To evaluate the effects of diabetes mellitus (DM) and body mass index (BMI) on long-term all-cause mortality in chronic total occlusion (CTO) patients.

Retrospective, nationwide cohort study.

Swedish Coronary Angiography and Angioplasty Registry, between June 2015 and December 2021.

24 284 patients with angiographically confirmed CTO. Prior coronary artery bypass graft surgery excluded. Subgroups were defined by DM status and BMI categories (underweight, healthy weight, overweight, obesity).

Long-term all-cause mortality, assessed by Kaplan-Meier analysis and multivariable Cox proportional hazards regression.

DM was present in 30.3% of patients and conferred a 31% higher risk of mortality (HR: 1.31, 95% CI: 1.20 to 1.42; p2, lowest risk (nadir) at 32 kg/m² and modest rise above 35 kg/m².

In this nationwide CTO cohort, DM independently predicted higher long-term mortality, accompanied by more severe comorbidities and greater CTO complexity, and insulin therapy further elevated hazard. Overweight and obese patients had better survival, while underweight individuals had the poorest prognosis. These findings underscore the importance of individualised risk assessment and management strategies in CTO patients, particularly those with DM or low BMI.