Parental education and occupation in relation to childhood type 1 diabetes: nationwide cohort study

Background Socioeconomic status in the risk of developing type 1 diabetes seems inconsistent. We investigated whether risk of childhood-onset type 1 diabetes differed by parental education or occupation in a nationwide cohort. Methods This cohort study included all children born in Norway from 1974 to 2013. In individually linked data from nationwide population registries following children born in Norway up to 15 years of age, we identified 4647 with newly diagnosed type 1 diabetes during 15 381 923 person-years of follow-up. Results Children of mothers with a master’s degree had lower risk of type 1 diabetes than children of mothers with completed upper secondary education only (adjusted incidence rate ratio, aIRR=0.82 95% CI: 0.70 to 0.95). There was no difference between upper secondary and lower secondary maternal education (aIRR=0.98, 95% CI: 0.89 to 1.08). Paternal education was not significantly associated with type 1 diabetes, lower secondary compared with upper secondary aIRR 0.96 (0.88–1.05) and master compared with upper secondary aIRR 0.93 (0.83–1.05). While maternal elementary occupation was associated with a lower risk of type 1 diabetes, specific maternal or paternal occupations were not. Conclusions Our results suggested inverse U-shaped associations between maternal socioeconomic status and risk of type 1 diabetes. Non-linear associations may be part of the reason why previous literature has been inconsistent.