Our findings mean millions of healthy people over the age of 70, and their doctors, will now know daily aspirin is not the answer to prolonging good health.
If you are a healthy older person and take a low-dose aspirin every day, it may be more harmful than you think.
Experts said the findings showed many older people may be taking the medicine "unnecessarily" and that it is "really of very little benefit".
He cautioned that the results do not apply to those with existing conditions such as a previous heart attack, angina or stroke, where aspirin is recommended as a valuable preventive drug.
The results of the Aspirin in Reducing Events in the Elderly (ASPREE) trial have been published in three papers in the New England Journal of Medicine. It involved 19,114 older people, with 16,703 in Australia and 2,411 in the United States.
But the rate of major bleeding with daily aspirin use was 3.8 per cent, versus 2.8 per cent with placebo.
"Cancer was the major contributor to the higher mortality in the aspirin group, accounting for 1.6 excess deaths per 1000 person-years". But the researchers interpreted the data cautiously, because other studies have shown aspirin to have a protective effect against colorectal cancer.
Dr Nespolon said while there have been mixed opinions on whether giving healthy people aspirin is a good idea, this new study "clearly shows people over 70 shouldn't be taking aspirin as simply an aid to their health".
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In the study, a preventive regimen of daily aspirin did not lower the risk of having a heart attack or stroke, but it did significantly increase the risk of bleeding in the gastrointestinal tract or brain - bleeding severe enough to require hospitalization and/or blood transfusions. But a large, new, global study finds that, even at low doses, long-term use of aspirin may be harmful - without providing benefit - for older people who have not already had a heart attack or stroke.
The trial was supported by grants from the National Institute on Aging and the National Cancer Institute at the NIH; the National Health and Medical Research Council of Australia; Monash University; and the Victorian Cancer Agency.
The primary risk is bleeding.
The participants were followed for around 4.7 years and could also not have dementia or a physical disability and had to be free of medical conditions. Do you take aspirin regularly?
But the trial found no benefit for healthy people over the age of 70, and the pills increased the risk of potentially fatal internal bleeding.
As would be expected in older people, cancer was a common cause of death, and 50 per cent of those who died in the trial had some type of cancer. The patients who took aspirin didn't report differences in dementia or physical disability compared to the control group.
"The rate of major hemorrhage was 8.6 events per 1000 person-years and 6.2 events per 1000 person-years, respectively (hazard ratio, 1.38; 95% CI, 1.18 to 1.62; P 0.001)". In the new study, most volunteers fell into that category and aspirin didn't seem to help them. The rates of coronary heart disease, heart attacks and strokes were also similar.
Older adults should follow the advice from their own physicians about daily aspirin use, Hadley said.