May 28, 2009 -- Daily aspirin therapy is often recommended for otherwise healthy people who are at risk for heart attack or stroke, but a new analysis suggests that aspirin's risks may outweigh it benefits in this population.
It is clear that aspirin therapy is indicated in patients who have had a heart attack or stroke, as well as patients with established heart disease.
There has been much debate, however, about whether aspirin should be routinely recommended for the primary prevention of cardiovascular events in people who do not have heart disease or a history of cardiovascular events, but who have risk factors for such events.
On the benefit side, aspirin therapy has been proven to lower the risk for both primary and secondary heart attacks and non-bleeding-related strokes. On the risk side, its use is also associated with rare but potentially life-threatening gastrointestinal bleeding and strokes caused by bleeding.
In people without established heart disease, aspirin is usually recommended for those most at risk for having a heart attack or stroke.
But the new analysis reveals that these patients also have high risk for bleeding events.
"We found that the very people who are at increased risk for coronary heart disease are also at increased risk for bleeds," University of Oxford epidemiologist Colin Baigent, FFPH, tells WebMD.
Weighing Risks and Benefits
Baigent and a team of researchers from the U.K. conducted the analysis, which appears in the May 30 issue of The Lancet.
It included six high-quality primary-prevention studies with a combined enrollment of 95,000 low-to-average-risk people and 16 secondary-prevention studies with a combined enrollment of 17,000 high-risk patients.
The analysis revealed that:
- In both the low-to-average-risk and high-risk participants, aspirin therapy reduced the risk of nonfatal heart attacks by about a fifth, Baigent says.
- Aspirin therapy did not significantly lower stroke risk in the patients with no history of heart attack or stroke.
- Daily treatment with aspirin was associated with an increased risk for internal bleeding by a third in the primary prevention trials.
Aspirin therapy was found to prevent five nonfatal heart attacks for every 10,000 low-to-moderate-risk patients treated, while one extra bleeding-related stroke and three extra gastrointestinal bleeds occurred, Baigent says.
"On the basis of these findings, we don't believe that general guidelines advocating the routine use of aspirin in healthy people can be justified," he says.
Aspirin Guidelines
Baigent believes health policy groups that now recommend aspirin for primary prevention should revisit their treatment policies.
In its own guidelines for the primary prevention of heart attack and stroke, the American Heart Association states that the benefits of low-dose aspirin (75 to 160 milligrams/day) outweigh the risks in most patients "at higher coronary risk."
But the guidelines also state that aspirin should not be given to patients who are aspirin intolerant or to those at risk for gastrointestinal bleeding and bleeding-related stroke.
American Heart Association spokesman and cardiologist Gerald Fletcher, MD, tells WebMD that he believes these guidelines are sound and that the benefits of low-dose aspirin do outweigh the risks in healthy people with a low risk of bleeding who are at risk for having a first heart attack.
He points out that in one of the studies included in the analysis, participants took 500 milligrams of aspirin daily.
"That's a lot of aspirin," he says, adding that lower doses are much safer.
But in an editorial published with the analysis, stroke researcher and neurologist Ale Algra, MD, wrote that risk factors should not be the only consideration when determining whether otherwise healthy people should take a daily aspirin.
In an interview with WebMD, Algra noted that while some patients may accept the risks, others might not want to take an aspirin every day if there is no clear benefit.
"The question today is not whether to give aspirin, it is whether to give aspirin in addition to these other medications," Baigent says. "Statins and blood pressure medications can reduce the risk of primary heart disease by about 50% and they are very safe."
Fletcher agrees that the main focus of patients and their clinicians should be on keeping cholesterol and blood pressure under control.
"People with high cholesterol need to get on a statin long before they think about aspirin," he says.