The Effects of Aspirin on Heart Health

In antiquity, people chewed willow bark for its analgesic properties. Willow is rich in salicylate, the precursor to acetylsalicylic acid, the compound delivered today by common aspirin. It not only relieves pain, it reduces inflammation and fever. And within the last generation, aspirin has become the only over-the-counter analgesic that some health professionals have recommended to lower the risk of heart disease and stroke.

But the October issue of Harvard Men’s Health Watch suggests it might be wise to reconsider the regular use of aspirin for what it calls “primary prevention” of cardiovascular disease—that is, taking it an aspirin once a day when you don’t have heart disease but hope to prevent it.

Millions of Americans take a daily aspirin not for headaches but to hedge their heart health bets. They leave themselves at risk, according to Health Watch, for bleeding in the upper gastrointestinal (GI) region -- i.e., stomach and esophagus -- and the brain.

When blood vessels are constricted or obstructed, blood flow is reduced. Blocked arteries can cause heart attacks and strokes, so some people take aspirin because it suppresses the ability of blood to clot by making platelets less "sticky." The same trait raises the risk for bleeding in the gut and brain. “The critical question,” Health Watch says, “is whether your risk of cardiovascular disease outweighs the risk of bleeding. Right now, the answer is not simple.”

See our blog from last year about the danger of taking aspirin along with other pain relievers.

The risks are not the same for someone taking low-dose aspirin for “secondary prevention,” or those who have had a heart attack, certain kinds of stork or other cardiovascular disease. They have a high risk of additional problems, so the question of balance is clear: Aspirin is their friend (unless they are allergic to it or have a major bleeding issue).

Out of 10,000 people with a heart problem history, aspirin can prevent 250 cardiovascular events (heart attacks, strokes and sudden death). That same group will experience 40 cases of serious bleeding. For every six people helped, one will be harmed. “That's little consolation if you're sent to the hospital with internal bleeding,” Health Watch says, “but as a public health policy this risk equation is acceptable.”

Is it acceptable for you? Probably not if you’re taking it prophylactically, or to prevent a heart “event.”

On average, for every 10,000 people taking low-dose aspirin, seven people will be helped (mostly by preventing heart attacks) and four will be harmed. Individual risk, of course, varies depending on your health profile and lifestyle choices. The benefit of aspirin rises with age, being overweight, smoking and having high cholesterol. The risk of bleeding also rises with age, but so does the risk of heart attacks and strokes, and, therefore, the potential benefit of taking aspirin.

A study in the Journal of the American Medical Association (JAMA) added fuel to the prophylactic aspirin fire. Analyzing health records in the Italian National Health Service, researchers concluded that the study “demonstrated that the incidence of major bleeding events is much higher than that recorded in randomized, prospective clinical trials. …We found a 5-time higher incidence of major bleeding leading to hospitalization among both aspirin users and those without aspirin use.”

That study involved a wide range of patients; Health Watch says some probably would have had a higher risk of bleeding than the previous trial patients, which could explain the higher incidence of bleeding. That study also didn’t define the benefits of aspirin, which could have been significant.

For now, the science remains uncertain and experts disagree about who should take aspirin to prevent a first heart attack or stroke. European cardiology guidelines don’t recommend aspirin for primary prevention. In the U.S., the FDA has not approved aspirin labels touting cardiovascular disease prevention.

That could change if better primary prevention trial results indicate they should. But unless and until that happens, what should you do? First, know your medical history and health profile. In other words, know as much as you can about your risk for developing heart problems. You can’t weigh potential harm against potential benefit without this information. And if you already take low-dose aspirin to head off cardiovascular disease, discuss the wisdom of this practice with your doctor.