Incidence of Insulin-Dependent Diabetes Mellitus among Children in a North-Swedish Population 1938–1977

Abstract

Insulin-dependent diabetes mellitus (IDDM) was studied retrospectively in children 0–14 years of age registered at a northern Swedish department of Paediatrics. In the years 1938–77, the new cases of IDDM registered were 307. The mean yearly incidences were 14.2 cases per 100,000 during 1938–42 and 37.9 cases per 100,000 during 1973–77. The lowest incidende rate of 10.2 per 100,000 was seen during the wartime, 1940–45. To investigate the changing age distribution, directly standardized rate ratios (SRR) were calculated for 4 ten-year periods. Significantly lower incidence (SRR = 73) was observed during the first period 1938–47 and significantly higher (SRR = 137) for the last period 1968–77 as compared to the whole period (SRR = 100). The increasing incidence during the last decade was especially marked for children below 5 years of age. The geographic variation between 11 community areas was measured by the indirectly standardized morbidity ratios (SMR) showing a range between 40 and 179. Peak incidences of new cases were seen during winter and summertime. The current (31 December 1977) prevalence of IDDM among children 0–14 years of age in Västerbotten was 3.0 per 1,000. Our study suggests that the incidence of insulin-dependent diabetes among children has been increasing since 1938.