Intellectual disability in Western Australia

OBJECTIVE: To investigate the prevalence of intellectual disability in Western Australia (WA), its causes, prevention, and trends over time. METHODOLOGY: Data from an administrative database of intellectual disability in WA were used to report on the trends in intellectual disability in childhood. RESULTS: The prevalence of intellectual disability was 8.3 per 1000 live births in 1980-90. For half the cases, there was no known cause for the intellectual disability. Down syndrome accounted for 14 to 15% of all cases. Since the introduction of newborn screening, no WA-born child participating in the screening program has been diagnosed with intellectual disability as a result of either phenylketonuria or congenital hypothyroidism. The rate of autism spectrum disorders rose from three to six per 10 000 in the 1980-83 WA birth cohort to 10-13 per 10 000 for the 1989-92 cohort. CONCLUSIONS: Recent linkage of this administrative database to the WA Maternal and Child Health Research Data Base provides a unique opportunity for more detailed investigation of intellectual disability and its risk factors in a large, well-ascertained population of children.