Influence of diabetes and obesity on ten-year outcomes after coronary artery bypass grafting in the arterial revascularisation trial.

Aims: Diabetes and obesity are common conditions which can influence outcomes after coronary artery bypass graft (CABG) surgery. The aim of this study was to evaluate the influence of diabetes and obesity, and their interactions, on ten-year outcomes following CABG.

Methods and results: Patients enrolled in the Arterial Revascularisation Trial (ART) were stratified by diabetes and obesity at baseline. Diabetes was further stratified into insulin and non-insulin dependent. The primary outcome was all-cause mortality at 10 years of follow-up. Secondary outcomes were the composite of all-cause mortality, myocardial infarction or stroke at 10 years, and sternal wound complications at 6 months follow-up. A total of 3096 patients were included in the analysis (24% with diabetes, 30% with obesity). Patients in the "diabetes/no obesity" group had a higher risk of all-cause mortality following CABG (adjusted hazard ratio [aHR] 1.33, 95% confidence interval [CI] 1.08-1.64, p = 0.01) compared to the reference group of "no diabetes/no obesity". No excess risk was observed in the "no diabetes/obesity" or "diabetes/obesity" groups. Patients with insulin dependent diabetes had a significantly higher ten-year mortality risk compared to no diabetes (aHR 1.85, 95% CI 1.41-2.44, p = 0.00). Patients in the "diabetes/no obesity" and "diabetes/obesity groups" had a higher risk of sternal wound complications (HR 2.29, 95% CI 1.39-3.79, p < 0.001 and HR 3.21, 95% CI 1.89-5.45, p < 0.001 respectively). The composite outcome results were consistent with the mortality results.

Conclusion: Diabetes, especially insulin dependent diabetes, is associated with a higher ten-year mortality risk after CABG, in contrast to obesity which does not appear to increase long term mortality compared to non-obese. The interaction between diabetes and obesity shows an apparent "protective" effect of obesity irrespective of diabetes on mortality. Both conditions are associated with a higher risk of post-operative sternal wound infections.