Importance: The unaffordability of drugs has been a persistent and elusive challenge in the US health care system. Little is known about the prevalence and persistence of cost-related medication nonadherence (CRN) in a population with high-cost, high-need resource utilization.

Objective: To evaluate the prevalence and persistence of CRN among Medicare beneficiaries at high risk of hospitalization as well as the characteristics associated with CRN in this population.

Design, Setting, and Participants: This cohort study used survey data from Medicare patients at high risk of hospitalization and with a life expectancy greater than 12 months at an urban academic medical center from November 6, 2012, to January 30, 2018. Patients were followed up for 12 months at 3-month intervals from baseline, for a total of 5 surveys. Data were analyzed from September 1, 2020, to January 5, 2021.

Main Outcomes and Measures: Self-reported CRN, using a metric of persistence and transiency. Based on the results of the 5 surveys, CRN was categorized as persistent (3 or more surveys), intermittent (2), transient (1), and any (1 or more). Multiple logistic regression analyses were used to evaluate factors associated with persistent and transient CRN.

Results: Of the 1655 Medicare beneficiaries followed up during the 15-month study period, 1036 (62.6%) were women and 1452 (87.7%) were Black or African American; 769 (46.5%) were younger than 65 years, and 886 (53.5%) were 65 years or older (mean [SD] age, 62.4 [15.9] years). A total of 374 patients (22.6%) reported CRN at baseline,810 (48.9%) reported any CRN, and 230 (13.9%) reported persistent CRN (148 [19.2%] of those younger than 65 years and 82 [9.3%] of those 65 years or older). The 230 patients who had persistent CRN accounted for 28% of those who reported CRN at least once during the 15-month study period. Younger age (eg, <50 years vs 75 years: adjusted odds ratio [AOR], 3.07; 95% CI, 1.61-5.86; P =.001), worse self-reported health (AOR, 1.59; 95% CI, 1.10-2.31; P =.01), and depression (AOR, 1.58; 95% CI, 1.11-2.24; P =.01) were associated with greater likelihood of persistent CRN. The population-adjusted prevalence of CRN was 53.6% (887 patients).

Conclusions and Relevance: The findings suggest that CRN is prevalent, moderately persistent, and variable in the Medicare population at high risk of hospitalization despite coverage by insurance. Longitudinal follow-up and refined predictive modeling of CRN appear to be needed to identify and target more precisely those with persistent CRN and to develop effective interventions.