Age and Aspirin Dosing in Secondary Prevention of Atherosclerotic Cardiovascular Disease

BACKGROUND

In patients with atherosclerotic cardiovascular disease, increasing age is concurrently associated with higher risks of ischemic and bleeding events. The objectives are to determine the impact of aspirin dose on clinical outcomes according to age in atherosclerotic cardiovascular disease.

METHODS AND RESULTS

In the ADAPTABLE (Aspirin Dosing: A Patient-Centric Trial Assessing Benefits and Long-Term Effectiveness) trial, patients with atherosclerotic cardiovascular disease were randomized to daily aspirin doses of 81 mg or 325 mg. The primary effectiveness end point was death from any cause, hospitalization for myocardial infarction, or hospitalization for stroke. The primary safety end point was hospitalization for bleeding requiring transfusion. A total of 15 076 participants were randomized to aspirin 81 mg (n=7540) or 325 mg (n=7536) daily (median follow-up: 26.2 months; interquartile range: 19.0-34.9 months). Median age was 67.6 years (interquartile range: 60.7-73.6 years). Among participants aged <65 years (n=5841 [38.7%]), a primary end point occurred in 226 (7.54%) in the 81 mg group, and in 191 (6.80%) in the 325 mg group (adjusted hazard ratio [HR], 1.23 [95% CI, 1.01-1.49]). Among participants aged ≥65 years (n=9235 [61.3%]), a primary end point occurred in 364 (7.12%) in the 81 mg group, and in 378 (7.96%) in the 325 mg group (adjusted HR, 0.95 [95% CI, 0.82-1.10]). The age-dose interaction was not significant (P=0.559). There was no significant interaction between age and the randomized aspirin dose for the secondary effectiveness and the primary safety bleeding end points (P>0.05 for all).

CONCLUSIONS

Age does not modify the impact of aspirin dosing (81 mg or 325 mg daily) on clinical end points in secondary prevention of atherosclerotic cardiovascular disease.

Comparative Effectiveness of Aspirin Dosing in Cardiovascular Disease

BACKGROUND

The appropriate dose of aspirin to lower the risk of death, myocardial infarction, and stroke and to minimize major bleeding in patients with established atherosclerotic cardiovascular disease is a subject of controversy.

METHODS

Using an open-label, pragmatic design, we randomly assigned patients with established atherosclerotic cardiovascular disease to a strategy of 81 mg or 325 mg of aspirin per day. The primary effectiveness outcome was a composite of death from any cause, hospitalization for myocardial infarction, or hospitalization for stroke, assessed in a time-to-event analysis. The primary safety outcome was hospitalization for major bleeding, also assessed in a time-to-event analysis.

RESULTS

A total of 15,076 patients were followed for a median of 26.2 months (interquartile range [IQR], 19.0 to 34.9). Before randomization, 13,537 (96.0% of those with available information on previous aspirin use) were already taking aspirin, and 85.3% of these patients were previously taking 81 mg of daily aspirin. Death, hospitalization for myocardial infarction, or hospitalization for stroke occurred in 590 patients (estimated percentage, 7.28%) in the 81-mg group and 569 patients (estimated percentage, 7.51%) in the 325-mg group (hazard ratio, 1.02; 95% confidence interval [CI], 0.91 to 1.14). Hospitalization for major bleeding occurred in 53 patients (estimated percentage, 0.63%) in the 81-mg group and 44 patients (estimated percentage, 0.60%) in the 325-mg group (hazard ratio, 1.18; 95% CI, 0.79 to 1.77). Patients assigned to 325 mg had a higher incidence of dose switching than those assigned to 81 mg (41.6% vs. 7.1%) and fewer median days of exposure to the assigned dose (434 days [IQR, 139 to 737] vs. 650 days [IQR, 415 to 922]).

CONCLUSIONS

In this pragmatic trial involving patients with established cardiovascular disease, there was substantial dose switching to 81 mg of daily aspirin and no significant differences in cardiovascular events or major bleeding between patients assigned to 81 mg and those assigned to 325 mg of aspirin daily. (Funded by the Patient-Centered Outcomes Research Institute; ADAPTABLE ClinicalTrials.gov number, NCT02697916.).