Increasing trends in the incidence and prevalence rates of type 1 diabetes among children and adolescents in the Netherlands.

Objective: To assess the trends in the incidence and prevalence rates of type 1 diabetes (T1D) among children and adolescents in the Netherlands.

Methods: A population-based cohort study was conducted in the Dutch PHARMO record linkage system (1998-2011). All children and adolescents aged ≤19 yr with at least one insulin dispensing (as a proxy for T1D) were identified and the numbers of incident and prevalent cases (numerators) were calculated. Overall age-adjusted (0-19 yr) incidence and prevalence rates together with age- and sex-specific rates of T1D and their 95% confidence intervals (CI) were calculated using data from the Dutch Central Bureau of Statistics as denominator. Trends over time were assessed using Joinpoint regression software (National Cancer Institute, Bethesda, MD, USA).

Results: In 2011, the overall age-adjusted incidence and prevalence rates of T1D were 25.2/100 000 (95% CI, 23.7-26.8) person-years (PY) and 174.4/100 000 (95% CI, 170.2-178.5) children, respectively. The average annual percentage change (AAPC) in the overall age-adjusted incidence and prevalence rate was 3.7% (95% CI, 1.8-5.7) and 3.8% (95% CI, 2.4-5.2), respectively. While during the study period the largest increases in the incidence and prevalence rates of T1D were observed for the oldest age groups (10-14 and 15-19 yr), a decreasing trend was detected for the 0- to 4-yr-old category (with AAPCs of -1.8 (95% CI, -9.9 to 7.1) and -6.9% (95% CI, -11.5 to -2.1) for incidence and prevalence, respectively).

Conclusion: Age-adjusted incidence (1999-2011) and prevalence rates (1998-2011) of T1D in Dutch children (aged 0-19 yr) continued to increase and a shift was observed to a later onset of the disease.