Harvard Men's Health Watch

Aspirin: Heart healthy but know the risks

Daily aspirin offers a small benefit, but can cause bleeding, too.

The cornerstones of heart health are a healthy diet and exercise, but for some men daily aspirin also has a role. For anyone who has already experienced a heart attack, stroke, or other problem related to clogged arteries, aspirin is strongly recommended because it prevents more problems than it causes—the biggest concern being unwanted bleeding. But for otherwise healthy men who want to prevent cardiovascular disease, preventive aspirin remains controversial.

In May 2014, the FDA declined a request by Bayer for permission to market aspirin to prevent heart attack and stroke in people without diagnosed cardiovascular disease. That echoed the standing recommendation by the American Heart Association and other medical organizations that the decision to take preventive aspirin should be made case by case.

The reason: the most recent large clinical trials of people without diagnosed cardiovascular disease have found no overall benefit to taking a little
bit of aspirin every day to ward off heart attack and stroke—including in groups
at higher risk, like people with diabetes. But doctors are unwilling to rule out the option in all cases.

"It needs to be individualized," says Dr. Christian Ruff, a cardiologist at Harvard-affiliated Brigham and Women's Hospital. "You have to have a discussion with your doctor to see if you are at high enough risk to warrant aspirin."

A minority of people who take daily heart-protective aspirin ultimately benefit.

Aspirin: Benefits and risks

Here is what a study found after pooling the results of clinical trials on protective
aspirin in people without known cardiovascular disease:

  • 200 people had to take aspirin daily for 10 years to prevent one nonfatal heart attack.
  • Aspirin did not prevent fatal heart attacks, strokes, or death related to problems in the arteries or heart.
  • Daily aspirin use caused two cases of dangerous bleeding in the stomach, intestines, or brain.

Aspirin and clotting

When you nick a blood vessel shaving or sustain a serious injury, specialized cells in the blood called platelets stick together to stanch bleeding. That's good—but clotting is also involved in heart attacks and strokes.

Fatty deposits, or plaques, form in all men's arteries to a greater or lesser extent. If a plaque ruptures, the body interprets it as an injury and forms a clot. The clot can block an artery that nourishes the heart or brain.

Taking a small amount of aspirin every day can prevent harmful clotting. The downside is that aspirin may interfere with natural clotting when you don't want it to, leading to internal bleeding.

Benefits and risks

What's the benefit of taking aspirin if you don't have cardiovascular disease but want to do everything you can to avoid it? The most recent overall assessment is a 2012 study in Archives of Internal Medicine that pooled results from nine clinical trials involving a total of more than 100,000 people. It provides estimates of both the benefit and the risk of daily aspirin for otherwise healthy people.

Benefits. Daily aspirin slightly reduces the chance of nonfatal heart attacks. For every 200 people who take daily aspirin for 10 years, one such heart attack may be prevented. At the same time, it does not appear to protect against either stroke or death from cardiovascular disease.

Risks. Aspirin can cause bleeding in the stomach or intestines. Less commonly, the bleeding can happen in the brain. The study in Archives grouped both types of bleeding together. For every 200 people who took aspirin for 10 years, two instances of dangerous bleeding occurred.

Bottom line. Based on the best research available right now, most people who have not been diagnosed with cardiovascular disease would not benefit from taking daily aspirin long term. This is because they would be more likely to experience unwanted bleeding than be protected from nonfatal heart attacks. In otherwise healthy people, aspirin doesn't appear to prevent stroke or death from cardiovascular disease in general.

Preventive aspirin: What kind?

  • The typical daily dose is 81 milligrams (mg), but in some cases could be
    as much as 325 mg—the amount in one regular-strength pill.

  • "Stomach friendly" enteric-coated or buffered aspirin formulations
    do not eliminate the risk of bleeding.

  • Some studies have found that enteric-coated aspirin may
    have less anti-clotting effect than plain aspirin.

  • Taking aspirin with food may help reduce stomach problems.

Images: Thinkstock

Making your decision

The point at which the chance of being helped by daily aspirin outweighs the bleeding risk varies from person to person. This is why experts recommend an individualized assessment.

"You have to be more thoughtful when considering aspirin for prevention in people without known cardiovascular disease," Dr. Ruff says. "You need to assess the risk of having a heart attack or stroke and also the risk of bleeding."

Individual bleeding risk is tricky, Dr. Ruff says, because it varies so much from person to person. "We don't have the ability to predict it accurately. You have to weigh a lot of things that are not easy to plug into a formula," he says.

Here are the factors your doctor will need to consider:

  • Older age. The average risk of bleeding from aspirin use rises with age.

  • A past occurrence of bleeding in the stomach or intestines.

  • A previous ulcer. The chance of bleeding is two to three times higher in anyone who has had ulcers.

  • Use of medications that increase the chance of bleeding. These include nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids, and anticoagulants (blood thinners) like warfarin (Coumadin).

Don't play doctor

Some men have already started
taking a daily aspirin without checking in with their doctors, but it's not a safe move. "Although you don't need a prescription for aspirin, you should treat the decision to use it as if it were a prescription drug," Dr. Ruff says. "Make sure you talk to your doctor because that may uncover reasons why it could be dangerous for you to be on daily aspirin. Aspirin causes more bleeding in practice than almost any other medication we use because so many people are on it."