Sex differences in hospital mortality after coronary artery bypass surgery: evidence for a higher mortality in younger women.

BACKGROUND: Data are conflicting over whether women have higher mortality than men after coronary artery bypass graft (CABG) surgery. Younger but not older women hospitalized for acute myocardial infarction have higher in-hospital mortality rates than men. We hypothesized that younger women also have higher in-hospital mortality rates after CABG. METHODS AND
RESULTS: We studied 51 187 patients (30% women) included in the National Cardiovascular Network database who received CABG at 23 clinical centers between October 1993 and December 1999. Compared with men, fewer women were white and more women had risk factors and comorbidities. These differences were more apparent in younger patients. In all age groups, however, women had higher left ventricular ejection fraction and fewer diseased vessels. Women had higher in-hospital mortality rates than men, but sex differences in mortality were more marked among younger patients. Women <50 years of age were 3 times more likely to die than men (3.4% versus 1.1%), and women 50 to 59 years of age were 2.4 times more likely to die than men (2.6% versus 1.1%). In the older age categories, the sex difference in in-hospital mortality was less marked (P<0.001 for the interaction between sex and age). Adjustment for preoperative risk factors only slightly decreased the strength of this interaction.
CONCLUSIONS: Younger women undergoing CABG surgery are at a higher risk of in-hospital death than men, but this difference in risk decreases with advancing age. Additional investigation is needed to determine why in-hospital mortality is higher in women after CABG, with particular focus on younger women.