Children living in areas with more street trees have lower asthma prevalence
- Received 1 November 2007
- Accepted 25 February 2008
- Published Online First 1 May 2008
Introduction: Childhood asthma prevalence in the US increased by 50% from 1980 to 2000, with especially high prevalence in poor urban communities.
Methods: Asthma prevalence among children ages 4-5 years old and asthma hospitalizations among children less than 15 years old were available for 42 health service catchment areas within New York City. Street tree counts were provided by the New York City Department of Parks and Recreation. We also measured proximity to pollution sources, socio-demographic characteristics, and population density for each area.
Results: Controlling for potential confounders, an increase in tree density of one standard deviation (SD: 343 trees/km2) was associated with a lower asthma prevalence (relative risk [RR]: 0.71 per SD of tree density; 95% CI [confidence interval]: 0.64-0.79), but not asthma hospitalizations (RR: 0.89 per SD of tree density; 95% CI: 0.75-1.06).
Conclusions: Street trees were associated with a lower prevalence of early childhood asthma. Our study does not permit inference that trees are causally related to asthma at the individual-level. The PlaNYC sustainability initiative, which includes a commitment to plant one million trees by the year 2017, offers an opportunity for a large prospective evaluation.