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 .
The impact of body mass index on short- and long-term outcomes inpatients undergoing coronary revascularization. Insights from the bypass angioplasty revascularization investigation (BARI).
OBJECTIVES We sought to investigate the impact of body mass index ( BMI ) on short- and long-term outcomes after initial revascularization with percutaneous transluminal coronary angioplasty ( PTCA ) or coronary artery bypass graft surgery ( CABG ) .  BACKGROUND Equivocal results exist on the impact of BMI on the risk of in-hospital complications after PTCA or CABG , and no long-term mortality data exist from a large series of revascularized patients . METHODS From the r and omized series and observational registry of the Bypass Angioplasty Revascularization Investigation ( BARI ) , 2,108 patients who had PTCA and 1,526 patients who had CABG were evaluated by taking their BMI at study entry . They were classified as follows : low ( < 20 kg/m(2 ) ) , normal ( 20 to 24.9 kg/m(2 ) ) , overweight ( 25 to 29.9 kg/m(2 ) ) , class I obese ( 30 to 34.9 kg/m(2 ) ) and class II/III obese ( greater-than-or-equal 35 kg/m(2 ) ) . In-hospital complications and short- and long-term mortalities were compared between levels of BMI within each mode of initial revascularization . RESULTS Among patients who had PTCA , each unit increase in BMI was associated with a 5.5 % lower adjusted risk of a major in-hospital event ( death , myocardial infa rct ion , stroke , coma ) ; among patients who had CABG , no difference in the in-hospital outcome was observed according to BMI . In contrast , BMI was not associated with five-year mortality in the PTCA group ; among the CABG group , adjusted relative risks of five-year cardiac mortality according to levels of BMI were 0.0 ( low ) , 1.0 ( normal ) , 2.02 ( overweight ) , 3.16 ( class I obese ) and 4.85 ( class II/III obese ) ( linear p < 0.001 ) . CONCLUSIONS Body mass index appears to have a differential impact on short- and long-term outcomes after coronary revascularization . These results underscore the need for further research to identify factors responsible for the apparent short-term protective effect of a higher BMI in patients undergoing PTCA and to study the impact of weight reduction on the long-term survival of obese patients undergoing CABG
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 .