. (1961) Comparison with other cerebral palsy surveys, in Cerebral Palsy in

SUSSER, M. W. & KUSHLICK, A. (eds.) (1961) A Report on the Mental Health Services in the City of

WOODS, G. E. (1957) Cerebral Palsy in Childhood, Wright, Bristol

J . Ment. Defic. 78, 205-215

Childhood and Adolescence (Henderson, J . L., ed.), Livingstone, Edinburgh

Sa,fordfor the Year 1960, Salford Health Department

Discussion Reynolds: A ‘cause’ means something different to an epidemiologist and to

a perinatal physician. For example, the cause of cerebral palsy to me is not low social class or low birth weight but the insult-such as hypoxia-which pro- duces the damage to the brain. This implies that there are two intervention points. We can improve the social status of the population and reduce the incidence of low birth weight so as to prevent conditions being set up in which damage to the brain can occur. Failing this, we have to try our best to prevent


the organic insults which do the actual damage. This is a conceptual point which we shall be meeting again.

Taking an IQ of below 50 as an index of major handicap is a very hard-line definition, Dr Alberman. The very large component of genetic illness in infants with IQs as low as this is precisely what I would expect. To me, major handicap refers to someone who can’t lead a normal life in society, and a lot of people with IQs between 50 and about 70 are like that. Does the distribution of the causes of major handicap differ, in the UK, between those with IQs below 50 and those with IQs between 50 and 70? I would speculate that major handicap in the latter group is much more amenable to perinatal interven- tions.

AZberman: You are right about the different points of intervention. I also agree entirely with your comment about the definition of major handicap. I chose the definition of an IQ below 50 only because the data are available and this group is the easiest one to measure.

Much less information has been published about the prevalence of IQs of 50-70 and this group would largely overlap the culturally determined group.

Silverman: I suggest there is a conceptual problem when we begin to talk about ‘culturally determined effects’. For example, the perception of inca- pacity is, to a large extent, culturally determined. The disabled community (a distinct subculture) asks us to make a clear distinction between the words ‘handicap’ and ‘disability’. The first term is essentially a social judgement. In Western cultures it reflects temporal professional views and it guides social actions. In the recent past, children with Down syndrome were reared in institutions on the advice of physicians; now they are often reared at home because professional views have changed. When the blind and cerebral pal- sied decide that they are disabled but not handicapped, they achieve a degree of independence from professional judgement which is extremely important. Perceptions about handicap and disability vary widely in different social strata. In a plural society like the United States these variations cannot be ignored.

Stewart: Dr Silverman referred to the cultural and social definitions of handicap and disability. Whether a blind person is considered to be handicapped is obviously open to discussion but in order to overcome disability and to achieve independence these individuals have to undergo very extensive and expensive training. Therefore, in considering the effect of a problem like that on the individuals concerned and their families, or on society, we must remember what it costs, in terms of human effort and finance, to give such a person their independence. This is also true of a child with severe cerebral palsy, even if his IQ is above 50.

14 DISCUSSION

Kubli: Children with Down syndrome account for about a third of the cases with preventable mental handicap. Among the possibly preventable cases (Table 6) you included nine with Down syndrome, Dr Alberman. This is nearer 10% than 30% of the preventable cases.

Alberman: I was trying to show an example of what is practicable at the moment. Whereas population screening for neural tube defects will almost certainly be practicable within the next few years, I don’t see that population screening for Down syndrome will be practicable in our present state of knowledge, though we may be able to bring the age for screening down to 38.

Kubli: Is screening for Down syndrome done for women of 40 now in the UK?

A lberman: Yes, but only for a small proportion. Carter: Copenhagen is, I believe, doing best at that, with an uptake of well

over 40% down to age 40 (M. Mikkelsen, personal communication). Hagberg: In Goteborg we have had a screening programme for about five

years in which all mothers of 35 years of age or older are screened at the 16th week of gestation for Down syndrome.

Dr Alberman stated that maternal age is going down. This fact has contributed to a significantly decreased incidence of severe mental retardation in the northern parts of Sweden through 1959-1970. This change had already occurred in Uppsala (middle-east Sweden) before 1959.

Davies: One of the practical problems where screening is concerned is that if it is to have its full effect women will have to present themselves at a suitably early stage in pregnancy. As many as 45% of them in some parts of the UK may not do so (Clarke 1977). How do we get around this problem?

Curter: There are financial and other methods, which we shall be discus- sing later.

Dunn: I think Professor Reynolds put his finger on a very important point. A much greater proportion of infants with IQs of 50-70 than in the group with IQs below 50 receive their insults in the perinatal period. The trouble is that it is often difficult to prove. Because of lack of data we tend to ignore the subject. My own experience over the years is that most of the infants that I sub- sequently have to refer to the neuropaediatrician because of handicap, are the same babies as have caused worry in the neonatal period because of some problem such as hypoglycaemia, hyperbilirubinaemia, hypoxia, poly- cythaemia, apnoeic attacks, or because of abnormal neurological behaviour. Dr Alberman said that some 20% of cases of handicap were preventable. I think many clinicians would feel that this is an underestimate and that there is a big preventable aspect in the perinatal period.

Roberton: I would like to comment on the role of perinatal involvement in

major mental handicap: methods and costs of- prevention 0€¦ · prenatal care--congresses. 5....

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