Exposure to the green environment is associated with improved biomarker-based indices of health and aging in adults
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Background. Inadequate exposure to health-promoting natural environments exacerbates adverse effects of chronic stress and contributes to reduced life expectancy in disadvantaged populations. Biomarker-based composite indices of allostatic load, systemic inflammation, and biological aging enable quantitative assessment of pre-clinical health effects of environmental factors; these indices are known predictors of morbidity and mortality.
Methods. This observational study in 335 adults in the Raleigh-Durham-Chapel Hill metropolitan area in North Carolina measured biomarkers of immune, neuroendocrine, and metabolic functions in blood samples, and DNA methylation status in leukocytes from 117 of these individuals. Allostatic load and inflammation indices were calculated by summing biomarker values dichotomized at health or distribution-based cutoffs. Epigenetic age was calculated from DNA methylation data using previously published definitions.
Results. An interquartile range increase in tree cover within 500 m of residence was associated with 13% (2%; 23%) and 16% (4%; 27%) lower allostatic load and inflammation indices, respectively, and 1.8 (0.8; 2.7) years lower mean difference between epigenetic and chronological ages in individuals who spent at least 30 min outdoors daily, adjusting for demographic and behavioral data, obesity, chronic infections, and two-dimensional spline of geographic coordinates. In individuals with residential tree cover above the median, spending at least 3 hours outdoors daily was associated with 68% (52%; 83%) reduction in systemic inflammation compared to controls spending less than 30 minutes outdoors. This was not observed for low tree cover settings.
Conclusion. Residential greenness is inversely associated with allostatic load and epigenetic aging. This abstract does not represent EPA’s policy.