An analysis of new data concluded that aspirin may not be an effective prevention strategy for cardiovascular disease and cancer.
The study authors pointed out that recent research does not appear to support the claim derived from older data that aspirin is effective in prevention. Therefore, they sought to “compare benefits and harms of aspirin for primary prevention before and after widespread use of statins and colorectal cancer screening.”
According to a press release on the findings, “Nearly half of adults 70 years and older have reported taking aspirin daily even if they don’t have a history of heart disease or stroke. Overall, an estimated 40% of adults in the United States take aspirin for primary prevention of cardiovascular diseases, making it one of our most commonly used medications.”
For the current analysis, the researchers compared two sets of data from studies evaluating aspirin for primary prevention: data from studies that recruited patients from 2005 onward, and previous individual patient data (IPD) meta-analyses that recruited patients between 1978 and 2012. They synthesized the current data using random-effects models. Outcomes included vascular (major adverse cardiovascular events [MACE], myocardial infarction [MI], and stroke), bleeding, cancer, and mortality outcomes.
IPD analyses of older aspirin studies encompassed 95,456 total patients evaluated for cardiovascular prevention and 25,270 for cancer mortality. There were four contemporary aspirin studies encompassing 61,604 total patients. The relative risks (RRs) for vascular outcomes for older versus newer studies were: MACE, 0.89 (95% confidence interval [CI], 0.83-0.95) vs. 0.93 (95% CI, 0.86-0.99); fatal hemorrhagic stroke, 1.73 (95% CI, 1.11-2.72) vs. 1.06 (95% CI, 0.66-1.70); any ischemic stroke, 0.86 (95% CI, 0.74-1.00) vs. 0.86 (95% CI, 0.75-0.98); any MI, 0.84 (95% CI, 0.77-0.92) vs. 0.88 (95% CI, 0.77-1.00); and non-fatal MI, 0.79 (95% CI, 0.71-0.88) vs. 0.94 (95% CI, 0.83-1.08). Newer studies did not observe a large decrease in cancer mortality (RR=1.11; 95% CI, 0.92-1.34). A significant increase was observed in major hemorrhage (older studies RR=1.48; 95% CI, 1.25-1.76 vs. newer studies RR=1.37; 95% CI, 1.24-1.53). No impact was observed on all-cause mortality, cardiovascular mortality, fatal stroke, or fatal MI.
The results of the study were published in Family Practice.
The study authors stated in summary, “Per 1200 persons taking aspirin for primary prevention for 5 years, there will be 4 fewer MACEs, 3 fewer ischaemic strokes, 3 more intracranial haemorrhages and 8 more major bleeding events. Aspirin should no longer be recommended for primary prevention.”