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Doc: Aspirin therapy’s usefulness depends on risks

December 21, 2018

Dear Dr. Roach: Like many men, I have been taking 81-mg aspirin for decades. I recently saw a report indicating that not only is it not helpful, but that it actually can increase the risk of internal bleeding and the likelihood of death from cancer. What is your advice on the wisdom of continuing to take the aspirin?

T.M.

Dear T.M.: Aspirin has been used for 50 years or more to prevent heart attacks. Several studies in the 1980s and 1990s confirmed that aspirin is effective at preventing the first heart attack in men at average or high risk for heart disease. One trial was so persuasive that it was stopped early, as it was deemed unethical to allow the men on placebo to continue without being offered aspirin. The Women’s Health Study in 2001 showed that aspirin reduces risk of stroke in women.

However, aspirin has a well-known risk: It can cause bleeding, especially of the stomach and GI tract, but inside the brain, as well. In comparing the risks and benefits, the studies showed that between 30 and 200 men need to be treated with aspirin for five years in order to prevent a heart attack, while one man in 100 or so will develop a bleed bad enough to require hospitalization or transfusion. In the Women’s Health Study, about 500 women needed to be treated for 10 years to prevent one stroke, while one woman in 25 developed bleeding. Of course, some bleeding (such as nosebleeds or blood in the urine) does not have the same effect on quality of life as a stroke.

Three trials recently have been published questioning the effectiveness of aspirin to prevent the first heart attack (I emphasize FIRST heart attack because everyone with a history of a heart attack should be on aspirin unless there is a reason for them not to be on it, such as a prior history of bleeding). One of these trials, the ASPREE study, showed that aspirin did not reduce risk of a heart attack in people over 70, but did increase risk of bleeding. Aspirin also increased risk of dying from cancer in this study. This was unexpected. A review of all the previous trials showed that aspirin doesn’t increase or decrease risk of stroke in the first 10 years people take it, but after 10 years, risk of all cancer (but especially colon cancer) decreased by almost 50 percent. The ASPREE trial had follow-up for only five years.

Still, researchers have puzzled over why aspirin showed benefit in the 1980s and 1990s, but the recent trials have shown smaller-than-expected benefit (the ASCEND trial showed one fewer heart attack per 100 men over nine years) or none (the ARRIVE trial showed no improvement compared with placebo). I think the answer comes from the fact that heart disease is much less prevalent now than it was 20-30 years ago. Despite a worsening in some risk factors in the population (obesity), there is less smoking, better control of blood pressure and far more use of statin drugs, which cumulatively act to reduce heart attack and stroke risk. Aspirin will thus have less benefit to a population, but the same risk of bleeding, meaning the risk/benefit ratio is less favorable.

However, doctors don’t treat populations; we treat individuals. Some individuals still will have enough heart disease risk to warrant aspirin therapy. Additionally, since long-term use of aspirin reduces colon cancer risk, people at high risk for colon cancer may develop benefit there. Because people older than 70 have higher risk for bleeding, the risks may outweigh the benefits for them.

Email questions to ToYourGoodHealth@med.cornell.edu.

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