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Higher rates of infection may explain why women have higher risk of death after bypass surgery

February 28, 2006

Higher rates of infection among women undergoing coronary artery bypass surgery may explain why women have higher risk of death than men following the procedure, according to a study in the February 27 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.

More than half a million coronary artery bypass graft (CABG) surgeries are performed in the United States every year, making it one of the most common surgical procedures in the country, according to background information in the article. Physicians know that women who undergo the procedure are more likely to die during hospitalization than men. This may be because of differences in artery size or the higher rate of other diseases and conditions among women, though these explanations remain controversial.

Mary A.M. Rogers, Ph.D., of the University of Michigan, Ann Arbor, and colleagues hypothesized that part of the disparity may be explained by gender differences in infection rates and consequences. They studied a group of 9,218 Medicare beneficiaries (5,749 men and 3,469 women) in Michigan who underwent CABG surgery between July 1997 and September 1998. Of these participants, 1,122 (12.2 percent) had an infection during their hospitalization.

The researchers found that women were significantly more likely to develop infection than men (16.1 percent vs. 9.8 percent), even when considering other factors such as age, length of stay, type of admission, race and presence of other illnesses. Urinary, digestive, respiratory and skin and subcutaneous (under the skin) tissue infections were all more common in women than men. More patients with infections died in the hospital (11.9 percent) than did those without infection (4 percent), and these higher mortality rates continued throughout the 100-day follow-up. The relationship between infection and death was stronger in men than in women-men with an infection were three times as likely to die as men without, while infected women had an increased risk of 1.8 times that of uninfected women.

"Clearly, infection is an important factor when evaluating the association between sex and mortality after CABG surgery," they conclude. "As a direct indicator of patient safety, infection at any site, regardless of time of onset, warrants additional investigation as a potential contributor to mortality."

JAMA and Archives Journals