LONDON -- One or two baby aspirins a day -- not the standard dose of regular strength adult aspirin -- are enough to lower the risk of heart attack or stroke for those at high risk, major new research shows.
The study also found that aspirin can help a wider range of people with potential heart trouble.
Aspirin is the cornerstone of blood thinning treatment for people who have had a heart attack or stroke but is not normally used for those who suffer ailments that put them at risk for those conditions, such as diabetes, chest pain, irregular heart beat and diseased leg arteries.
The latest research found that aspirin reduced the risk of heart attack or stroke, or death from those events, by 25 percent -- even when the patients had not had a heart attack or stroke previously.
The findings come from an analysis that combines evidence accumulated over the years on the effectiveness of aspirin and its alternatives in staving off heart trouble. Coordinated by scientists at Oxford University in England, it encompassed 287 studies involving more than 200,000 people.
The most crucial advance offered by the study is in defining the appropriate dose of aspirin for long-term therapy, said Dr. Eric Topol, cardiology chief at the Cleveland Clinic, who was not involved in the analysis.
"That's a big thing. Before this analysis we weren't sure what the dose was at all," Topol said. "Three hundred twenty-five milligrams was readily available, so it was used out of convenience, but now I think we've zeroed in on the range of 80 to 160."
Most doctors and heart specialists use a dose of 325 milligrams of aspirin per day when applying it as a blood thinner. That's the dose in a regular strength adult aspirin tablet.
The latest analysis shows that 75 to 150 milligrams works just as well, with less chance of internal bleeding.
In the United States, baby aspirin, also available as low-dose adult aspirin, contains 81 milligrams.
In Europe aspirin comes in doses of 75 milligrams and 300 milligrams.
"There are two problems," Topol concluded. "Doctors are giving too much or they are not giving any at all. We have a lot of work to do now to get all the patients treated and at the right dose."
"That dose should be considered to be one or two baby aspirin and not the standard 325 milligrams," he said.
A similar analysis performed in 1994 by the same group solidified the role of long-term daily aspirin treatment for preventing second heart attacks or strokes in patients who have already had one.
The latest review, published in the British Medical Journal, is a much-anticipated update.
"We've got clear evidence now from this review that people who haven't yet had a heart attack or stroke do benefit, but they are being treated less than half the time with aspirin," said one of the investigators, Dr. Colin Baigent, an epidemiologist at Oxford University.
"If we were to tackle that group, that would save about 40,000 extra lives a year worldwide," he said.
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