The incidence of Type I diabetes has not increased but shifted to a younger age at diagnosis in the 0–34 years group in Sweden 1983 to 1998

Abstract

Aims/hypothesis. To analyse the incidence of Type I (insulin-dependent) diabetes mellitus in the 0–34 years age group in Sweden 1983–1998. Methods. Incidence and cumulative incidence per 100 000 and Poisson regression analysis of age-period effects was carried out using 11 751 cases from two nation-wide prospective registers. Results. Incidence (95%-CI) was 21.4 (20.8–21.9) in men and 17.1 (16.6–17.5) in women between 0 and 34 years of age. In boys aged 0–14 and girls aged 0–12 years the incidence increased over time, but it tended to decrease at older age groups, especially in men. Average cumulative incidence at 35 years was 748 in men and 598 in women. Cumulative incidence in men was rather stable during four 4-year periods (736, 732, 762, 756), while in women it varied more (592, 542, 617, 631). In males aged 0–34 years, the incidence did not vary between the 4-year periods (p=0.63), but time changes among the 3-year age groups differed (ppp=0.08). For both sexes median age at diagnosis was higher in 1983–1986 than in 1995–1998 (pConclusion/interpretation. During a 16-year period the incidence of Type I diabetes did not increase in the 0–34 years age group in Sweden, while median age at diagnosis decreased. A shift to younger age at diagnosis seems to explain the increasing incidence of childhood Type I diabetes.