Evaluating The Joint Effect Of Body Mass Index And Diabetes With Late-Mortality After Coronary Artery Bypass Grafting

Abstract Introduction Survival analyses following coronary artery bypass grafting (CABG) evaluate the independent effects of body mass index (BMI) and diabetes. However, BMI and diabetes are correlated and their combined effects should be considered, thus we examined the joint association on long-term survival after CABG. Method A total of 15129 patients undergoing isolated CABG between 1997 and 2017 were analysed. The BMI categories were defined as Normal-Weight (≥18-<25 kg/m2;n=3783), Overweight (≥25-<30 kg/m2;n=7103), Class-I-Obese (≥30-<35kg/m2;n=3247), and Class-II-Obese (≥35 kg/m2;n=996). Diabetes was defined as ever having a diagnosis of diabetes (n=3203). The association was assessed using Cox-proportional hazards regression models. Result During follow-up, 3140 deaths occurred. Compared to Normal-Weight individuals, the multivariable-adjusted hazard ratios (HR) were 0.89 [95%CI: 0.82-0.96], 0.95 [95%CI: 0.86-1.10], and 1.30 [95%CI: 1.07-1.47] for Overweight, Class-I-Obese, and Class-II-Obese patients, respectively. Compared to non-diabetic patients, the multivariable-adjusted HR for diabetic patients was 1.55 [95%CI: 1.43-1.68]. In the joint analysis, compared to Normal-Weight non-diabetic individuals, the multivariable-adjusted HRs were: Normal-Weight diabetic 1.30 [95%CI: 1.10-1.53], Overweight non-diabetic 0.86 [95%CI: 0.78-0.94], Overweight diabetic 1.32 [95%CI: 1.16-1.50], Class-I-Obese non-diabetic 0.87 [95%CI: 0.77-0.99], Class-I-Obese diabetic 1.58 [95%CI: 1.53-1.85], Class-II-Obese non-diabetic 1.11 [95%CI: 0.90-1.38], and Class-II-Obese diabetic 2.06 [95%CI: 1.65-2.56]. The reduction in multivariable-adjusted 10-year survival rates for diabetics versus non-diabetics was 4%, 6%, 9%, and 14% for Normal-Weight, Overweight, Class-I-Obese, and Class-II-Obese, respectively. Conclusion A considerable difference in survival after CABG is seen in the joint analysis of diabetes and BMI and should therefore be considered in future studies. Take-home message Diabetes and body mass index (BMI) are both correlated with the incidence of coronary artery disease and the need for coronary artery bypass grafting (CABG) and are often statistically analysed as separate entities. We show that the joint affect of diabetes and BMI has a significantly higher risk of late-mortality following CABG, therefore such analyses should be considered in future studies.