Prevalence of intellectual handicap in Western Australia: a community study

To produce comprehensive community based data on individuals with intellectual handicap, the level of retardation, associated handicaps and demographic data.

Multiple sources of ascertainment were used to identify all children in birth cohorts, 1967-1976 inclusive, who had an IQ less than 70.

The majority of cases were ascertained through Western Australian government agencies that provide services for the intellectually handicapped. Other sources included the support branch of the education department, private schools and the children's hospital.

In all, 1602 children, aged between 6 and 16 years, fitted the study criteria.

The prevalence of intellectual handicap was found to be 8.9 per 1000 live male births and 6.3 per 1000 live female births with an overall rate of 7.6. The figures for mild, moderate, severe and profound retardation were 3.0, 2.4, 1.0 and 0.6 per 1000, respectively, with 0.8 per 1000 with an unknown IQ. Cerebral palsy occurred in 20% and epilepsy in 13% in addition to intellectual handicap. There was a significantly higher rate among those from rural compared with urban areas: 9.9 v. 6.5 per 1000 live births, respectively.

This comprehensive epidemiological data on intellectual handicap in Western Australia will be of value in the planning of services, including screening and genetic counselling, and for the evaluation of care. The rural preponderance, in particular, is worthy of further evaluation.