By Denise Grady
Should older people in good health start taking aspirin to prevent heart attacks, strokes, dementia and cancer?
No, according to a study of more than 19,000 people, including whites 70 and older, and blacks and Hispanics 65 and older. They took low-dose aspirin — 100 milligrams — or a placebo every day for a median of 4.7 years. Aspirin did not help them — and may have done harm.
Taking it did not lower their risks of cardiovascular disease, dementia or disability. And it increased the risk of significant bleeding in the digestive tract, brain or other sites that required transfusions or admission to the hospital.
The results were published on Sunday in three articles in The New England Journal of Medicine.
One disturbing result puzzled the researchers because it had not occurred in previous studies: a slightly greater death rate among those who took aspirin, mostly because of an increase in cancer deaths — not new cancer cases, but death from the disease. That finding needs more study before any conclusions can be drawn, the authors cautioned. Scientists do not know what to make of it, particularly because earlier studies had suggested that aspirin could lower the risk of colorectal cancer.
The researchers had expected that aspirin would help prevent heart attacks and strokes in the study participants, so the results came as a surprise — “the ugly facts which slay a beautiful theory,” the leader of the study, Dr. John McNeil, of the department of epidemiology and preventive medicine at Monash University in Melbourne, Australia, said in a telephone interview.
The news may also come as a shock to millions of people who have been dutifully swallowing their daily pills like a magic potion to ward off all manner of ills. Although there is good evidence that aspirin can help people who have already had heart attacks or strokes, or who have a high risk that they will occur, the drug’s value is actually not so clear for people with less risk, especially older ones.
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The new report is the latest in a recent spate of clinical trials that have been trying to determine who really should take aspirin. One study published in August found no benefit in low-risk patients. Another found that aspirin could prevent cardiovascular events in people with diabetes, but that the benefits were outweighed by the risk of major bleeding.
A third study found that dose matters, and that heavier people might require more aspirin to prevent heart attacks, strokes and cancer.
The newest findings apply only to people just like those in the study: in the same age ranges, and with no history of dementia, physical disability, heart attacks or strokes. (Blacks and Hispanics were included in the study at a younger age than whites because they have higher risks than do whites for dementia and cardiovascular disease.) In addition, most did not take aspirin regularly before entering the study.
The message for the public is that healthy older people should not begin taking aspirin.
“If you don’t need it, don’t start it,” Dr. McNeil said.
But those who have already been using it regularly should not quit based on these findings, he said, recommending that they talk to their doctors first.
Dr. McNeil also emphasized that the new findings do not apply to people who have already had heart attacks or strokes, which usually involve blood clots. Those patients need aspirin, because it inhibits clotting.
The study, named Aspree, is important because it addresses the unanswered question of whether healthy older people should take aspirin, said Dr. Dr. Evan Hadley, director of the division of geriatrics and gerontology at the National Institute on Aging, which helped pay for the research. The National Cancer Institute, Monash University and the Australian government also paid. Bayer provided aspirin and placebos, but had no other role.
“For healthy older people, there’s still a good reason to talk to their doctors about what these findings mean for them individually,” Dr. Hadley said. “This is the average for a large group. A doctor can help sort out how it applies individually. It’s especially important for people already taking aspirin who are over 70. The study didn’t include many people who had been taking it, and doesn’t address the question of continuing versus stopping.”
The most widely used guidelines for using aspirin to prevent disease came out in 2016 from experts at the United States Preventive Services Task Force. They recommend the drug to prevent cardiovascular disease and colorectal cancer in many people aged 50 to 59 who have more than a 10 percent risk of having a heart attack or stroke during the next 10 years. (That risk, based on age, blood pressure, cholesterol and others factors, can be estimated with an online calculator from the American Heart Association and the American College of Cardiology.)
For people 60 to 69 with the same risk level, the guidelines say it should be an individual decision whether to take aspirin.
But for people 70 and over, the guidelines say there’s not enough evidence to make any recommendation.
Aspree was designed to fill the information gap for older people.
Rather than looking only at individual ailments, the study also tried to evaluate aspirin’s effect on “disability-free survival,” meaning whether it could help older people prolong the time in which they remain healthy and independent.
“Preventive medicine is focusing on older people, how to keep them out of nursing homes, alive and healthy,” Dr. McNeil said. ”Why would an elderly person be taking a drug if it doesn’t keep them alive and healthy any longer? A lot of the previous studies have looked at aspirin and heart disease. But a lot of drugs do good things and bad things. Just looking at one doesn’t seem to be enough.”
The study enrolled 16,703 people from Australia, and 2,411 from the United States, starting in 2010. They were assigned at random to take low-dose aspirin (100 milligrams a day) or a placebo. That is slightly more than the widely sold dose that most people take, 81 milligrams.
With a median follow-up of 4.7 years, the two groups had no significant difference in their rates of dementia, physical disability or cardiovascular problems.
But those on aspirin were more likely to have serious bleeding — it occurred in 3.8 percent, as opposed to 2.7 percent in the placebo group.
The death rates also differed: 5.9 percent in the aspirin group, and 5.2 percent in those taking placebos. Much of the difference was the results of a higher rate of cancer deaths.
Dr. McNeil said his team could not explain the apparent increase in cancer deaths. They wondered if excess bleeding might have contributed to deaths in cancer patients, but did not find evidence of it. They will continue to follow the participants, and to study tissue samples from cancer patients who died.
Although it may seem counterintuitive, he said the cancer finding does not rule out the possibility that aspirin can help prevent colorectal malignancies. The protective effect may not show up until people have been taking aspirin for some time, longer than the average follow-up in the study.
*A version of this article appears in print on Sept. 17, 2018, on Page A14 of the New York edition with the headline: Healthy Older People Should Avoid Aspirin Regimen, New Research Shows.