A GPS-Based Methodology to Analyze Environment-Health Associations at the Trip Level : Case-Crossover Analyses of Built Environments and Walking
Environmental health studies have examined associations between context and health with individuals as statistical units. However, investigators have been unable to investigate momentary exposures, and such studies are often vulnerable to confounding from, for example, individual-level preferences. We present a Global Positioning System (GPS)-based methodology for segmenting individuals' observati