Pharmacy deserts and health inequities in St. Louis City: a geospatial analysis of access disparities and determinants

Background: Pharmacy deserts, or areas lacking convenient access to pharmacies, can limit access to medications and reduce adherence. In U.S. cities, pharmacy deserts are disproportionately concentrated in racial/ethnic minority and low-income neighborhoods. This study examined the demographics and spatial distribution of pharmacy deserts in St. Louis City, Missouri, and their associations with sociodemographic and healthcare access determinants. Methods: Pharmacy deserts were defined as census tract block groups whose centroids were more than 1 mile from a pharmacy, or more than a half mile and located within a tract where at least 20% of households lacked vehicle access. Demographic and socioeconomic data came from the 2020 Decennial Census and the 2019–2023 American Community Survey. We assessed associations between block-group characteristics and pharmacy-desert status using chi-square tests; estimated prevalence ratios (PRs) with modified Poisson regression (log link) using robust standard errors clustered by census tract; and tested a race × income interaction with a cluster-robust Wald F test. Results: Among St. Louis City residents, 17.2% lived in pharmacy deserts. Black residents accounted for 80% of the pharmacy desert population, compared to 43% citywide. Pharmacy deserts were 9.53 times more prevalent in majority-Black block groups (prevalence ratio: 9.53; 95% CI: 3.17–28.6). Income significantly modified the race–desert association (cluster-robust Wald F(1, 103) = 4.53, p = 0.036; Table 3; Fig. 2). Within low-income census tracts, majority-Black block groups had over three times the prevalence of pharmacy deserts (PR = 3.23; 95% CI, 1.03–10.16; p = 0.045), whereas within high-income census tracts the disparity was larger (PR = 43.00; 95% CI, 5.08–364.21; p = 0.001) but imprecise given the small number of pharmacy deserts in higher-income areas. Lorenz curves showed that 90% of the pharmacy desert population was concentrated in just 28% of census tracts, most with Black populations exceeding 89%. Conclusion: Racial and socioeconomic spatial inequities are strongly associated with pharmacy desert prevalence in St. Louis City. These findings are guiding coordinated efforts between the City of St. Louis Department of Health and a community pharmacy to improve access and reduce inequities.