BACKGROUND Among urban residents, increased contacts with nature are associated with reduced morbidity and mortality. The concept of allostatic load, a biomarker-based composite measure of physiological dysregulation, can be applied to study subclinical benefits of exposure, and to elucidate pathways leading to improved health. OBJECTIVE This research explored associations between residential vegetated land cover and an allostatic load index calculated using the statistical distance measure known as Mahalanobis distance. METHODS This cross-sectional population-based study involved 186 adult residents of the Durham-Chapel Hill, North Carolina metropolitan area. Measures of tree and grass cover within 500 m of residence were derived from the U.S. Environmental Protection Agency's EnviroAtlas land cover database. Fifteen biomarkers of immune, neuroendocrine, and metabolic functions were analyzed in serum samples. Regression analysis was conducted using generalized additive models with thin-plate spline functions of geographic coordinates, adjusting for modelled traffic air pollution from local sources and sociodemographic covariates. RESULTS The second and third tertiles of distance-weighted tree cover were associated with 14% (95% Confidence Limits 20%; 8%) and 15% (21%; 8%) reduction in adjusted median allostatic load, respectively, compared to the first tertile. The same tertiles of tree cover were also associated with 0.16 (0.03; 0.76) and 0.04 (0.01; 0.35) adjusted odds ratios of having allostatic load index above the 90th percentile of the sample distribution. Grass cover was inversely correlated with tree cover and was not associated with reduced allostatic load. CONCLUSIONS Subclinical beneficial health effects of green spaces demonstrated in this study are consistent with reduced susceptibility to acute environmental and social stressors, and reduced risks of morbidity and mortality.

中文翻译：

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北卡罗莱纳州中部居民附近树木的覆盖面积更大，同化负荷降低。

背景技术在城市居民中，与大自然的接触增加与发病率和死亡率降低有关。恒定负荷的概念是一种基于生物标志物的生理失调综合指标，可用于研究暴露的亚临床益处，并阐明导致健康改善的途径。目的本研究探讨了居住植被的土地覆盖与使用统计距离量度（称为马哈拉诺比斯距离）计算的同化负荷指数之间的关联。方法这项基于人群的横断面研究涉及北卡罗来纳州都会区Durham-Chapel Hill的186名成年居民。从美国环境保护局的EnviroAtlas土地覆盖数据库中获得500 m住宅内树木和草木覆盖的测量值。免疫的15种生物标志物 分析血清样本中的神经内分泌和代谢功能。使用具有地理坐标的薄板样条函数的广义加性模型进行回归分析，并根据本地来源和社会​​人口统计学协变量对模型化的交通空气污染进行调整。结果距离加权树木覆盖率的第二个和第三个三分位数分别与调整后的中位数静力负荷相比分别降低了14％（95％置信限度20％； 8％）和15％（21％； 8％）。第一三分。树木覆盖率相同的三分位数也与0.16（0.03; 0.76）和0.04（0.01; 0.35）的已调整比值比相关，这些比值比具有高于样品分布的第90个百分位数的静态负载指数。草被覆盖率与树被覆盖率成反比，而与减少的静负荷无关。