Autoimmune disorders in adolescence may signal a higher lifetime risk of T1D, according to a large population-based cohort study published in Diabetes Care. The study followed more than 1.4 million adolescents aged 16 to 19 years who were free of dysglycemia at baseline and underwent long-term health monitoring.
Within the cohort, 2.7% had a documented autoimmune condition, most commonly AITD or celiac disease.

Over 15.8 million person-years of follow-up, 37 participants with autoimmunity and 740 without developed T1D. After adjusting for sex, birth year, and sociodemographic factors, those with autoimmune disease had a 2.19-fold higher risk of developing T1D (95% confidence interval [CI] 1.57–3.04). The association remained robust when islet autoantibody data were included in the T1D case definition (HR 2.22, 95% CI 1.13–4.35).

Adolescents with AITD and celiac disease showed the strongest associations, with hazard ratios of 3.99 (95% CI 2.5–6.4) and 2.82 (95% CI 1.46–5.45), respectively. The elevated risk was observed across both sexes and persisted into adulthood.

These results indicate that autoimmune conditions in late adolescence are significant predictors of future T1D. Incorporating autoimmune screening into preventive strategies could help identify high-risk individuals earlier and enable closer metabolic surveillance.