Type 1 (insulin-dependent) diabetes in Tasmania: prevalence and apparent regional differences.

The results of a cross-sectional study of Type 1 (insulin-dependent) diabetes in the total population of Tasmania are described. Tasmanians, predominantly of British origin, live in a temperate island situated to the south-east of mainland Australia. For males and females respectively, prevalence in 1984 was 1.1 +/- 0.1 and 0.9 +/- 0.1 per 1,000 at all ages, 0.6 +/- 0.2 and 0.5 +/- 0.2 per 1,000 in subjects aged 0-14 years, rising to 1.2 +/- 0.2 and 1.1 +/- 0.2 per 1,000 in those aged 0-29 years. Prevalence in the 0-19 year age range was 0.8 +/- 0.2 per 1,000 in both sexes. Prevalence fell in both sexes from the third decade of life. A statistically significant excess in prevalence was found in the urban, as compared with the rural, sector of the community. The urban relative risk was greatest in subjects aged 10-19 years. According to reported month of onset (commencement of insulin treatment) there was a suggestion of seasonal trend in the rural, but not in the urban subjects. Longitudinal studies of Type 1 diabetes in Tasmania are now required if these findings are to be confirmed, and their possible aetiological implications explored.