Incidence of Type 1 diabetes mellitus and effect on mortality in young patients with congenital heart defect - A nationwide cohort study

Background: 1% of all live born children are born with a congenital heart defect (CHD) and currently 95% reach adulthood. Type 1 diabetes mellitus (T1DM) is an autoimmune disease that can develop due to i.e. heredity, exposure to infections and stress-strain. The incidence of T1DM in patients with CHD is unknown and we analysed the risk of developing T1DM for patients with CHD, and how this influences mortality.

Methods: By combining registries, the incidence of T1DM and the mortality was analysed in patients with CHD by birth cohort (1970-1993, 1970-1984 and 1984-1993) matched with population-based controls matched for sex, county and year of birth without CHD and followed from birth until a maximum of 42 years.

Results: 221 patients with T1DM among 21,982 patients with CHD and 1553 patients with T1DM among 219,816 matched controls were identified. The hazard ratio (HR) for developing T1DM was 1.50 (95%, CI 1.31-1.73) in patients with CHD compared to the controls and the first birth cohort (1970-1984) had the highest risk for T1DM, HR 1.87 (95%, CI 1.56-2.24). After onset, mortality risk was 4.21 times higher (95%, CI 2.40-7.37) in patients with CHD and T1DM compared to controls with T1DM.

Conclusion: From a nationwide cohort of patients with CHD and controls, the incidence of developing T1DM was 50% higher in patients with CHD, showing a significant increase in risk among birth cohort 1970-1984. The combination of CHD and T1DM was associated with a 4-fold increase in mortality compared to controls with only T1DM.