Now, a new University of Michigan study suggests that the answer to the mystery may lie with infections, regardless of their location in the body.
In a paper in the Archives of Internal Medicine, U-M Health System researchers report that 96 percent of the gender difference in death risk within 100 days of coronary artery bypass surgery may be explained by differences in infection. They used hospital and post-hospital data from 9,218 Michigan residents who had bypass surgery in a 15-month period. All were Medicare beneficiaries age 65 years or older.
"Overall, we found that women's increased risk of mortality after coronary artery bypass surgery may be due to differences in infection," says lead author Mary A. M. Rogers, Ph.D., M.S., research director of the Patient Safety Enhancement Program of the U-M Health System and the Veterans Affairs Ann Arbor Healthcare Center. "We found that 16 percent of women patients had an infection, compared with 10 percent of men." This difference persisted after taking into account age, race, urgency of the operation, length of hospital stay, most co-existing medical conditions, and the number of bypass operations performed at each hospital or by each surgeon.
"We suspect that there may be a systemic, or body-wide, response to infection, making infection at any site a concern in elderly patients," Rogers continues. She notes that women in the study were more likely than men to have infections of the urinary, respiratory and digestive tracts. Women were also more likely than men to have skin and post-operative infections.