Conclusions : Obesity is associated with lower risks after cardiac surgery , with consistent effects noted in multiple analyses attempting to address residual confounding and reverse causation
Background : In an apparent paradox , morbidity and mortality are lower in obese patients undergoing cardiac surgery  , although the nature of this association is unclear .
We sought to determine whether the obesity paradox observed in cardiac surgery is attributable to reverse epidemiology , bias , or confounding .
Obesity paradox in coronary artery bypass grafting: myth or reality?
OBJECTIVE A high body mass index has been suggested to be protective in patients with coronary artery disease and in those undergoing coronary artery bypass grafting ( CABG ) .  However , these conflicting results might be related to the different risk profiles among the various body mass index categories . We sought to clarify the effect of varying degrees of excessive body weight on hard clinical outcomes in patients undergoing CABG .  METHODS A retrospective analysis of prospect ively collected data was conducted to investigate the effect of a high body mass index on early and late mortality after  first-time isolated CABG . Propensity score matching was used to adjust for confounding factors . RESULTS The study sample consisted of 3269 normal weight , 6662 overweight , 3821 obese , and 211 morbidly obese patients . After matching , early mortality was not affected by overweight ( mean difference , 0.7 % ; 95 % confidence interval [ CI ] , -0.2 % to 1.5 % ) , obesity ( mean difference , 0.5 % ; 95 % CI , -0.7 % to 1.7 % ) , and morbid obesity ( mean difference , 1.6 % ; 95 % CI , -1.0 % to 1.0 % ) , regardless of the patients ' risk profile according to the European system for cardiac operative risk evaluation . Overweight status was not protective for late death ( hazard ratio , 1.05 ; 95 % CI , 0.9 - 1.08 ; P = .4 ) . Compared with normal weight patients , both obese and morbidly obese patients had a higher risk of late death ( hazard ratio , 1.22 ; 95 % CI , 1.07 - 2.66 ; P = .006 for obese patients ; hazard ratio , 1.36 ; 95 % CI , 0.74 - 2.49 ; P = .3 for morbidly obese patients ) . CONCLUSIONS Obesity did not increase operative mortality , but it was associated with reduced late survival in patients undergoing primary isolated CABG . Our results raise concerns in supporting any protective effect of obesity in cardiovascular disease , specifically in patients undergoing surgical myocardial revascularization
Conclusions : Obesity is associated with lower risks after cardiac surgery , with consistent effects noted in multiple analyses attempting to address residual confounding and reverse causation
Background : In an apparent paradox , morbidity and mortality are lower in obese patients undergoing cardiac surgery  , although the nature of this association is unclear .
We sought to determine whether the obesity paradox observed in cardiac surgery is attributable to reverse epidemiology , bias , or confounding .