Though heart disease and stroke are equal-opportunity diseases, they affect men and women differently. Women, for instance, typically develop heart disease a decade later than men. In the U.S. nearly as many women as men die from heart attacks, but women are more likely to die from strokes. These disparities are largely due to biology. Scientists now know that women have smaller coronary arteries, for instance, and that artery-narrowing plaque develops somewhat differently in women. Hormones help explain some of these cardiovascular differences.
Now a long-awaited study on low-dose aspirin as a preventive for cardiovascular disease reveals other important gender differences.
Research on low-dose aspirin has been done largely with men, primarily because heart disease used to be seen as a man's disease. It is known that aspirin reduces the risk of second heart attacks in men and, though there is less evidence, in women. As for healthy people, studies have found a protective effect against heart attacks, but have included few women. Do healthy women also benefit from low-dose aspirin? The Women's Health Study, published in March in the New England Journal of Medicine, provides some answers.
The 10-year study, the largest and best so far, included nearly 40,000 healthy women age 45 and older (the great majority health-conscious and under 65). Half took low-dose aspirin every other day; half took a placebo. Here are the key findings:
Overall, aspirin did not reduce the risk of a first heart attack or death from cardiovascular disease, as it does in men. This is the headline you may have seen in the newspaper. But age was a crucial factor. In women over 65, aspirin did reduce the risk of heart attacks by 34%.
Aspirin reduced the risk of ischemic stroke (the most common type) by 24%, on average, but most of the benefit was seen in women over 65. There was an increased risk of hemorrhagic (bleeding) stroke--not surprising, since aspirin reduces blood clotting--but this was not statistically significant. Most studies on men have not found protection against ischemic stroke.
Women taking aspirin were more likely to have gastro-intestinal bleeding, a well-known and potentially serious side effect. To put this in perspective, among the 20,000 women taking aspirin, 51 ischemic strokes were prevented over 10 years, but an extra 160 cases of gastrointestinal bleeding (36 requiring transfusions) occurred.
What this means for women
In light of these new findings, doctors should consider aspirin therapy for women over 65, especially those at high risk for heart attack or stroke. The risk factors include hypertension, high blood cholesterol, obesity, diabetes, inactivity, smoking, and a family history of cardiovascular disease. For women under 65, aspirin's benefit remains unproven, unless they've already had a heart attack.
Because of the risk of gastrointestinal bleeding, no one--man or woman--should start taking low-dose aspirin without first consulting a doctor. This is especially true of people with uncontrolled hypertension (since they are at increased risk for a hemorrhagic stroke, and aspirin increases the risk), those with bleeding disorders or a history of ulcers, and those regularly taking nonsteroidal anti-inflammatory drugs (such as ibuprofen or naproxen) for pain relief.
Note: This study used an unusual aspirin regimen, 100 milligrams (about one-third of a full-dose aspirin) every other day. Typically one-quarter aspirin (81 milligrams, or a "baby" aspirin) is taken daily, or half an aspirin (162 milligrams) every other day. But, according to the researchers, blood tests showed that this regimen was also effective. A given dose of aspirin produces higher blood levels in women than in men. The fact is, no one really knows what the optimal dose is--for men or women.