Is it gender, methodology, or something else?

See related articles on pages 929, 936, 950, and 959. Are Outcomes Different? The thesis that women are different from men is not argued in any more important venue than the surgical theatre. The questions of whether and why women have higher probabilities of poor outcomes after coronary artery bypass grafting (CABG) have been repeatedly asked. A common denominator among published investigations is that the preoperative profile of the female patient is vastly different from that of the male patient. Some risk factors traditionally associated with increased morbidity and mortality after CABG are more commonly represented in the preoperative profile of the female patient. The extent to which these factors explain gender differences, however, varies among studies. Some investigations report higher adjusted mortality for women, whereas others, with application of adjustment strategies, report similar in-hospital mortality between women and men, and yet others report similar postoperative mortality for women and men despite differences in baseline characteristics. How can multiple studies examining the role of gender in surgical outcomes lead to such varied conclusions despite similar analyses of observational databases? If one structures the question correctly, collects the necessary data, and performs the appropriate analysis, one should expect a consistent answer. On the subject of gender, is the question structured to be answered, is there some unmeasured or unknown biologic variable or process-of-care decision in the perioperative period that is influencing outcomes, or is it the variable application of statistical methodology?