In healthy elderly people who never had a heart attack, the widespread practice of taking a baby aspirin every day may do more harm than good, according to a U.S.- Australian study of more than 19,000 volunteers.

The trial has "provided convincing evidence that aspirin is ineffective in preserving good health in elderly people without a medical (reason) to be using it," chief author Dr. John J. McNeil of Monash University in Melbourne told Reuters Health in an email.

The results - which show that risks of major bleeding in low-dose aspirin users overwhelm any heart benefits - were reported online in the New England Journal of Medicine and presented Sunday at the European Respiratory Society International Congress in Paris.

The findings may upend a common practice.

For people trying to prevent a second heart attack or stroke, evidence in support of baby aspirin therapy remains strong. But the new study, known as ASPREE, looked at the long-standing question of whether a first heart attack, stroke, or case of heart failure could be prevented with small amounts of the blood thinner in aspirin.

Until now, the balance between risks and benefits in older individuals was unclear, said Dr. McNeil.

Most volunteers had to be at least 70 years old. Patients who were black or Hispanic and living in the U.S. - two groups that face a higher risk of heart disease or dementia - could be age 65 or older. At the start of the study, all were expected to survive for at least five years.

After about five years of treatment, the rate of heart disease was not significantly lower in the 9,525 volunteers taking 100 mg of aspirin daily than in the 9,589 who took placebo tablets.

But the odds of a major bleeding episode were 38 percent higher with aspirin. Problems like stroke and intestinal bleeding occurred in 8.6 percent of aspirin patients versus 6.2 percent of placebo patients.

"This should set the record straight," said Dr. Vincent Bufalino of the Advocate Heart Institute in Chicago, who was not involved in the study. "There's a lot of folks on both sides of this but this study should end the question. There is no benefit for seniors who do not have vascular disease."

"I've spent the last five, six years trying to get all my seniors to stop taking aspirin" based on the clear risks and unproven benefit, he told Reuters Health by phone. "If you look at the new findings, at best it's neutral and at worst it increases the bleeding risk."

And what about people with high blood pressure or high cholesterol who might be taking other medicines to mitigate a higher risk of heart attack or stroke? In the new study, most volunteers fell into that category and aspirin didn't seem to help them.

"Essentially, we could not identify any subgroup in whom aspirin was beneficial in preserving good health," Dr. McNeil said.

The ASPREE study was stopped early as it became clear that the "wonder drug" wasn't working wonders.

While there were 21.5 cases of death, dementia or disability per 1,000 patients each year in the aspirin group, the rate was 21.2 with placebo. The difference wasn't statistically significant, meaning it could have been due to chance.

But the rate of major bleeding with daily aspirin use was 3.8 percent, versus 2.8 percent with placebo.

When the McNeil team looked at death from any cause, aspirin still made no difference statistically, with a rate of 12.7 per 1,000 patients each year with aspirin and 11.1 with placebo.

Extra cases of cancer were the chief reason for the higher death rate, with 3.1 percent of aspirin users dying of cancer versus 2.3 percent in the control group.

The higher pace of cancer deaths became apparent three and a half years after the study began, particularly death from stomach and intestinal tumors.

The cancer finding surprised researchers because in other studies, aspirin protected against death from cancer.

Thus, McNeil team said, the cancer results "should be interpreted with caution."

The study was coordinated at 34 sites in the U.S. and 16 in Australia.