ADULT-ONSET type 1 diabetes (T1D) is increasingly recognised as a distinct and clinically important condition, yet its long-term outcomes have been less well studied than childhood-onset T1D. In particular, limited data exist on prognosis and risk factors among individuals diagnosed with T1D after the age of 40. This population-based cohort study sought to evaluate the risks of major adverse cardiovascular events (MACE) and mortality among adults with newly diagnosed T1D, compared with both type 2 diabetes (T2D) and the general population. A key finding is that individuals with adult-onset T1D had a 71% higher risk of all-cause mortality compared to population controls.
The study drew on data from over 10,000 adults diagnosed with T1D and over 375,000 with T2D between 2001 and 2020, using Sweden’s National Diabetes Register and Total Population Register. These cohorts were followed until 2022, with outcomes including MACE and cause-specific mortality. Statistical analysis employed hazard ratios (HRs) and population attributable risk fractions (PAR%) to identify prognostic factors and quantify their impact.
Compared with population controls, people with adult-onset T1D had significantly increased rates of MACE (hazard ratio [HR] 1.30: 95% CI; 1.17–1.45) and all-cause mortality (HR: 1.71; 95% CI: 1.60–1.84). Compared to individuals with T2D, they had a lower risk of MACE (HR: 0.67; 95% CI: 0.60–0.75), but markedly higher mortality due to diabetic coma or ketoacidosis (HR 7.04; 95% CI: 4.54–10.9). The most influential risk factors for death in T1D were smoking (PAR% 10.7%) and HbA1c ≥53 mmol/mol (10.4%), while overweight or obesity (19.8%) was the strongest contributor to MACE. Findings were consistent among those diagnosed at age 40 or older, who also showed worse glycaemic control and lower insulin pump use.
These results highlight the substantial mortality and cardiovascular burden associated with adult-onset T1D, particularly in those diagnosed later in life. Despite lower MACE rates than in T2D, individuals with T1D face unique risks, including acute metabolic complications. The findings underscore the importance of improving glycaemic control, smoking cessation, and weight management as clinical priorities. Limitations include the observational nature of the study and potential misclassification between T1D and T2D, especially in older adults. Nonetheless, the study supports a more proactive and differentiated approach to managing adult-onset T1D in clinical practice.
Reference
Wei Y et al. Adult-onset type 1 diabetes: predictors of major cardiovascular events and mortality. Eur Heart J. 2025;DOI: 10.1093/eurheartj/ehaf304.
