Decreased Incidence of Type 1 Diabetes in Young Finnish Children
OBJECTIVE <p>The incidence of type 1 diabetes has been rising for decades, particularly among young children. Between 2006 and 2011 the incidence rate reached a plateau in Finland. In this observational register-based cohort study, we assess recent trends in the disease rate in Finnish children.</p> <p>RESEARCH DESIGN AND METHODS</p> <p>Based on data from the Finnish Pediatric Diabetes Register, we studied the incidence of type 1 diabetes among children under the age of 15 years between 2003 and 2018. We assessed sex-specific incidence rates (IRs) per 100,000 person years (PY) by 4-year time periods in three age groups (0.50–4.99, 5.00–9.99, and 10.00–14.99 years).</p> <p>RESULTS</p> <p>Among the 7,871 children with newly diagnosed type 1 diabetes, the median age at diagnosis increased from 7.88 to 8.33 (<i>P </i>= 0.001), while the overall IR decreased from 57.9/100,000 PY in 2003–2006 to 52.2/100,000 PY in 2015–2018, yielding an IR ratio (IRR) of 0.90 (95% CI 0.85–0.96, <i>P </i>= 0.001). This decline was mainly due to the decrease in the youngest age group [IRR 0.77 (95% CI 0.68–0.87); <i>P </i>< 0.001], being significant both among males and females. In the middle age group, a significant decrease was observed only among females. No changes were observed in the oldest children.</p> <p>CONCLUSIONS</p> <p>The incidence of type 1 diabetes decreased among young Finnish children between 2003 and 2018. Current findings imply that environmental factors driving the immune system towards islet autoimmunity are changing in young children.</p>