No sex-specific differences seen in effectiveness, safety of aspirin for secondary prevention

There are no significant sex-specific differences in the effectiveness and safety of aspirin (81 mg or 325 mg) for secondary prevention of atherosclerotic cardiovascular disease (ASCVD) events, an analysis of a randomized clinical trial found.

Researchers assessed sex-specific differences in patient outcomes using data from the Aspirin Dosing: A Patient-Centric Trial Assessing Benefits and Long-Term Effectiveness (ADAPTABLE) trial. The study was an open-label trial conducted at 40 medical centers that randomly assigned patients with chronic, stable ASCVD to 81 mg versus 325 mg of aspirin daily. Primary effectiveness outcomes included all-cause death and hospitalization for myocardial infarction (MI) or stroke, and the primary safety outcome was hospitalization for major bleeding requiring transfusion. Findings were published by JAMA Cardiology on July 10.

Between April 2016 and June 2019, 15,076 patients (median age, 67.7 years; 68.7% male) were followed for a median of 26.2 months. Of the 4,724 female patients, 2,307 (48.8%) received 81 mg of aspirin. Female participants were younger, less likely to self-report White race, more likely to smoke, and more likely to have a history of peripheral arterial disease. All-cause death and hospitalization for MI or stroke occurred in 379 female patients (8.1%) and in 780 male patients (7.1%).

Researchers found no significant interaction by sex for this end point between the aspirin doses. During follow-up, female participants had fewer revascularization procedures (adjusted hazard ratio [aHR], 0.79 [95% CI, 0.68 to 0.92]; P=0.002) but a significantly higher risk of hospitalization for stroke compared with male patients (aHR, 1.72 [95% CI, 1.27 to 2.33]; P<0.001). Female patients who received 81 mg of aspirin also had a slightly higher rate of bleeding than those who received the 325-mg dose (20 [0.83%] vs. 13 [0.52%]; aHR, 2.21 [95% CI, 1.04 to 4.70]). There were no significant sex differences regarding dose adherence.

One limitation to the analysis is that participants were not stratified by sex before randomization. In addition, the implications of study drug discontinuation and dose switching likely affected overall trial results, the researchers cautioned. Both sexes were more likely to discontinue or switch doses if they were initially randomized to 325 mg.

Overall, "there were no sex-specific differences in the primary effectiveness and safety end points of 2 different doses of aspirin for secondary prevention of ASCVD," the authors said. "Regardless of participant sex, ischemic and bleeding events were similar for 81mg and 325mg of daily aspirin."