Association of Age at Type 1 Diabetes Onset With Survival, Cardiovascular, and Kidney Outcomes: A Nationwide Cohort Study

OBJECTIVE: To investigate the association of age at type 1 diabetes diagnosis with incident mortality, cardiovascular, and kidney outcomes. RESEARCH DESIGN AND METHODS: In this retrospective cohort study, individuals ≥18 years of age with type 1 diabetes with one or more entries in the Swedish National Diabetes Register (from January 1998 to December 2019) were followed from the date of first registration up to December 2020. Cox proportional hazards models were used to examine risk per 1-year increase in age at type 1 diabetes diagnosis and excess risk relative to comparator individuals from the Swedish Total Population Register. RESULTS: Cohorts consisted of 34,155 individuals with type 1 diabetes and 150,026 comparator individuals. The hazard ratio (HR) per 1-year increase in age at type 1 diabetes diagnosis was 0.98 (95% CI 0.98, 0.99) for all-cause mortality, indicating a 1.7% lower probability per 1-year increase in age at type 1 diabetes diagnosis (8.2% lower probability per 5-year increase). Corresponding HRs per 1-year increase in age at diagnosis were 0.97 (0.97, 0.98) for cardiovascular mortality and 0.99 (0.98, 0.99) for noncardiovascular mortality. Excess risk relative to comparator individuals was greatest when type 1 diabetes diagnosis occurred from 0 to 10 years of age, with HRs of 3.23 (2.92, 3.58) for all-cause mortality, 5.73 (4.32, 7.59) for cardiovascular mortality, and 3.01 (2.70, 3.36) for noncardiovascular mortality. CONCLUSIONS: Younger age at type 1 diabetes diagnosis is associated with greater risk of mortality and complications, with each additional year delay in onset being significantly associated with lower risk.