MONDAY, Feb. 27, 2006 (HealthDay News) -- An increased incidence of infection may explain why women are more likely than men to die days or weeks after having heart bypass surgery.
In fact, researchers at the University of Michigan say 96 percent of the gender gap in death risk within 100 days of coronary artery bypass surgery may be explained by differences in infection rates.
Another expert said there may still be more to the story, however.
"This is very important, but this is maybe one of several factors," said Dr. Nieca Goldberg, chief of women's cardiac care at Lenox Hill Hospital in New York City. "Previous studies have shown that women coming to bypass are sicker than men and have other coexisting medical conditions such as diabetes and hypertension that can contribute to increased complications."
According to the study, published in the Feb. 27 issue of the Archives of Internal Medicine, bypass surgery is one of the most common surgeries in the United States, with more than half a million procedures performed every year.
While it's well known that women are more likely to die after the procedure, explanations for this gender gap remain controversial.
Possible explanations include females' smaller arteries, along with a greater likelihood for other preexisting conditions.
The role of infection, however, had not been explored -- even though chronic infection is associated with atherogenesis, or the build-up of plaque along the artery walls.
In this study, the researchers analyzed hospital and post-hospital data from more than 9,200 Michigan Medicare beneficiaries who had undergone bypass surgery during a 15-month period.
Just over 16 percent of women hospitalized for bypass surgery had an infection vs. 9.8 percent of men, the team found.
Respiratory tract, urinary tract, digestive tract and skin and subcutaneous tissue infections were more common in women than in men.
About 12 percent of patients who had infections while in the hospital died before being discharged, compared with 4 percent of those without infections.
However, "once infected, men were more likely to die than women," said study author Mary A. M. Rogers, research director of the Patient Safety Enhancement Program at the University of Michigan Health System and Veterans Affairs Ann Arbor Healthcare Center.
According to the study, men with infections had a threefold increased risk of death compared to uninfected men. In contrast, women who contracted an infection after their surgery were 1.8 times more likely to die than women who did not develop an infection.
That finding was surprising at first, Rogers said, but may be related to the overall survival advantage that women enjoy.
As to why women have an higher incidence of infection, the authors can only speculate.
Women are more likely than men to have diabetes, which is a risk factor for infection. Good control of blood sugar after surgery, in particular, has been shown to reduce the chance of infection.
Women are also more likely to have immune-related disorders such as lupus and arthritis, and the use of immunosuppressant therapy or corticosteroids increase the risk of infection.
Perhaps the more pertinent point is that hospitals already have guidelines in place, which, if followed, should reduce this burden.
"We have recommendations for infection control," Rogers said. "It's a problem of putting into practice these procedures on a daily basis."
Guidelines include administering antibiotics one hour prior to incision, yet one recent study showed that this actually occurred only about 55 percent of the time, Rogers said.
There are also things women (and men) can do to minimize the risk of infection.
Elderly people should get annual flu vaccines and, every five years, vaccines for bacterial pneumonia (pneumococcal vaccine). According to Rogers, only two-thirds of elderly people actually get their influenza vaccination and only about half receive their pneumococcal vaccine on schedule. Health-care workers who take care of these patients are also undervaccinated.
In the hospital, patients should start to walk as soon as possible after the operation and should also wash their hands frequently, to cut down on infection risk.
More information
For more on women and cardiovascular disease, head to the American Heart Association.
