Incidence, seasonal and geographical patterns of juvenile-onset insulin-dependent diabetes mellitus in Denmark.

The incidence, sex, seasonal and geographical patterns of juvenile-onset insulin-dependent diabetes mellitus (j.i.d.m.) were studied retrospectively on one third of the Danish population 1970-1974. The j.i.d.m. incidence remained fairly constant during the study period, the average being 13.2 per 100000 per year. The total number of boys exceeded the number of girls by 27%. A marked peak of incidence was found at 12-14 years, earlier for females than for males. A seasonal variation in onset (diagnosis) of j.i.d.m. was observed with the lowest number of new cases in May-July. The j.i.d.m. incidence seemed to show socioeconomic differences, being highest in those parts of the survey area with lower status.