An epidemic of childhood asthma has been documented around the world1 and within the USA. The exact cause of the increase remains elusive, but prevailing theories cite changes in the environment, indoors and outdoors, and changes in lifestyle as potential causes for the increase in the prevalence of asthma.Racial, ethnic and socioeconomic disparities in asthma are substantial, with an especially high prevalence of asthma in poor urban communities.
In the USA, a disproportionate part of the recent increase in the prevalence of asthma has been observed in the inner cities,which has contributed to its geographical variation. For example, early childhood prevalence of asthma is three times higher in the East Harlem area of New York City than in the adjacent but more affluent Upper East Side area. The aim of this study was to see if children living in areas with more strees have lower prevalence of asthma.
Street tree density was high in the most densely populated areas and in areas with less poverty, and was negatively correlated with the two measures of asthma burden . Higher street tree density was associated with a lower prevalence of childhood asthma even after adjustment for potential confounders (including sociodemographic characteristics, population density and proximity to pollution sources), but the association between street trees and hospitalisations as a result of asthma was no longer significant after adjustment.