Why are mortality rates following coronary artery bypass graft (CABG) surgery higher for women than men? Higher infection rates among women may help explain the discrepancy.

Researchers analyzed clinical outcomes of 9,218 patients age 65 and older who had CABG surgery. Mortality rates in the 100 days after surgery were 9.2% for women and 6.4% for men.

Sixteen percent of the women had an infection during their hospital stay, compared with just under 10% of men. Common infection sites included the urinary, respiratory, and gastrointestinal systems, and the skin and subcutaneous tissue. The higher infection rates for women held true regardless of such factors as age, race, and concurrent conditions.

Being female carried a 13.9% mortality risk. But after researchers adjusted the data for infection, the mortality risk for women decreased to 0.3%.

Researchers can't say what accounts for higher infection rates among women. Possibilities include differences in glucose control in those with diabetes and a higher prevalence of immune-related disorders, leading to greater use of immunosuppressive drugs. Genetic differences in immune and inflammatory responses may also contribute to different infection rates between the sexes.

Researchers stress the importance of strictly adhering to infection control guidelines. These include administering prophylactic antibiotics within 1 hour before making a surgical incision and vaccinating health care workers and patients against influenza.

Sources: Contribution of infection to increased mortality in women after cardiac surgery, Archives of Internal Medicine, M Rogers, et al., February 27, 2006.