Low-dose aspirin may be used for primary prevention of cardiovascular disease (CVD) and colorectal cancer in adults aged 50 to 69 years, according to a newly released US Preventive Services Task Force (USPSTF) draft recommendation statement.
The USPSTF commissioned 3 separate systematic evidence reviews and a decision analysis model to develop its recommendation—an update of reviews published in 2007 and 2009—on aspirin use as a preventive method for CVD and colorectal cancer. The USPSTF also used a calculator derived from the 2013 American College of Cardiology/American Heart Association pooled cohort equations to estimate the risk for CVD thresholds, which predict patients’ 10-year risk for a hard atherosclerotic CVD event, defined as a nonfatal myocardial infarction, coronary heart disease event, or fatal or nonfatal stroke.
The evidence review focused on studies of primary CVD prevention. Researchers considered 11 randomized, controlled trials that evaluated the benefits of aspirin for the primary prevention of cardiovascular events. Of these studies, 4 were published after the original 2009 USPSTF review. The included trials had a total of 118 445 participants with mean age ranging from 55 to 65 years. Three trials were conducted exclusively with men; 1 was conducted exclusively with women. Eight trials used aspirin doses of 100 mg or less daily, and the duration of follow-up was 3 to 10 years.
Trial results consistently demonstrated the effectiveness of aspirin in preventing both myocardial infarction (MI) and stroke.
Analysis of 10 trials showed a 22% reduction in MI and coronary events. When the researchers restricted the pooled analysis to the 8 trials that used low-dose aspirin (100 mg daily or less), the reduction remained significant. The rate of nonfatal strokes was also reduced by 14% when only low-dose aspirin trials were included in the analysis.”
When researchers pooled 11 trials, they found a nonsignificant reduction in CVD mortality. Conversely, all-cause mortality risk was reduced by 6% in participants taking aspirin. A sensitivity analysis of the 8 trials with low-dose aspirin regimens resulted in similar findings.
Ultimately, the USPSTF found adequate evidence that a low-dose aspirin regimen may be of moderate benefit to reduce the risk for cardiovascular events, including nonfatal MI and stroke, in adults aged 50 to 69 years who are at an increased risk for CVD. The final magnitude of benefit varies by age and 10-year CVD risk. Evidence on aspirin use in those younger than 50 years or older than 69 years is insufficient, and the balance of benefits and harms cannot be determined, according to the USPSTF.
The task force also found adequate evidence that aspirin use in adults may lead to an increased risk for gastrointestinal bleeding and hemorrhagic stroke, although these risks vary based on preexisting individual risk. The USPSTF considers these potential harms to be “small to moderate” in adults aged 60 to 69 years and “small” in those aged 59 years or younger.
Before prescribing an aspirin regimen, physicians should perform a patient risk assessment for CVD including age, sex, race and ethnicity, total cholesterol level, high-density lipoprotein cholesterol level, systolic blood pressure, hypertension treatment, diabetes, and smoking. Physicians should encourage adults who have a high likelihood of benefit with little potential for harm to begin a long-term, low-dose aspirin regimen.
“There are a number of important research gaps that, if filled, could identify populations who may benefit from using aspirin to prevent CVD and colorectal cancer,” the USPSTF wrote. Additionally, the task force noted that “more information is needed to determine the interactions between statins and aspirin.”
- US Preventive Services Task Force. Draft Recommendation Statement: Aspirin to Prevent Cardiovascular Disease and Cancer. http://www.uspreventiveservicestaskforce.org/Page/Document/draft-recommendation-statement/aspirin-to-prevent-cardiovascular-disease-and-cancer. September 2015. Accessed October 26, 2015.