Time Trends, Regional Variability and Seasonality Regarding the Incidence of Type 1 Diabetes Mellitus in Romanian Children Aged 0-14 Years, Between 1996 and 2015

Objective: The incidence of type 1 diabetes mellitus in children is highly variable in the world. The aim of our study was to: 1) analyze the evolution of the incidence of childhood type 1 diabetes in Romania between 1996 and 2015, and: 2) to search for differences amongst age groups, gender, geographic regions and month of diagnosis.
Methods: Data on all new cases of type 1 diabetes, aged <15 years, obtained from two independent sources, were included in the study. The statistical methods included modeling of the incidence rates, adjusting for age, sex, calendar year, geographic region and seasonality.
Results: The study group was composed of 5422 children, with overall completeness of ascertainment estimated at 93.7%. The incidence rate (per 100.000 person-years) rose continuously, from 4.7 [95% confidence interval (CI) 3.9-5.7] in 1996 to 11.0 (95% CI 9.9-12.2) in 2015, by a yearly rate of 5.1%, highest in the youngest and lowest in the oldest children. The mean incidence was significantly higher (p<0.0001) in Transylvania (7.9, 95% CI 7.6-8.3) than in Moldavia (6.5, 95% CI 6.2-6.9) and Muntenia (7.0, 95% CI 6.7-7.3), probably due to differences regarding ethnicity and lifestyle. The monthly incidence showed a sinusoidal pattern, peaking in January and being minimum in June.
Conclusion: The incidence of type 1 diabetes mellitus in Romanian children increased continuously during the study period by a rate that, if maintained, would lead to its doubling every 14 years. Important differences were established between geographic regions and seasonality at diagnosis.