Tree canopy cover and injurious pedestrian falls: a location-based case-control study

Despite about half a million injurious pedestrian falls occurring annually in the United States, prevention of pedestrian falls is under studied. Sidewalk damage from street trees is a known risk for falls; however, tree canopy cover might reduce falls in summer months by lowering ambient temperatures. We conducted pilot research to assess whether emergency medical services (EMS) data could be used to implement a multi-city, location-based case-control study investigating the association between tree canopy cover and locations of injurious pedestrian falls. Case locations (n = 497) were places where EMS responded to a pedestrian fall occurrence between April and September of 2019. Matched control locations (n = 994) were selected from intersections, street segments, and ramp segments that existed in 2019. Percent tree canopy cover was measured within a 100-m radial buffer of each location. Median tree canopy coverage at fall locations was 8%, compared to 14% for control locations. In adjusted analyses, higher tree canopy cover was inversely associated with fall locations (adjusted OR across the inter-quartile range of canopy cover = 0.57; 95% CI, 0.45-0.74), suggesting higher tree canopy cover is associated with lower pedestrian falls risk. Methodological challenges and solutions to implementing and interpreting the location-based, case-control design with EMS data are discussed.