Incidence of childhood‐onset type 1 diabetes in Biscay, Spain, 1990–2013

Objective To identify the incidence rate (IR) and epidemiologic trends of childhood type 1 diabetes mellitus (T1DM) in children aged 0 to 14‐yr‐old from 1990 to 2013, in the north of Spain (Biscay). Subjects and Methods A prospective‐retrospective study was performed. Capture–recapture method was used: primary cases were ascertained from hospital register and a secondary independent data source was obtained from diabetes associations and public health plan database. Age and sex‐standardized incidence rates were calculated using direct method, assuming an equal distribution in each age/sex group. In order to identify and analyse trends the period studied was divided into two (1990–2001 and 2002–2013) 11‐year periods. The 95% confidence interval (CI) was estimated assuming the Poisson distribution. Results A total of 399 new cases were identified throughout the study. Mean age at diagnosis was 8.9 ± 3.7 yr. Completeness of ascertainment was 99.1%. Mean annual age‐standardized IR was 10.7 (95% CI: 9.6–11.7). The mean incidence for the 0–4, 5–9 and 10–14 age groups was 5.1, 14.6 and 13.2 per 100,000 children/yr, respectively. The incidence rate trend in the whole group was not statistically significant. In the 10–14 age group we found a yearly average increase (2.5% [CI 95% 0.4–4.6]; P < 0.05) and analysing by sex, this statistically significant incidence trend was observed only in boys. We did not find a seasonal onset pattern. Conclusions The IR did not increase in this population during the period studied unlike the results in other Spanish regions and European Countries.