Comparing Perception-Based and Geographic Information System (GIS)-Based Characterizations of the Local Food Environment

Abstract

Measuring features of the local food environment has been a major challenge in studying the effect of the environment on diet. This study examined associations between alternate ways of characterizing the local food environment by comparing Geographic Information System (GIS)-derived densities of various types of stores to perception-based measures of the availability of healthy foods. Survey questions rating the availability of produce and low-fat products in neighborhoods were aggregated into a healthy food availability score for 5,774 residents of North Carolina, Maryland, and New York. Densities of supermarkets and smaller stores per square mile were computed for 1 mile around each respondent's residence using kernel estimation. The number of different store types in the area was used to measure variety in the food environment. Linear regression was used to examine associations of store densities and variety with reported availability. Respondents living in areas with lower densities of supermarkets rated the selection and availability of produce and low-fat foods 17% lower than those in areas with the highest densities of supermarkets (95% CL, −18.8, −15.1). In areas without supermarkets, low densities of smaller stores and less store variety were associated with worse perceived availability of healthy foods only in North Carolina (8.8% lower availability, 95% CL, −13.8, −3.4 for lowest vs. highest small-store density; 10.5% lower 95% CL, −16.0, −4.7 for least vs. most store variety). In contrast, higher smaller store densities and more variety were associated with worse perceived healthy food availability in Maryland. Perception-and GIS-based characterizations of the environment are associated but are not identical. Combinations of different types of measures may yield more valid measures of the environment.KEYWORDS Environment, Neighborhoods, Food, GIS, Survey assessment.Several studies have linked local food environments to diet quality, 1-11 although the extent to which these associations reflect causal processes remains a topic of research. A major challenge in this work has been developing valid and reliable measures of the local food environment. Many studies have characterized food environments by counting the number of certain types of stores (usually supermarkets) in the census tracts or zip codes in which study participants live. [12][13][14][15][16] This approach relies on the assumptions that only supermarkets offer an array of healthy foods and that the range and quality of healthy foods offered by supermarkets are invariant over space.

Access to Healthful Foods among an Urban Food Insecure Population: Perceptions versus Reality

“…15,16 The most common method for assessing local food environments involves a process of counting food stores and then geographically anchoring the stores in space using geographic information system (GIS) software; this method typically involves food store identification through existing commercial databases and address books. [17][18][19][20] Limitations related to this method include the risk of misidentification of food stores in the commercial database, store closure between the creation of the data source and mapping, and GIS mapping errors.…”

“…24 Limited efforts have been made to assess perceptions of food access. 15,25,26,27 A three-item scale was developed by Moore and colleagues to assess perceived availability of healthy foods within a 1-mi radius (20-min walk) of participants' residence. 15 Perceived availability of access to healthy foods was then compared to actual access to supermarkets and other smaller food stores identified through InfoUSA®, a comprehensive commercial database of businesses in the US.…”

“…15,25,26,27 A three-item scale was developed by Moore and colleagues to assess perceived availability of healthy foods within a 1-mi radius (20-min walk) of participants' residence. 15 Perceived availability of access to healthy foods was then compared to actual access to supermarkets and other smaller food stores identified through InfoUSA®, a comprehensive commercial database of businesses in the US. This study found that participants living in areas of low supermarket density rated their perceived availability of healthy foods 17% lower than those living in areas with the highest densities of supermarkets.…”

Perceived and objective measures of the food store environment and the association with weight and diet among low-income women in North Carolina

“…Widespread recognition of the relationship between the built environment, health status and food choices has led to growing interest in measuring aspects of the food store environment (8)(9)(10)(11)(12)(13)(14)(15) . However, few studies have examined both subjective (16,17) and objective measures of the food store environment and their association with weight and diet quality (7,(17)(18)(19)(20)(21)(22) . Perceived and objective measures each provide unique data that, taken together, can elucidate important factors operating at both the individual and the neighbourhood level.…”

“…Simultaneous consideration of both types of measure has the potential to establish a broader context for understanding the environmental determinants of obesity (16) .…”