Friday, March 5, 2010
Earlier this week, the research article, “Aspirin for Prevention of Cardiovascular Events in a General Population Screened for a Low Ankle Brachial Index (ABI)”, was published in JAMA. The goal of the study was to determine if daily aspirin reduced the risk of heart attack and stroke in patients with a low ABI, a quick and inexpensive way to establish risk for these events, and no other risk factors. Researchers hoped to show that the ABI could identify asymptomatic higher risk individuals that could benefit from preventive treatments, such as aspirin use.
The researchers found that aspirin was not effective in preventing first heart attack, stroke, or other cardiovascular events for individuals with low ABI and an absence of other risk factors. However, due to the fact that ABI was the only indicator used when determining risk, the study population was ultimately found to be at very low risk for heart attack and stroke. According to current guidelines, this low risk group would not be encouraged to use aspirin. So the study may actually say more about ABI or the range of ABI as a screening tool for cardiovascular risk than aspirin for primary prevention of cardiovascular events.
Other issues with the study include adherence to the therapy and disproportionate number of females in the study. Interestingly, the study showed no statistically significant difference between the aspirin and control groups for bleeding. Recently, aspirin use for primary prevention has been questioned due to a potential increased risk for gastrointestinal and intracranial bleeding; this study shows that bleeding events were similar between aspirin and non-aspirin users.
Ultimately, this study shows that ABI or the ABI threshold measurement used (0.95) is not enough to predict higher risk of heart attack and stroke on a population level. Future studies with more participants, improved compliance rates, a more equitable distribution of males and females, and a lower level of ABI for study inclusion are necessary to shed more light on this issue. An editorial, also published in JAMA, further explains the potential limitations of the study. Although at first glance this article appears to be another critique on aspirin for primary prevention-as many media outlets suggested- the current American Heart Association and United States Preventive Services Task Force guidelines for aspirin use to prevent first heart attacks and strokes should still be followed. And, as they recommend, those considering aspirin should talk to their health care provider to determine if aspirin is right for them.
Program Associate, Partnership for Prevention