And there is some evidence that daily low-dose aspirin may help people younger than 70 who have at least a 10 percent risk of having a heart attack avoid a heart attack or stroke, according to the latest recommendations from the U.S. Preventive Services Task Force.
But for older, healthy people, "the risks outweigh the benefits for taking low-dose aspirin," Murray says.
The primary risk is bleeding. The study confirmed that a daily baby aspirin increases the risk for serious, potentially life-threatening bleeding.
Surprisingly, those who took daily aspirin also appeared to be more likely to die overall, apparently from an increased risk of succumbing to cancer. That was especially unexpected given previous evidence that aspirin might reduce the risk for colorectal cancer.
The researchers stressed, however, that the cancer finding might have been a fluke. There's also a possibility that any colorectal cancer benefit wasn't seen because the subjects had only been followed for about five years.
Regardless, the findings raise serious questions as to whether otherwise healthy older people should routinely take low-dose aspirin.
"A lot of people read, 'Well, aspirin is good for people who have heart problems. Maybe I should take it, even if they haven't really had a heart attack,' " Murray says. But "for a long time there's been a need to establish appropriate criteria for when healthy people — elderly people — need aspirin."
That's why the researchers launched their study, called ASPREE, in 2010. It involved 19,114 older people, with 16,703 in Australia and 2,411 in the United States. The U.S. portion included white volunteers ages 70 and older, and African-Americans and Hispanics subjects ages 65 and older.
Participants took either 100 milligrams of aspirin every day or a placebo. People in the study were followed for an average of 4.7 years.
"We were hoping that an inexpensive, very accessible medication might be something that we could recommend to elderly to maintain their independence but also decrease their risk of cardiovascular disease," Murray says.
But based on the findings, Dr. Evan Hadley of the National Institute on Aging, which helped fund the study, says any elderly people taking aspirin or thinking about it should think twice.