Medication Refill Adherence and Mortality Risk in the Oldest-Old:

Abstract Background The U.S. population aged 85 and older is growing rapidly, yet little research explores how medication refill adherence affects mortality in this group. Adherence is critical for managing hypertension and reducing cardiovascular risk, but missed refills may signal broader health, cognitive, or social issues beyond non-compliance. Objective This study examines the link between medication refill adherence and all-cause mortality in Medicare beneficiaries aged 85+ with hypertension. Design, Setting, and Participants: This retrospective cohort study analyzed Medicare claims data (2006–2021), using a 5% sample (2006–2016) and a 20% sample (2017–2021) of beneficiaries aged 85+ with confirmed hypertension. Exposure Refill patterns for antihypertensive drugs, statins, and proton pump inhibitors (PPIs) were evaluated via prescription claims, categorizing participants into regular vs. missed refill periods. Outcome Measure All-cause mortality was the primary outcome, with mortality risk compared between refill patterns using Cox proportional hazards models with time-varying exposure. Results Regular antihypertensive refills were linked to a 55-66% lower mortality risk (HR: 0.336–0.451), consistent even in those aged 95 + (HR: 0.366–0.441). Similar mortality reductions were seen with statins and PPIs, suggesting refill adherence reflects overall health stability rather than antihypertensive effects alone. Conclusion Missed refills strongly predict higher mortality in the oldest-old, likely indicating cognitive decline, frailty, or social vulnerability rather than purely pharmacologic factors. Pharmacy refill data could serve as an early-warning tool to identify at-risk older adults for targeted interventions. Further studies should investigate causal pathways and policy implications.