Does Census-Tract-Level Fast-Food Availability Affect Colorectal Cancer Incidence? A U.S. State-Level Analysis

Background: Dietary choices may be associated with the risk of developing cancers. For example, higher consumption of red and processed meats has been associated with an increased incidence of colorectal cancer. The types of food available in an individual’s neighborhood may be influential in determining the diets of individuals. Individuals who have easier access to fast-food establishments may be more prone to have unhealthy diets and subsequently have a higher risk of developing colorectal cancer. Identification of possible associations between the food-related neighborhood environment and colorectal-cancer incidence may aid in identifying and implementing public health strategies and preventative clinical interventions aimed at reducing the incidence and mortality associated with colorectal cancer.

Objective: Explore the association between census-tract-level fast food availability and colorectal cancer incidence for Texas, which is the second largest state in the United States.

Method: Cancer data were provided by the Texas Cancer Registry, Cancer Epidemiology and Surveillance Branch, Texas Department of State Health Services, 1100 West 49th Street, Austin, TX 78756, https://www.dshs.texas.gov/tcr/. Individuals diagnosed with colorectal cancer were geocoded to the census-tract of their residence at the time of diagnosis. Individuals diagnosed between 2005 and 2009 were geocoded to the 2000 census-tract boundaries. Individuals diagnosed between 2010 and 2015 were geocoded to their 2010 census-tract boundaries. Colorectal cancer cases were aggregated to the census-tract level. Incidence (per 100,000 persons) was calculated by dividing the number of cases by the years of observation and census-tract populations Zip-code number of establishments were converted to census-tract estimates by using zip code to census-tract crosswalks available from the U.S. Department of Housing and Urban Development. Fast food density (per 100,000 persons) was calculated by dividing the number of establishments by total population of the census-tract. Covariates in the model were 2000 or 2010 census-tract level percent male, percent white, median age, percent renter occupied, median household income, percent individuals below poverty, percent of persons 25 years and older with an education of high-school or higher, and percent foreign born. Due to skewed distribution of incidence and fast-food were transformed using a natural log transformation. Ordinary least squares regression was used to analyze the association between census-tract fast-food density and incidence. Multicollinearity was assessed using variance inflation factor.

Results: Fast-food density was associated with colorectal cancer incidence (Years 2005-2009: β = 0.02816, p-value = 0.001; Years 2010-2015: β = 0.03526, p-value = <0.0001) after controlling for percent male, percent white, median age, percent renter occupied, median household income, percent individuals below poverty, percent of persons 25 years and older with an education of high-school or higher, and percent foreign born.

Conclusion: Higher fast-food density was associated with higher colorectal cancer incidence. Future observational studies should examine the role of area fast-food availability, individual diets, and colorectal cancer risk.