Antihypertensive Medication Adherence and Risk of Cardiovascular Disease Among Older Adults: A Population‐Based Cohort Study

Abstract

Background Antihypertension medication (antihypertensive) adherence lowers risk of cardiovascular disease ( CVD ); few studies have examined this association among older adults. Methods and Results We assessed this association among Medicare fee‐for‐service beneficiaries aged 66 to 79 years who were newly diagnosed with hypertension and initiated on antihypertensives in 2008–2009 (n=155 597). We calculated proportion of days covered ( PDC ) during follow‐up, using proportional subdistribution hazard models, to examine association between antihypertensive adherence and a composite CVD outcomes, including first incident of fatal/nonfatal acute myocardial infarction, ischemic heart disease, stroke/transient ischemic attack, and heart failure. During follow‐up (median 5.8 years and 798 621 person‐years), we documented 47 198 CVD events. Among beneficiaries, 60.8%, 30.3%, and 8.9% had PDC ≥80%, 40% to 79%, and <40%. Crude incidence of CVD events were 40.1 (95% CI, 40.0–40.1), 93.9 (93.8–93.9), and 98.1 (98.1–98.2) per 1000 person‐years for PDC ≥80%, 40% to 79%, and <40%, respectively. Adjusted hazard ratios for CVD events were 1.0 (<40% as reference), 1.0 (0.97–1.03) for 40% to 79%, and 0.44 (0.42–0.45) for ≥80% ( P <0.001). Dose‐response analysis suggested a nonlinear relationship between PDC and risk for CVD events with a protective effect of ≥80%. The pattern of associations between PDC and ischemic heart disease, stroke/transient ischemic attack, and heart failure were largely consistent as for CVD events and across different groups. Conclusions Antihypertensive adherence was associated with a significantly lower risk of CVD events among older adults. There appeared to be a threshold effect in reducing CVD events at around PDC 80%, above which the risk for CVD reduced substantially.