Parental Autoimmune Disease and Offspring Type 1 Diabetes in Sweden

Researchers used Swedish national health registers to follow children born from 2001 through 2014, from birth until type 1 diabetes (T1D), death, emigration, or the end of 2023. The cohort included 1,455,645 children, followed for a median of 15.3 years. Parental autoimmune diseases diagnosed before or during pregnancy were assessed in relation to incident T1D using Cox regression; maternal and paternal associations were compared, with cousin analyses used to examine shared familial factors.

During follow-up, 10,273 children (0.71%) developed T1D. Maternal autoimmune disease during pregnancy was associated with higher offspring risk (adjusted hazard ratio [HR], 1.57; 95% CI, 1.46-1.68), as was paternal autoimmune disease before childbirth (HR, 1.51; 95% CI, 1.37-1.67). The overall maternal-to-paternal HR ratio was 1.04 (95% CI, 0.92-1.17), showing no overall difference. In cousin analyses, the maternal association was attenuated but persisted (HR, 1.27; 95% CI, 1.08-1.50).

The findings point to shared familial susceptibility as a likely contributor, while leaving open possible intrauterine effects for particular diseases. The observational design cannot establish causation, and the reported associations do not establish a basis for changes to clinical care.