A large clinical trial of thousands of healthy older people with no history of heart problems or stroke finds that taking a low dose of aspirin per day did not help them live a longer life free of disability or dementia.

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Taking daily aspirin does not contribute to a longer, disability-free life.

The researchers, however, point out that further analysis needs to be done to determine the risk of dying from specific causes — including heart disease and cancer.

Called Aspirin in Reducing Events in the Elderly (ASPREE), the double-blind, randomized, and placebo-controlled international trial is still going, and the new findings are the early results.

Three papers now published in the New England Journal of Medicine present and discuss these early findings: the first focuses on cardiovascular events and bleeding, the second addresses disability-free survival, and the third concerns death from all causes.

Need to assess benefits, risks in older people

The main reason for the research was that the benefits and risks of older people taking a low dose of daily aspirin had not been weighed up.

Previous studies had demonstrated that "low-dose aspirin therapy" can reduce the risk of "vascular events" such as heart attack and stroke, but these had largely addressed middle-aged people.

Also, they had mainly focused on cardiovascular outcomes, whereas the "most desirable" impact of preventive medicine on older people should be to help them live longer "free of functional disability."

"Clinical guidelines," says Richard J. Hodes, who is director of the National Institute on Aging (NIA), "note the benefits of aspirin for preventing heart attacks and strokes in persons with vascular conditions such as coronary artery disease."

"The concern has been uncertainty about whether aspirin is beneficial for otherwise healthy older people without those conditions," he adds.

The NIA is one of the National Institutes of Health (NIH) and one of the collaborators in the trial.

Study design

ASPREE started in 2010 and recruited 16,703 older people aged 70 and older in Australia and 2,411 in the United States. The average follow-up for the recent findings was 4.7 years. The final completion date is January 2019.

The admission age was 65 and older only for African-American and Hispanic recruits in the U.S. because these groups have a higher risk of developing cardiovascular disease and dementia.

Anybody with a physical disability, dementia, or one or more conditions that required them to take aspirin was excluded from the study.

Of the 19,114 people recruited to the trial, 9,525 were randomly assigned to take 100 milligrams of aspirin per day and 9,589 to take placebo.

Key preliminary findings

Overall, the findings have so far revealed that the daily low-dose aspirin had no effect on dementia- and disability-free survival compared with placebo.

Of the individuals who took aspirin, 90.3 percent were alive and free of dementia and "persistent physical disability" at the end of the follow-up period. This compared with 90.5 percent who took placebo. Incidence of dementia was the same in both groups, and rates of disability were largely similar.

Rates of nonfatal heart attacks, coronary heart disease, and nonfatal and fatal ischemic stroke were also largely similar in the aspirin and placebo groups.

It is well-known that taking aspirin regularly can raise the risk of significant bleeding. The recent results reveal a significantly higher risk of this happening — in the stomach and intestines as well as the brain — in the aspirin group.

Half of the deaths during the follow-up occurred in people with cancer. This is not unexpected in a study of older adults.

What was surprising was that there appears to have been a higher risk of cancer-related death in the aspirin group, given that studies have suggested that aspirin can reduce it.

The team is now carrying out an analysis of all the cancer-associated data of the trial and urging others to treat this particular finding "with caution" until that analysis is complete.

A further 19 percent of deaths were due to stroke and heart disease and 5 percent to major bleeding.

Further work to be done

"Continuing follow-up of the ASPREE participants is crucial," states Evan Hadley, the director of the Division of Geriatrics and Clinical Gerontology at the NIA, "particularly since longer-term effects on risks for outcomes such as cancer and dementia may differ from those during the study to date."

The team has already begun to put in place plans to monitor the individuals in the longer-term, and to continue the data analysis.

In the meantime, says Hadley, older people should seek advice from their physicians about the use of aspirin as a preventive measure.

He explains that the point of the trial was not to study people who are taking aspirin because they are known to be at higher risk of cardiovascular events and so cannot comment on this group.

Also, the findings do not apply to those under the age of 65. In addition, the results are not robust enough to indicate whether healthy older people who are already taking aspirin as a preventive measure should carry on or stop. Only a further study can answer that question.

"These initial findings will help to clarify the role of aspirin in disease prevention for older adults, but much more needs to be learned."

Evan Hadley