Long-Term Effectiveness of Acetylsalicylic Acid in Primary Prevention of Cardiovascular Diseases and Mortality in Patients at High Risk, a Retrospective Cohort Study—The JOANA Study

<b>Background/Objectives:</b> Although differences seem to exist by age in primary cardiovascular prevention with acetylsalicylic acid (ASA), direct comparisons are lacking, as are studies with real-world data. We sought to examine the effectiveness of ASA in reducing cardiovascular diseases and overall mortality in patients at high risk by age subgroups. <b>Methods:</b> We designed a retrospective cohort study using the database of the Catalan primary care system (SIDIAP), Spain, for the period 2006-2020. Included participants were high-cardiovascular-risk individuals without previous vascular disease. We considered people aged 40 to 59 and ≥60 years of age. We assessed the incidences of atherosclerotic cardiovascular disease (ASCVD), all-cause mortality, and ASA adverse effects using Cox proportional hazards modelling, adjusted by the propensity score of ASA treatment. <b>Results:</b> During the study period, 7576 and 30,282 people were aged 40 to 59 and ≥60 years, respectively. The median follow-up was 11.21 (10.71-11.54) years (40 to 59 year-olds) and 11.09 (10.55-11.54) years (≥60 year-olds). The hazard ratio of ASA use for ASCVD in the group aged 40-59 years was 0.64 (0.41-0.99). The number needed to treat in this group was 40 persons and the number that needed to harm for gastrointestinal bleeding (the only adverse effect with significant hazard ratio) was 75 individuals. <b>Conclusions:</b> This direct comparison of real-world age groups at high cardiovascular risk showed no benefit but increased risk in the older population (≥60 years). In the younger subgroup, our observations would support primary prevention with ASA with a consideration of the individual optimal risk-benefit.