Incidence and prevalence of type 1 (insulin-dependent) diabetes mellitus in Icelandic children 1970-1989.

Through use of primary and secondary data sources for registration and validation, the incidence and prevalence of Type 1 (insulin-dependent) diabetes mellitus in children aged 0-14 years in Iceland has been completely ascertained for the years 1970-1989. The age-adjusted mean annual incidence per 100,000 for the 20-year period was 9.4 (95% confidence interval 7.8-11.3); similar for boys (9.9; 7.7-12.7) and girls (8.8; 6.7-11.5). Between 1970-1979 the incidence was 8.0 (6.0-10.6) and between 1980-1989 it was comparable at 10.8 (8.4-13.8) (p greater than 0.10). By Poisson regression analysis the variation in incidence was related to age at diagnosis (p less than 0.001), while a linear trend for calendar year at diagnosis did not reach statistical significance (p = 0.07). A quadratic curve, however, better described the temporal variation in incidence (p less than 0.05). The total prevalence per 1,000 by the end of 1979 and 1989 was similar, 0.45 (0.30-0.65) and 0.57 (0.40-0.79), respectively. In conclusion, this study confirms that both the incidence and prevalence of childhood Type 1 diabetes in Iceland are low compared to the other Nordic countries. The findings may suggest a causative role for environmental factors that are not related to latitude or ambient temperature.