Thyroid, Celiac, and Other Autoimmune Diseases and the Risk of Incident Type 1 Diabetes in Young Adulthood

<p dir="ltr">Objective: The association between autoimmune diseases and type 1 diabetes (T1D) is mostly based on studies among people with T1D at baseline. We assessed the risk of incident T1D among adolescents with other autoimmune diseases.</p><p dir="ltr">Research Design and Methods: Included were all Israeli adolescents without history of dysglycemia, aged 16-19 years, undergoing medical evaluation before mandatory military service between January 1996 and December 2016. Data were linked with information on adult-onset T1D from the Israeli National Diabetes Registry. The cohort was dichotomized by the presence of any autoimmune disease. Cox proportional hazards modeling was applied.</p><p dir="ltr">Results: A total of 1,426,362 people were included, of whom 38,766 [2.7%] had a history of autoimmunity at study entry (10,333 with autoimmune thyroid disease (AITD); 9,603 with celiac disease). Over 15,810,751 person-years of follow-up, there were 37 and 740 incident cases of T1D among people with and without autoimmunity, respectively, and crude incident rate of 9.6 and 4.8 case/105 person-years, respectively. In a multivariable model adjusted for sex, birth year, and socio-demographic variables the HR for incident T1D among people with autoimmunity was 2.19 (95%CI 1.57-3.04) vs. those without. Results persisted when islet-autoantibody data was used as mandatory criteria for T1D case definition (HR 2.22, 95%CI 1.13-4.35). The HRs among people with AITD and celiac disease were 3.99 (2.5-6.4) and 2.82 (1.46-5.45), respectively.</p><p dir="ltr">Conclusions: Autoimmune diseases in late adolescence were associated with an increased risk of T1D in adulthood in both sexes, especially among those with AITD and celiac disease.</p>