Gender bias: Stroke after heart surgery.

Women undergoing heart surgery are more likely to die than men are. This trend is typically blamed on the fact that women with heart problems tend to be older and sicker than men with heart disease. However, a new study suggests that even after accounting for these differences, women are more likely than men are to die of stroke after heart surgery.

Among a sample of about 400,000 people in the United States who had heart surgery during 1996 and 1997, 5.7 percent of the women died within a month after surgery, but only 3.5 percent of the men did.

While 3.8 percent of women suffered a stroke or coma after surgery, only 2.4 percent of men did, the study found. As a group, these patients had a much higher chance of dying within a month of their surgery: 32 percent of the women and 28 percent of the men died.

After accounting for all known risk factors for stroke, women had a 21 percent higher chance of developing a stroke than men did, says study author Charles W. Hogue of the Washington University School of Medicine in St. Louis. Hogue and his colleagues report their results in the May 1 CIRCULATION.

It remains unclear why women are more likely to develop stroke than men are, Hogue says. He speculates that the female sex hormone estrogen might play a role.

"Stroke is potentially preventable," says Hogue. "If we can develop better ways of reducing stroke after surgery, we may be able to improve outcomes."