Out‐of‐Pocket Costs and Antihypertensive Medication Use Among Veterans: A Natural Experiment

Background: Blood pressure (BP) control remains suboptimal in the United States despite available low‐cost antihypertensive medications. Even small out‐of‐pocket medication costs may contribute to adherence. We determined whether $0 versus >$0 out‐of‐pocket costs for antihypertensive medications is associated with differences in adherence, discontinuation, BP control, and cardiovascular outcomes. Methods: We included veterans with newly diagnosed hypertension who initiated antihypertensive medication in the Veterans Health Administration from 2004 to 2022. A fuzzy regression discontinuity design with 2‐stage residual inclusion leveraged differences in medication copay policy at a 50% service‐connected disability threshold (≥50% service‐connected disability: $0 out‐of‐pocket cost versus <50%: $8 monthly cost). Outcomes included 1‐year medication nonadherence (proportion of days covered <80%), 1‐year medication discontinuation (no medication in the final 90 days of the study year), 1‐year BP control (systolic BP/diastolic BP <140/90 mm Hg and <130/80 mm Hg) and cardiovascular disease events (myocardial infarction, coronary revascularization, peripheral artery disease, or stroke). Results: Among 417 705 veterans (mean±SD age, 56 [13] years; 92% male; 61% non‐Hispanic White), 296 432 (71%) had $0 out‐of‐pocket costs. Accounting for changes in eligibility for $0 copays at the 50% service‐related disability threshold, $0 out‐of‐pocket costs were associated with lower odds of nonadherence (odds ratio [OR], 0.87 [95% CI, 0.81–0.94]) and medication discontinuation (OR, 0.77 [95% CI, 0.71–0.84]). One‐year BP control <140/90 mm Hg or <130/80 mm Hg and cardiovascular disease events events were similar between groups. Conclusions: Among veterans with newly diagnosed hypertension, modest out‐of‐pocket medication costs were associated with lower adherence and discontinuation. These findings can inform ongoing discussions regarding policy levers for improving hypertension outcomes.