Prevalence of major mental retardation and associated disabilities in the Canadian Maritime Provinces.

A cross-sectional survey of the prevalence of major mental retardation in 7- to 10-year-olds in the three Canadian Maritime provinces was carried out in 1980. Case ascertainment from multiple sources was considered to be virtually complete and resulted in a study group of 307 children, for whom 72% of the parents consented to personal data collection. The overall regional prevalence of major mental retardation was 3.65/1,000. Variation in county prevalence rate (based on parental residence at the time of birth) was associated, by regression analysis, with maternal age, areas of greater population concentrations, and number of physicians per capita. These associations were still present when children with Down syndrome were excluded from the analysis. Speech and behavior disorders and epilepsy were the major associated disabilities.