Medication Nonadherence: The Role of Cost, Community, and Individual Factors.

Objective: To explain the association of out-of-pocket (OOP) cost, community-level factors, and individual characteristics on statin therapy nonadherence.

Data Sources: BlueCross BlueShield of Texas claims data for the period of 2008-2011.

Study Design: A retrospective cohort of 49,176 insured patients, aged 18-64 years, with at least one statin refill during 2008-2011 was analyzed. Using a weighted proportion of days covered ratio, differences between adherent and nonadherent groups are assessed using chi-squared tests, t-tests, and a clustered generalized linear model with logit link function.

Principal Findings: Statin therapy adherence, measured at 48 percent, is associated with neighborhood-level socioeconomic factors, including race/ethnicity, educational attainment, and poverty level. Individual characteristics influencing adherence include OOP medication cost, gender, age, comorbid conditions, and total health care utilization.

Conclusions: This study signifies the importance of OOP costs as a determinant of adherence to medications, but more interestingly, the results suggest that other socioeconomic factors, as measured by neighborhood-level variables, have a greater association on the likelihood of adherence. The results may be of interest to policy makers, benefit designers, self-insured employers, and provider organizations.