Increasing Contribution of Adolescent Type 1 Diabetes Drives Incidence Rates in Poland - a 40-year-long Observational Study.

Background: The incidence of childhood type 1 diabetes (T1D) has increased globally in recent decades. Analyzing incidence trends can elucidate patterns and predict future healthcare burdens. We aim to assess changes in the incidence and prevalence of pediatric type 1 diabetes over 40 years in Central Poland.

Methods: This prospective observational study in Lodz Province registered all new-onset type 1 diabetes cases in children 0-14 years old admitted from 1983 to 2022 to reference centres for pediatric diabetes. Diagnoses were based on established guidelines, and other types of diabetes were excluded. Population data were obtained from Poland's General Statistical Office.

Results: The incidence rate of type 1 diabetes increased tenfold, from 3.29/100,000 (95%CI: 1.85-4.73) in 1983 to 32.43 (26.42-38.44) in 2022, with an annual percentage change of 5.73% (4.99%-6.44%) and two distinct increase periods: rapid in 1983-2005 (7.38% [6.30-10.52%]) and slower in 2005-2022 (3.65% [-0.86-5.13%]). Incidence rates in 0-4-year-olds were significantly lower than in 5-9 and 10-14-year-olds. (p<0.0001). While incidence plateaued in the 0-4-year-olds after 2007, it consistently increased in older children. Most new cases were diagnosed in winter (December-February, a mean difference from the remaining seasons of 29±11.6% points, p<0.0001). The prevalence of type 1 diabetes increased, reaching 177.21/100,000 (163.18-191.24) in 2022.

Conclusions: Over the past 40 years, the incidence of pediatric type 1 diabetes in Central Poland has increased significantly, though the rate is slowing. Most new cases occur in children 10 years old and older, so healthcare systems should adapt to young adults who are extensive users of new diabetes technologies.