Posted on 03/07/2005 2:15:18 PM PST by nickcarraway
Regular use of low-dose aspirin does not prevent first heart attacks in women, as it does in men, a 10-year study of healthy women has found. The nearly 20,000 women in the Women's Health Study who took 100 milligrams of aspirin every other day were no less likely to suffer a heart attack than a like-sized group of women who took placebos.
Aspirin did appear to help protect the women against stroke, however, which is something the drug has not been found conclusively to do for men.
"What was really surprising and not anticipated was this gender difference," said Dr. Elizabeth G. Nabel, director of the National Heart, Lung, and Blood Institute, which helped finance the Women's Health Study.
The study of healthy women over the age of 45, conducted by researchers at Brigham and Women's Hospital in Boston, was the first large clinical trial to look specifically at the effects of aspirin on women. Past aspirin studies had been focused entirely or largely on men.
The results were presented today at the American College of Cardiology meeting in Orlando, and they will be published in the March 31 issue of The New England Journal of Medicine.
The number of heart attacks suffered by the women who were taking aspirin was about the same as in the placebo group.
But the number of strokes in the aspirin group was 17 percent lower. And the aspirin takers had an especially low risk of ischemic stroke, the most common kind, caused by a blood clot in an artery leading to the brain - 24 percent lower than that for the placebo group.
The risk of hemorrhagic stroke, the kind that is caused by bleeding, was slightly higher in the aspirin group, as expected, because aspirin reduces the blood's tendency to clot.
"The fact that there was a benefit on stroke is very important for women," said Dr. Julie E. Buring, the principal investigator, "because we had many more strokes in our study than we had heart attacks."
Over the 10 years that the study was conducted, the subjects had a total of 391 heart attacks and 487 strokes.
The greater number of strokes points up what may be an important difference between men and women. It may explain why heart disease is often considered less of a problem for women than for men - despite the fact that more women than men die of it each year, Dr. Nabel said.
"Perhaps in the past cardiologists have focused a lot on the heart and heart attacks and haven't focused sufficiently on strokes," Dr. Nabel said. "Perhaps this will lead cardiologists, neurologists, internists and family practitioners to think more broadly about how cardiovascular disease really affects the heart and the brain."
Given that both strokes and heart attacks are caused by blood clots in arteries, it is not immediately clear why aspirin would protect women only against strokes. The explanation may have something to do with the fact that the blood vessels leading to the brain are somewhat smaller than those leading to the heart, Dr. Buring said.
Dr. Buring said recommendations for aspirin use by women who have not had a heart attack or stroke should be reconsidered in light of the new findings. "We need to look at whether this additional complexity in women should be factored in in some way," she said.
Among women who took aspirin, the risk of all "cardiovascular events" together - including heart attacks, strokes and death from cardiovascular problems - was 9 percent lower than that for the placebo group. That difference was not significant, the researchers said.
"The major message from this is that low-risk women do not derive a protective benefit against heart disease from low-dose aspirin," said Dr. Sidney C. Smith, director of the center for cardiovascular medicine at the University of North Carolina at Chapel Hill, who helped write the American Heart Association's guidelines for preventing heart disease in women.
Only for the 4,000 women in the study who were age 65 or older did aspirin appear to be protective. The aspirin takers in this age group had a 26 percent lower risk of a major cardiovascular event than those who took placebos. Their risk of heart attack, in particular, was 34 percent lower.
Dr. Buring noted that a woman's risk of heart attack rises later in life than a man's. It goes up particularly after she passes menopause, presumably because that is when she loses the protective effect of natural estrogen.
"It could be that by age 65, women are just getting old enough that they are having heart attacks so that they would get a benefit from taking aspirin," she said. "It appears that for women over 65 there may be a net benefit from taking low-dose aspirin, but for women under 65 there might not be."
Studies in men have indicated that aspirin protects them against heart attacks. In 1989, for example, the Physicians' Health Study of healthy men between the ages of 40 and 84 found that those who took 325 milligrams of aspirin (the amount in a standard pill) every other day saw a 44 percent reduction in their risk of heart attack.
Subsequent studies using smaller doses of aspirin showed a similar benefit in men.
The amount of aspirin taken by subjects in the Women's Health Study - 100 milligrams every other day - is less than the amount one gets from taking a baby aspirin, which contains 81 milligrams, every day. But the researchers noted that the smaller amount still had the intended effect on blood clotting, as evidenced by blood analyses, by the fact that the women taking aspirin had a lower risk of stroke, and by the fact that they also had more instances of bleeding.
The women in the aspirin group had 40 percent more episodes of severe gastro-intestinal bleeding than those in the control group, and the aspirin takers also experienced more episodes of minor bleeding and bruising.
Because aspirin therapy carries a risk of bleeding, doctors recommend it only for men and women with an elevated risk of heart disease-gauged by factors like high blood pressure, a family history of heart disease, diabetes, smoking and obesity.
The United States Preventive Services Task Force, which issues medical practice guidelines, recommends that doctors consider aspirin therapy for men and women whose five-year risk of heart disease is at least 3 percent.
The American Heart Association distinguishes between men and women in assessing the level of risk. Men whose risk of heart disease in the next 10 years is at least 10 percent are considered candidates for aspirin therapy. But women should not be advised to take aspirin unless their 10-year risk is 20 percent, or if it is 10 percent and they have controlled high blood pressure.
The new results from the Women's Health Study validate setting a higher level of risk for women, Dr. Smith said. "The really big message here is that women need to know their risk," he said.
People who already have suffered a heart attack or stroke are typically advised by their doctors to take low-dose aspirin daily, because studies have clearly shown its benefit in preventing subsequent heart attacks. Aspirin is also recommended for people who are experiencing symptoms of a heart attack. "If you're having a heart attack, it means you have a clot already," Dr. Buring said. "If you take an aspirin, it will keep another clot from forming."
The Women's Health Study was also designed to measure the effect of taking vitamin E supplements. Subjects were randomly assigned to take 600 international units of vitamin E pill or a placebo every other day. The supplements appeared to have no effect in preventing heart disease or stroke or in causing any health problems.
"What was really surprising and not anticipated was this gender difference," said Dr. Elizabeth G. Nabel
Don't let the people at Harvard hear about this or they throw Nabel down the well with Summers.
Thanks, Nick. I think I'll ask my doctor about it first . . .
There are no differences between men and women.
Repeat the above 1000 times.
It still won't be true.
The calculator link at the bottom was obtained from the USPSTF link. It's intended for the health professionals on my list. For all others, please discuss with your health care providers before you start taking low dose aspirin.
Aspirin for the Primary Prevention of Cardiovascular Events, U.S. Preventive Services Task Force
American Heart Association updates heart attack, stroke prevention guidelines
I've taken a full-strength aspirin per day for a number of years. My doctor raised it to TWO aspirin a day when he took me off Bextra, because he said you need two to get the anti-inflammatory effect. Must be careful to take it with water and on a full stomach.
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