Taking aspirin regularly may seem like a no-brainer. Decades of research, involving tens of thousands of subjects, suggests that daily or every-other-day use of aspirin protects against heart attacks, strokes and some cancers. The drug has a record of effectiveness against inflammation that’s more than a century old. It’s cheap, widely available, and requires no prescription.
But there's a tradeoff, and experts strongly recommend that we weigh the benefits and risks with a doctor before starting to take a daily aspirin. “It’s important to remember that even a daily low-dose 'baby' aspirin substantially increases the risk of serious gastrointestinal bleeding,” says Eric Jacobs, the American Cancer Society’s strategic director of pharmacoepidemiology. Such bleeding could land you in the hospital and in some cases can be fatal. Aspirin also raises one's risk of having a hemorrhagic stroke, in which a blood vessel in the brain becomes weak and bursts open, causing blood to leak into the brain. The bleeding risk from aspirin increases with age and is more likely to affect men than women. The larger the dose you take long-term, the greater the risk. If you take another nonsteroidal anti-inflammatory drug, like ibuprofen, along with aspirin, your bleeding risk will also rise. Buffered aspirins, while easier on your stomach, have not been proven to lessen the risk of gastrointestinal bleeding.
Who Should Take Aspirin
For some, the benefits of taking aspirin more than outweigh the risks. Studies have consistently shown that for patients at high risk of having a heart attack or stroke, either because they have cardiovascular disease or a condition that predisposes them to it, like diabetes, a long-term aspirin regimen can reduce the risk by one-quarter. Current guidelines recommend that people in these groups take aspirin as a regular preventive treatment — and, in general, a daily baby aspirin (81 milligrams) appears to be as effective as a daily regular-strength 325-milligram tablet.
“For people who’ve already had a heart attack or a stroke, unless there’s an absolute contraindication, everyone should be on it,” says epidemiologist Charles Hennekens of Florida Atlantic University’s Charles E. Schmidt College of Medicine. Those contraindications include an allergy to aspirin; regular alcohol consumption, which can increase bleeding risk; and a history of digestive tract bleeding, stomach or intestinal ulcers, or blood-clotting disorders. You also should not take aspirin if you are already taking a prescription anticoagulant (blood thinner).
Who Should Think Twice
The cost-benefit analysis is less clear for healthy people, without a family history of cardiovascular disease, who simply want to prevent a first heart attack or stroke, says Hennekens, who was the principal scientist for the Physicians’ Health Study, the first large-scale clinical trial to show that aspirin reduces the risk of a first heart attack. That study randomly assigned 22,000 healthy male doctors to take either a standard 325-milligram Bufferin aspirin tablet or a placebo every other day. Hennekens' team halted the study several years early because the benefits of aspirin were so clear. In 1989, they reported that the men who took aspirin were 44 percent less likely to have suffered a first heart attack than the men who took the placebo. “There’s no question that aspirin prevents a first heart attack,” Hennekens says, but he still believes that the risks are greater than the potential benefits for healthy people whose chance of a heart attack is relatively low.
Hennekens' advice is consistent with the recommendations of the U.S. Preventive Services Task Force, an independent group of experts supported by the federal Agency for Healthcare Research and Quality. That group advises that men age 45-79 take aspirin to reduce the risk of heart attack, and that women age 55-79 take it to reduce the risk of stroke, but only when the potential benefit outweighs the potential harm due to gastrointestinal bleeding. The group does not recommend regular use of aspirin for men under 45 or women under 55 and states that "current evidence is insufficient to assess the balance of benefits and harms of aspirin for cardiovascular disease prevention in men and women 80 years or older."
What We're Still Learning
Researchers are making new discoveries about the potential preventive benefits of aspirin that could lead to future changes in those recommendations. Recent studies conducted by researchers at the University of Oxford have found that daily aspirin use can reduce the risk of esophageal and colorectal cancer, and the recurrence of colon polyps that can become cancerous. While these findings are “exciting and promising," says Jacobs of the American Cancer Society, "it’s going to take some time for the medical community to review these data" and make recommendations.
Recent aspirin trials show a “substantial benefit” in cancer risk reduction for patients with Lynch syndrome, a rare inherited condition that raises the risk of a variety of cancers. People with Lynch syndrome have a lifetime risk of colorectal cancer of 52 percent to 82 percent. Questions remain about how much aspirin people with Lynch syndrome should take, Jacobs says. A recent clinical trial used a dosage of about 600 milligrams a day, the equivalent of two tablets, "but the thinking is that lower doses may well be equally effective,” Jacobs says, “because that’s true in heart disease and preventing the recurrence of colon polyps.”