ILLUSTRATIVE CASE
A 55-year-old man with well-controlled diabetes, hypertension, and sleep apnea arrives at your office for a routine annual physical. In reviewing his medications, you note that he takes a low-dose aspirin daily for “heart health.” He has no known cardiovascular disease (CVD). His calculated 10-year risk of a major cardiovascular event is 11%.
Should this patient continue taking a daily aspirin for primary prevention of CVD?
Many patients in the United States take aspirin for primary prevention of CVD as recommended by the US Preventive Services Task Force (USPSTF).2 This recommendation was based on older studies of populations in which smoking rates were higher and statin use was less common, leading to an overall higher risk of CVD.3 (The USPSTF is currently in the process of updating its recommendation.) More recent RCTs have been done in patients with a lower baseline risk of CVD, and these outcomes are more generalizable to today’s population. This new meta-analysis includes recent RCTs that evaluated whether there is value in using aspirin for the primary prevention of CVD.
STUDY SUMMARY
No reduction in risk, increased chance of bleeding
Mahmoud and colleagues conducted a meta-analysis of 11 randomized controlled trials that included 157,248 patients and assessed the efficacy and safety of aspirin for primary prevention of cardiovascular events.1 The mean age of the total population was 61.3 years; 52% were women and 14% were smokers. The doses of aspirin used in most of the studies were ≤ 100 mg/d, although 2 of the studies examined doses that were higher. Patients were followed for a mean of 6.6 years. The primary efficacy outcome was all-cause mortality, and the primary safety outcome was major bleeding (as defined by each study). The secondary outcomes included cardiovascular mortality, fatal and nonfatal myocardial infarction (MI), and fatal and nonfatal ischemic stroke.
Aspirin did not lower all-cause mortality (risk ratio [RR] = 0.98; 95% confidence interval [CI], 0.93-1.02) and was associated with an increased risk of major bleeding (RR = 1.47; 95% CI, 1.31-1.65; number needed to harm = 250) and intracranial hemorrhage (RR = 1.33; 95% CI, 1.13-1.58). Aspirin also had no effect on all-cause mortality in subgroup analyses of patients with diabetes mellitus or high cardiovascular risk (10-year risk > 7.5%). There was (again) an increased risk of major bleeding.
Aspirin had no effect on the secondary outcomes—with the exception of the incidence of MI (RR = 0.82; 95% CI, 0.71-0.94; number needed to treat = 333). However, this outcome was associated with considerable heterogeneity (I2 = 67%), and the reduction was no longer evident after limiting the analysis to the more recent trials.
WHAT’S NEW?
Study is emblematic of a shift away from daily aspirin
Review of current guidelines and studies regarding the use of aspirin for primary prevention of CVD shows that the tide has been turning against this practice, but the change has been gradual. Newer studies—large RCTs such as ARRIVE (Aspirin to Reduce Risk of Initial Vascular Events) and ASCEND (A Study of Cardiovascular Events iN Diabetes)—found no mortality benefit (all-cause or cardiovascular) from using aspirin in this context.
Continue to: The USPSTF guidelines...
