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Does the Distance to the Nearest Pharmacy Affect Medication Adherence Rates Among Elderly Patients with Diabetes?

      Objectives

      The purpose of this study was to examine whether a relationship exists between adherence to oral anti-diabetic medications and distance to nearest community pharmacy among elderly patients with diabetes mellitus in Pennsylvania.

      Methods

      This cross-sectional study used data obtained from Pennsylvania’s Pharmaceutical Assistance Contract for the Elderly (PACE) programs’ database to identify enrollees and community (independent or chain) pharmacies operating in PA. The addresses of the enrollees’ residences and community pharmacies were geocoded as longitude and latitude coordinates. The straight-line distances using haversine formula were calculated (in miles) to determine the distance between the enrollee and each pharmacy in PA. The shortest distance was considered as the distance required for an elderly to visit the nearest pharmacy. Medication adherence was calculated as proportion of days covered (PDC) using prescription claims data for oral anti-diabetic medications. Enrollees receiving prescriptions via mail order were excluded from this study. Generalized linear model (GLM) using a gamma distribution and log link was applied to evaluate the relationship between medication adherence and distance to a nearest pharmacy, including other variables such as sex, age, annual household income, marital status, race and ethnicity.

      Results

      The study included11,848 elderly patients with diabetes mellitus enrolled in the PACE program in 2015. The median distance to nearest community pharmacy was 0.59 miles (IQR: 0.29 – 1.55). Of the study population, 62.8% and 37.2% lived less than a mile and more than a mile from a nearest community pharmacy, respectively. Females (PDC=0.83), divorced enrollees (PDC=0.84), White (PDC=0.84) and Hispanic (PDC=0.83) enrollees were more adherent to medications. GLM showed that there is no significant relationship between medication adherence and distance to a nearest community pharmacy (p-value = 0.112).

      Conclusions

      Adherence to oral anti-diabetic medications is not associated with the distance to nearest community pharmacy among elderly with diabetes mellitus in Pennsylvania.