Aspirin and healthy longevity within racial and ethnic minoritized older adults in the United States

Importance: The ASPREE randomized trial found no overall benefit of low-dose aspirin for disability-free survival among older adults. However, individual estimates in pre-specified subgroups indicated potential benefit among racial and ethnic minoritized participants in the United States (US). Objective: To evaluate whether the effect of low-dose aspirin vs placebo on disability-free survival differed across US Black and Hispanic ASPREE participants using individualized treatment-effect estimation. Design, Setting, and Participants: Post hoc clinical trial analysis of ASPREE, a randomized, double-blind, placebo-controlled clinical trial of daily low-dose aspirin vs placebo. This analysis included US ASPREE participants who self-identified as non-Hispanic Black or Hispanic, were aged 65 years or older, and had complete baseline predictor and outcome data. Interventions: Randomization to daily 100-mg aspirin or placebo. Main Outcomes and Measures: The primary outcome was loss of disability-free survival, defined as death, persistent physical disability, or dementia. Individualized treatment effects were estimated post hoc using a Random Survival Forest X-learner. Heterogeneity was evaluated on the relative scale with Cox proportional hazards models and on the absolute scale with 5-year risk differences. Results: Among 2411 US ASPREE participants, 1270 were included in the Black and Hispanic analytic cohort (897 non-Hispanic Black and 373 Hispanic participants; mean age, 71.8 years). Aspirin was associated with lower risk of disability-free survival loss compared with placebo (hazard ratio [HR], 0.65; 95% CI, 0.45-0.93). In model-derived tertiles, aspirin was associated with lower risk in the greatest predicted-benefit group (HR, 0.36; 95% CI, 0.19-0.71; 5-year absolute risk difference [ARD], -11.1 percentage points; 95% CI, -22.0 to -0.1) but not in the lowest predicted-benefit group (HR, 1.26; 95% CI, 0.70-2.27; ARD, +3.9 percentage points; 95% CI, -5.9 to 13.6). Conclusions and Relevance: In these analyses of US Black and Hispanic ASPREE participants, aspirin effects on disability-free survival appear to be heterogeneous, with benefit concentrated in a subset of participants. Because these findings are from post-hoc models, they should be externally validated before being incorporated into clinical decision-making. Trial Registration: ClinicalTrials.gov Identifier: NCT01038583; https://clinicaltrials.gov/study/NCT01038583