PREVALENCE AND TIME TRENDS OF DISABILITIES IN SCHOOL-AGE-CHILDREN

Background. Although the evolution of the prevalence of cerebral palsy is now well documented, much less is known about the evolution of the prevalence of other disabilities such as mental retardation, sensoria l defects, autism and psychosis. The aim of this paper is to determine those trends. Methods. A population-based survey was carried out in 1 992-1993 in three French 'departements'. All disabled children born be tween 1976 and 1985 and receiving a special education and/or financial assistance were systematically registered. Results. The comparison of three cohorts of children born in 1976-1978, 1979-1981 and 1982-1984 using the test for trend in proportion showed a significant decrease ( P=0.03) in the prevalence of severe mental retardation, after exclusio n of Down syndrome. This decrease was significant for severe mental re tardation associated with psychosis. The time trend prevalence for cer ebral palsy increased (P=0.03) but was irregular. The time trend preva lence of other disabilities (other motor defects, severe sensorial dis abilities, autism and psychosis) did not change significantly. A detai led analysis of severe mental retardation and cerebral palsy was perfo rmed by geographical area, age at first registration and type of disab ility. Conclusion. The increase in prevalence of cerebral palsy is pos sibly due to earlier registration of disabled children. The decrease i n prevalence of severe mental retardation does not seem to be due to r ecruitment bias, but there is a possibility of classification bias.