Greater Residential Tree Cover Is Associated with Reduced Stress-Related Physiological Dysregulation in Residents of Central North Carolina

Background: Urban green spaces have been linked to reduced morbidity and mortality. Alleviation of chronic stress is a hypothesized mechanism of these salutogenic effects. Our previous research showed that greater residential greenness was associated with lower allostatic load suggesting reduced physiologic dysregulation. The objective of this analysis was to assess the effects of different vegetation types on the distribution of allostatic load values.Methods: This cross-sectional study involved 186 adult residents of the Durham-Chapel Hill, NC urban area. High-resolution metrics of tree and grass cover within 500 m of each residence were produced using US EPA EnviroAtlas database. Weighted tree cover measures were produced allowing for an exponential decay of effect with distance from residence. Serum samples were tested for fifteen biomarkers of neuroendocrine, metabolic, and immune functions. Allostatic load was estimated as a standardized distance from the center of a joint multivariate distribution of biomarkers (Mahalanobis distance). Statistical analysis involved two stages: (1) generalized additive regression models of allostatic load on socio-demographic covariates and a thin plate smoothing function of geographic coordinates; and (2) quantile regression of residuals from the 1st stage on a weighted proportion of tree or grass cover.Results: Individuals in the 3rd tertile of tree cover distribution compared to individuals in the 1st tertile had 8% (1%; 15%), 12% (4%; 20%), and 23% (12%; 33%) lower predicted values of the 50th, 75th, and 90th percentiles of the marginal distribution of allostatic load respectively. Grass cover was not a significant predictor of allostatic load.Conclusions: Trees near residence may help to alleviate chronic stress preventing stress-related physiological dysregulation (allostatic load). Health benefits may be stronger in individuals with greater chronic stress. This abstract does not represent EPA policy.