Aspirin and Heart Disease
From the publishers of the New England Journal of Medicine
A reader recently called us with some provocative questions: If aspirin can reduce the chances that someone will have a heart attack, why doesn't everybody take aspirin? And why should you talk with a doctor first?
For eight years now, we've been hearing about a connection between taking aspirin and reducing the risk of having a heart attack. The link appears to be so well established that pharmaceutical companies now make low-dose aspirin tablets especially for adults. In healthy people, though, the only thing that researchers have proved so far is that low-dose aspirin prevents first heart attacks in men. Whether aspirin can prevent strokes, or deaths from all cardiovascular disease—not just heart attacks and strokes but other vascular diseases—isn't yet known. Nor is the balance of benefits and risks in healthy women. We asked associate editor Charles Hennekens, whose 1988 paper clearly established aspirin's ability to prevent heart attacks in men, to discuss aspirin therapy.--The Editors
The Physician's Perspective
Charles H. Hennekens, MD
I wish there were simple answers to the reader's questions, but there aren't. Before we tackle them, we need to look at what we do know, and what we don't know, about aspirin and cardiovascular disease. Over the past 25 years, deaths from heart disease have dramatically declined. Much of this can be attributed to prevention. People today smoke less, treat their high blood pressure, and pay more attention to eating a diet low in saturated fats—all things known to reduce the incidence of cardiovascular disease. We have also improved our ability to treat heart attacks, and to treat people who have survived heart attacks and other vascular problems. Despite these significant advances, cardiovascular disease continues to be the leading cause of death in the United States. One important cause of cardiovascular disease is small clots that form in the bloodstream. These clots can block a cholesterol-narrowed artery that supplies heart muscle with the oxygen-rich blood it needs, thus killing cells and damaging the heart. Or they can cause strokes by blocking blood vessels that nourish the brain. Low doses of aspirin can prevent clots from forming by acting on platelets. These small, colorless blood cells accumulate at cuts and scrapes, forming a sticky plug that eventually stops the bleeding. But they can also clump together while circulating through the bloodstream. Aspirin prevents platelets from making a compound called thromboxane A2, without which they can't stick together and easily form clots. Aspirin's antiplatelet activity has been clearly proved in the laboratory. But in people, we know more about what it can do for those having a heart attack or those already diagnosed with cardiovascular disease than about what it can do for healthy people. Here is what we can say for certain:
 | Aspirin clearly reduces by 15 to 30 percent the chances that men or women who have already had any "vascular event" (e.g., a heart attack, stroke, angina, or other clot-caused circulatory problem) will suffer or die from a subsequent one. A recent study broadened the list of people who benefit from aspirin therapy to include people who recently had bypass surgery or angioplasty, those with chronic angina, and those with atrial fibrillation, a condition in which the upper chamber of the heart beats with a fast, irregular rhythm. |
| In both men and women, taking aspirin within 24 hours of a heart attack can reduce deaths by 25 percent and also reduce later heart attacks or strokes by almost half. |
| In terms of prevention, low-dose aspirin reduces the risk of having a first heart attack by about one third in men between the ages of 40 and 84. |
| Not all the news is positive. Regularly taking aspirin, even at low doses, increases the risks of gastrointestinal upset and bleeding in the stomach. It may even increase hemorrhagic strokes (bleeding into the brain). |
Recommendations for taking aspirin fall into two distinct categories: those involving treatment and those involving prevention. When it comes to treating people with cardiovascular disease or those who are in the midst of a heart attack, we need to be using aspirin more often. Between 20 and 50 percent of people in these two categories aren't receiving this effective therapy.
But in primary prevention, the evidence just isn't there yet to make blanket recommendations about aspirin. Clinical trials such as the Women's Health Study, in which half of the 40,000 initially healthy female health professionals are taking 100 mg of aspirin every other day, will give us some solid answers. Let me summarize by answering the questions that initiated this article: Why doesn't everyone take aspirin?Because only some people who take aspirin will reap a benefit from it, while everyone who takes it faces the possibility of suffering side effects. If you already have cardiovascular disease or have had a heart attack, you are almost certainly a candidate for low-dose aspirin therapy. But if you do not suffer from these circulatory problems, you will be a candidate only if the benefits outweigh the risks. For a healthy, 45-year-old woman, for instance, taking aspirin every day may increase the chances she'll have a bleeding side effect more than it lowers her heart-attack risk. For people diagnosed with cardiovascular disease or otherwise healthy people, 50 to 100 milligrams per day is sufficient. (That is approximately half a regular aspirin tablet, or a baby aspirin tablet, or one of the new, specially formulated tablets.) During a heart attack, however, 160 to 325 milligrams—a regular aspirin tablet—will be needed. Why is it necessary to consult with a doctor first?
Tallying the benefits and risks is something you should do with your health care provider. He or she can determine your risk of cardiovascular disease and, equally important, the likelihood that you might suffer side effects from aspirin therapy. Whether you do or don't have cardiovascular disease, aspirin should be used as an adjunct, not an alternative, to managing other risk factors. In other words, aspirin therapy alone won't counteract the damage done by continuing to smoke, eating a diet high in saturated fat, or living a sedentary lifestyle. We have proof beyond a reasonable doubt that avoiding these harmful behaviors has a much larger impact on preventing cardiovascular disease than does aspirin.
