Assessing temporal variation in food environments in low- and middle-income countries

Music City Center 

Changing food environments (FEs) influence diets, contributing to increased noncommunicable disease risk globally. FEs in low- and middle-income countries (LMICs) shift rapidly due to informal food vendors, who can be mobile or frequently change jobs. However, much LMIC FE research is cross-sectional, and research designs are needed to study temporal variation at varying scales in these settings. We introduce temporal transects, a method for assessing temporal variation in a FE metric by collecting data over time at fixed points. Using a rapid, observation-based tool, we conducted 48 transects at 12 locations along urbanization gradients around two cities in Kenya (6477 observations on food vendors). FE metrics were tested for within- and between-day variation using longitudinal models and time series methods. FE metrics followed different temporal patterns that varied significantly within and between days, along urbanization gradients, and across larger geographic scales. Ignoring these patterns in data collection or analysis can lead to bias. Temporal transects are a feasible method to capture short-term FE variability at small scales.

temporal transects

temporal variation

food environments

low- and middle-income countries

longitudinal study design

longitudinal models 

Section on Statistics in Epidemiology