Peter Rothwell, professor of neurology at the Centre for the Prevention of Stroke and Dementia at the University of Oxford, said taking the tablets if healthy, over the age of 70 and have not had a previous heart attack or stroke, is "really of very little benefit".
Even worse, a third study on the topic found that those who used aspirin each day had a "higher all-cause mortality" among seemingly healthy older people than those who did not take aspirin.
The findings apply only to older adults who haven't developed a blood-vessel-related problem, however.
The clinical trial did not include people who take aspirin for medical reasons as advised by their doctor, including those who have already suffered a heart attack or stroke. However, studies in younger people showed that the risks outweighed the benefits and the new research confirms that the same is true for the elderly. "Unless the cardiovascular risk is very high ( 20% over ten years), prophylactic aspirin results in more harm than good".
The study involved 19,114 generally healthy volunteers (no history of cardiovascular disease, dementia or physical disability) living in Australia and the United States. Patients who were black or Hispanic and living in the U.S. were included in the study as they face a higher risk of heart disease or dementia generally. The age limit was lowered for those groups because blacks and Hispanics tend to be younger than whites when they have their first heart attack or stroke. But when researchers looked at more than 19,000 people in Australia and the United States over almost five years, they found it wasn't so.
At the end of the trial, 90.3 percent of the aspirin-treated patients were still alive, compared to 90.5 percent of those who received placebos.
They found that the rates for major cardiovascular events, which including coronary heart disease, nonfatal heart attacks, and fatal and nonfatal ischemic stroke, were similar in both groups.
The doctors unexpectedly found that those who took aspirin were slightly more likely to have died over the course of the trial (5.9%) than those who took the placebo (5.2%).
But the rate of bleeding was significantly different. Hemorrhagic stroke, bleeding in the brain, gastrointestinal bleeding and bleeding in other sites that required transfusion or hospitalization occurred in 361, or 3.8 percent, of participant in the aspirin-treated group and 265, or 2.7 percent, of those in the placebo group.
According to these three new studies, however, taking a low-dose aspirin daily is, at best, a waste of money for healthy older adults.
"Aspirin remains a relatively safe medication, but more research was needed to investigate the longer-term benefits and risks of its daily use", he said, adding that researchers were following the health of participants to determine if benefits, including cancer prevention, emerge from taking the drug over a period of time. This finding was surprising because nearly half of those extra deaths were due to cancer, including colorectal and other gastrointestinal cancers.