Supermarket Proximity and Risk of Hypertension, Diabetes, and CKD: A Retrospective Cohort Study

Rationale & Objective: Living in environments with low access to food may increase the risk of chronic diseases. We investigated the associa-tion of household distance to the nearest super-market (as a measure of food access) with the incidence of hypertension, diabetes, and chronic kidney disease (CKD) in a metropolitan area of the United States.Study Design: Retrospective cohort study.Setting & Participants: 777,994 individuals without hypertension, diabetes, or CKD at base -line within the HealthLNK Data Repository, which contains electronic health records from 7 health care institutions in Chicago, Illinois.Exposure: Zip code-level average distance between households and nearest supermarket.Outcome: Incidence of hypertension, diabetes, and CKD based on presence of ICD-9 code and/ or blood pressure >= 140/90 mm Hg, hemoglobin A1c >= 6.5%, and eGFR < 60 mL/min/1.73m2, respectively. Analytical Approach: Average distance to near-est supermarket was aggregated from street-level metrics for 56 Chicagoland zip codes. The cumulative incidence of hypertension, diabetes, and CKD from 2007-2012 was calculated for each zip code in patients free of these diseases in 2006. Spatial analysis of food access and disease incidence was performed using bivariate local indicator of spatial association (BiLISA) maps and bivariate local Moran I statistics. The relationship between supermarket access and outcomes was analyzed using logistic regression.Results: Of 777,994 participants, 408,608 developed hypertension, 51,380 developed dia-betes, and 56,365 developed CKD. There was significant spatial overlap between average distance to supermarket and incidence of hy-pertension and diabetes but not CKD. Zip codes with large average supermarket distances and high incidence of hypertension and diabetes were clustered in southern and western neigh-borhoods. Models adjusted only for neighbor-hood factors (zip code-level racial composition, access to vehicles, median income) revealed significant associations between zip code-level average distance to supermarket and chronic disease incidence. Relative to tertile 1 (shortest distance), ORs in tertiles 2 and 3, respectively, were 1.27 (95% CI, 1.23-1.3 0) and 1.38 (95% CI, 1.33-1.43) for diabetes, 1.03 (95% CI, 1.02-1.05) and 1.04 (95% CI, 1.02-1.0 6) for hypertension, and 1.18 (95% CI, 1.15-1.21) and 1.33 (95% CI, 1.29-1.37) for CKD. Models adjusted for demographic factors and health insurance showed significant and positive association with greater odds of incident diabetes (tertile 2: 1.29 [95% CI, 1.26-1.33]; tertile 3: 1.35 [95% CI, 1.31-1.3 9]) but lesser odds of hypertension (tertile 2: 0.95 [95% CI, 0.94-0.97]; tertile 3: 0.91 [95% CI, 0.8 9-0.92]) and CKD (tertile 2: 0.80 [95% CI, 0.78-0.82]; tertile 3: 0.73 [95% CI, 0.72-0.76]). After adjusting for both neighborhood and individual covariates, supermarket distance remained significantly associated with greater odds of diabetes and lesser odds of hypertension, but there was no significant association with CKD.Limitations: Unmeasured neighborhood and so-cial confounding variables, zip code-level analysis, and limited individual-level information.Conclusions: There are significant disparities in supermarket proximity and incidence of hyper-tension, diabetes, and CKD in Chicago, Illinois. The relationship between supermarket access and chronic disease is largely explained by indi- vidual-and neighborhood-level factors.