Methods/Statistics
Building an infrastructure to study longer-term, geospatial food access through residential history linkages Niyati Sudhalkar* Garth Rauscher Neng Wan
INTRODUCTION: Longer-term, cumulative geospatial access to food is an under-appreciated social determinant of health in cancer, given cancer’s typically long latency period. We provide an overview of methods we use to construct longer-term food environments for epidemiologic cancer incidence and survival studies. METHODS: Identifiers are submitted to LexisNexis for linkage to their proprietary residential histories (RH) database. RH data are cleaned using SAS programs provided by NCI. We assign a primary address for each calendar year of RH (1990-2020). Food outlet data from the National Establishment Time Series (NETS) Database for the US Census combined statistical area (CSA) 176 (Chicago- Naperville, IL-IN-WI) were obtained for 1990-2020. Using Standard Industrial Classification (SIC) codes, type of food industry, trade name, and company name, food outlets are divided into healthy (supermarkets, grocery stores, etc.) and less healthy food sources (fast-food outlets, convenience, and gas stations, etc.). After building the appropriate, decade-specific street networks from TIGER/line shapefiles using ESRI’s Network Analysis tool, we calculate driving (up to 5 miles) and walking (up to 1.5 miles) distances from each residence to each food outlet using the ESRI’s Network Analysis Origin-Destination Cost Matrix (ODOM) solver. We define food access scores as inverse-distance weighted walking and driving distances to food outlets. Year-specific scores are summed to define the four final measures of 30-year cumulative, longer-term driving, and walking distance access to healthy and less healthy food sources. RESULTS AND DISCUSSION: Geospatial measures of longer-term (30-year) food access – when linked in epidemiologic studies to participants’ residential histories – hold great promise for understanding how this crucial social determinant of health impacts cancer and other health conditions and for informing policy changes to make access to healthy food more equitable.