Distance to supermarkets is a risk factor for CKD, hypertension, diabetes development
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Researchers identified the distance between a household and a supermarket as a risk factor for chronic kidney disease, hypertension and diabetes development.
Further, the correlation between supermarket access and chronic disease can be explained by individual and neighborhood-level factors.
In a retrospective cohort study, researchers reviewed data for 777,994 individuals in Chicago without hypertension, diabetes or CKD in 2006 to determine the average household’s distance to the closest supermarket in a zip code. Researchers defined supermarkets as a full-service store carrying a diverse line of groceries and with five or more checkout lanes.
Using street-level metrics for 56 Chicagoland zip codes, researchers calculated the average household distance to a supermarket. Additionally, researchers determined the average incidence of hypertension, diabetes and CKD between 2007 and 2012 for each zip code.
They used bivariate Local Indicator of Spatial Association maps and bivariate Local Moran I statistics to conduct spatial analyses of food access and disease incidence. To measure the relationship between supermarket access and incidence of hypertension, diabetes and CKD, researchers used logistic regression.
Among the patients who were disease-free in 2006, 408,608 developed hypertension, 51,380 developed diabetes and 56,365 developed CKD between 2007 and 2012. Although researchers identified a significant spatial overlap between average distance to supermarket and incidence of hypertension and diabetes, there was not with CKD.
The zip codes with high average supermarket distances and high incidences of hypertension and diabetes were grouped in southern and western neighborhoods of Chicago.
When adjusting for neighborhood factors, the correlation was significant between average zip code level distance to supermarket and incidence of hypertension, pre-diabetes and CKD. Models adjusted only for demographic factors and health insurance revealed a substantial and positive correlation between incident diabetes and pre-diabetes but a negative correlation with hypertension and CKD.
Researchers noted that after adjusting for both neighborhood and individual covariates, the association stayed significant and positive for diabetes and pre-diabetes, attenuated and became nonsignificant for CKD, and was negative for hypertension.
“We found that supermarket distance is a confounding marker for a number of other important individual factors like race, sex and age and neighborhood factors like income, racial composition and access to a vehicle,” Gaurang Garg, MD, from the department of medicine in the Feinberg School of Medicine at Northwestern University, and colleagues wrote.
To address disparities in food access, initiatives have been proposed but have shown various results.
“The fact that supermarket research has yielded such mixed results underscores the complexity of the problem at hand. Significant reduction in health disparities may require a greater breadth and depth of policies and interventions to improve more than just physical access to supermarkets, but also critical health-influencing social contexts like housing, education, capital investment and job creation,” Garg and colleagues wrote. They added, “Additional studies utilizing neighborhood deprivation indexes and hierarchical models may further elucidate the respective individual-level and neighborhood-level contribution to disease outcomes.”
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