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CHD Risk Should Affect Decision on Aspirin Therapy

Kate Traynor

A national task force has suggested that a patient's risk of coronary heart disease and personal preference figure into the decision on whether to take aspirin to prevent an initial myocardial infarction or stroke.

According to the U.S. Preventive Services Task Force (USPSTF), the benefits of aspirin therapy seem to outweigh the risks for men over age 40 and for postmenopausal women, groups that are at increased risk for coronary heart disease. Younger people who smoke or have hypertension, diabetes mellitus, or another condition that increases the risk of "cardiovascular events" may likewise benefit from primary aspirin therapy.

USPSTF found in its review of the literature that the benefits of aspirin therapy for the primary prevention of cardiovascular events most clearly offset the hazards of aspirin use among people whose five-year risk for heart disease was at least 3 percent. The main risks associated with aspirin use were gastrointestinal bleeding and hemorrhagic stroke.

The recommendations and a research summary on which the recommendations were based appear in the Jan. 15 Annals of Internal Medicine. (The documents are also available at the Agency for Healthcare Quality and Research Web site.)

USPSTF suggests that clinicians discuss aspirin therapy with their "middle-aged and older" patients every five years or so, or when a new risk factor for cardiovascular disease is detected. The task force acknowledged that patients will differ in their views of the importance of the adverse events associated with aspirin use and in their aversion to a future cardiovascular event. Patients' preferences must therefore be considered when clinicians decide whether to start aspirin therapy.

The task force found that an aspirin dosage of 75 mg/day seemed to be as effective as higher ones but noted that the "optimum dose of aspirin for chemoprevention is not known."

In making its recommendations, USPSTF relied on data obtained from a meta-analysis of five large studies that assessed the ability of aspirin to prevent primary cardiovascular events in people with no history of cardiovascular disease.

Overall, aspirin use decreased the frequency of death from all causes by 7 percent and reduced study participants’ overall risk of myocardial infarction by 28 percent. But aspirin use increased, by 40 percent, the likelihood that a person would have a hemorrhagic stroke and raised, by 70 percent, a patient’s risk of "major" gastrointestinal bleeding.

An unrelated meta-analysis, which was published in the Jan. 12 BMJ (PDF), examined antiplatelet therapy, including aspirin use, for the prevention of cardiovascular events in patients at high risk for such events. The research team found that aspirin 75–150 mg/day should be routinely considered a preventive therapy for all people with a 2 percent or greater annual risk of "occlusive vascular events." For most healthy adults, however, daily aspirin therapy "may well be inappropriate," according to the researchers.

A noteworthy recommendation made by this research group was to administer a "loading dose" of at least 150 mg of aspirin to patients seeking treatment for an acute myocardial infarction. The meta-analysis did not, however, describe the clinical basis on which this recommendation was made.