A new study published in theBritish Medical Journalshowed that diabetes mellitus (DM) and low BMI have negative influence on long-term survival in individuals with chronic total occlusion (CTO). One of the more difficult subtypes of coronary artery disease (CAD) is chronic complete occlusion. About one-fourth of individuals with chronic coronary syndrome and 16% to 30% of patients undergoing coronary angiography have CTO. Diabetes mellitus (DM), which is characterized by insulin resistance, β-cell dysfunction, and chronic hyperglycemia, is a primary contributor to vascular problems. Another important factor influencing cardiovascular outcomes in individuals with CAD is body mass index (BMI), as obesity is becoming much more common in the general population. Thus, this study assessed how body mass index (BMI) and diabetes mellitus affected the long-term all-cause mortality of patients with CTO. The Swedish Coronary Angiography and Angioplasty Registry was a part of this retrospective, countrywide cohort research, which ran from June 2015 to December 2021. 24,284 patients had CTO that was verified by angiography. Excluded is previous coronary artery bypass graft surgery. DM status and BMI classifications (underweight, healthy weight, overweight, and obesity) were used to create subgroups. A 31% increased risk of death was associated with DM, which was present in 30.3% of patients (HR: 1.31, 95% CI: 1.20 to 1.42; p<0.001). Diabetes patients who used insulin had a 52% higher risk (HR: 1.52; 95% CI: 1.38 to 1.67; p<0.001). BMI showed that the risk was lower for overweight (HR: 0.70, 95% CI: 0.64 to 0.77; p<0.001) and obese (HR: 0.74, 95% CI: 0.68 to 0.81; p<0.001) groups than for the healthy-weight group, while the risk was higher for underweight people (HR: 1.61, 95% CI: 1.25 to 2.08; p<0.001). An asymmetric U-shaped correlation was found using a continuous BMI spline: mortality increased sharply below 23 kg/m2, reached its lowest risk (nadir) at 32 kg/m2, and increased moderately beyond 35 kg/m2. Overall, insulin treatment further increased risk, and diabetes mellitus (DM) independently predicted higher long-term mortality in this national CTO population, along with more severe comorbidities and greater CTO complexity. The patients who were overweight or obese fared better, whereas those who were underweight fared the worst. Mohammed, M., Sundström, J., Louca, A., Hellsen, G., Rawshani, A., Olivecrona, G. K., Mohammad, M. A., Ioanes, D., Jensen, U., Erlinge, D., MD, PhD, Angerås, O., Petursson, P., Myredal, A., Völz, S., Dworeck, C., Odenstedt, J., Rawshani, A., & Råmunddal, T. (2025). Impact of diabetes mellitus and body mass index on long-term survival in chronic total occlusion patients: a nationwide cohort study from the SCAAR registry. BMJ Open, 15(9), e100074.https://doi.org/10.1136/bmjopen-2025-100074