describes the characteristics of the study tracts by neighborhood race categories. A total of 175 census tracts were included in our analysis, of which, eighty-three were classified as predominately African-American tracts and ninety-two were coded as mixed racial tracts. African-American tracts, on average, had greater population density and lower mean household incomes. More households lived in poverty in African-American tracts and fewer owned cars. provides basic descriptive statistics on the food access variables. On average, food environments had far more small food stores and convenience stores than supermarkets. In addition, food environments had a much greater aggregate amount of snack food shelf space than space dedicated to fruits and vegetables. African-American tracts, on average, had a higher number of stores for all store types except supermarkets; these bivariate differences with mixed-racial tracts were statistically significant for small food stores and general merchandise stores (results not shown).
Characteristics of census tracts by racial composition, New Orleans, LA, 2004-2005
Descriptive statistics on food access variables, New Orleans, LA, 2004-2005
presents results from the Poisson models that assessed the count of each food store type in the food environment by neighborhood racial composition, and controlled for population density. Supermarkets were less likely to be located in the food environments of predominately African-American tracts as compared to the environments of mixed racial tracts, with an Incident Rate Ratio (IRR) of 0.64, and a 95% Confidence Interval ranging from 0.49 to 0.83. Conversely, 1.6 times as many general merchandise stores (IRR 1.58, 95% CI 1.10 – 2.26) were found in African-American food environments. The finding of a higher number of small stores in African-American tracts, seen in bivariate results, was no longer significant when controlling for population density.
Incidence rate ratios of food stores for African-American census tracts, New Orleans, LA, 2004-2005 a
African-American food environments had significantly less aggregate shelf space dedicated to fresh fruits and fresh vegetables (). These areas had 19.7 meters less fresh fruit and 27.3 meters less fresh vegetable aggregate shelf space as compared to mixed racial areas. African-American environments also had significantly less frozen fruits and vegetables. These areas had nearly one meter less of frozen fruits and 12.4 meters less of frozen vegetables. Canned fruits and canned vegetables did not vary significantly by racial composition, nor did the aggregate availability of energy-dense snacks foods.
Subsequent analyses were conducted to test how sensitive our results were to our definition of African-American neighborhoods, based on 80% or more of the tract population. We also tested different thresholds, such as 50%, 60%, and 70%, and these produced similar findings as above (results not shown).