Choice of neighborhood scale affects associations between environmental attributes and health-related outcomes. This phenomenon, a part of the modifiable areal unit problem, has been described fully in geography but not as it relates to food environment research. Using two administrative-based geographic boundaries (census tracts and block groups), supermarket geographic measures (density, cumulative opportunity and distance to nearest) were created to examine differences by scale and associations between three common U.S. Census-based socioeconomic status (SES) characteristics (median household income, percentage of population living below poverty and percentage of population with at least a high school education) and a summary neighborhood SES z-score in an eight-county region of South Carolina. General linear mixed-models were used. Overall, both supermarket density and cumulative opportunity were higher when using census tract boundaries compared to block groups. In analytic models, higher median household income was significantly associated with lower neighborhood supermarket density and lower cumulative opportunity using either the census tract or block group boundaries, and neighborhood poverty was positively associated with supermarket density and cumulative opportunity. Both median household income and percent high school education were positively associated with distance to nearest supermarket using either boundary definition, whereas neighborhood poverty had an inverse association. Findings from this study support the premise that supermarket measures can differ by choice of geographic scale and can influence associations between measures. Researchers should consider the most appropriate geographic scale carefully when conducting food environment studies.
Bibliographical noteFunding Information:
The authors would like to thank Denise M. Hodo, Kristopher Corwin and Dr. Andrey Bortsov for assisting in the fieldwork related to the establishment of the food outlet database within our eight-county study region in South Carolina. The study was supported by award number R21CA132133 from the National Cancer Institute . The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Cancer Institute or the National Institutes of Health. T.L.B. conducted statistical analyses and developed the manuscript; D.E.P. provided geographic expertise; N.C. provided epidemiologic expertise; J.D.H. participated in acquisition of data, geocoded the data and conducted GIS-based data management; A.D.L. wrote the funding application, developed the study aims and assisted in preparing the manuscript. All authors reviewed, edited and approved the final manuscript.
© 2016 Elsevier Ltd.
Copyright 2016 Elsevier B.V., All rights reserved.
- Food environment
- Geographic scale
- Neighborhood boundaries
- Socioeconomic characteristics