Abstract
BACKGROUND AND AIM: Greenness has been associated with lower risks of cardiovascular diseases, diabetes, cancer, and mortality among urban residents. Under the biophilia hypothesis, nature confers health benefits, but the underlying biological mechanisms need to be better elucidated. METHODS: This study investigates the associations between contemporary Normalized Difference Vegetation Index (NDVI) and urinary oxidative stress in participants residing in an urban district (Haidian) and a peri-urban district (Pinggu) of Beijing (N=251). Our outcome measurements are urinary creatinine-normalized concentrations of three oxidative stress biomarkers (free, total MDA, and 8-OHdG). Due to right skew of biomarkers data, they were ln-transformed. We calculated contemporaneous greenness level of winter 2016 and summer 2017 by the average daily satellite-derived NDVI in the zone with 500m*500m grids through Google Earth Engine (GEE). Linear mixed-effects models adjusted for demographic characteristics, morbidity, and environment covariates were used to explore associations of NDVI and the biomarkers. RESULTS:Baseline mean free MDA, total MDA and 8-OHdG were 1600.11 ng/ml, 11126.16 ng/ml, and 4.68 ng/ml, respectively. Individuals who live in greener areas tended to have lower levels of oxidative stress. Compared to the participants in the lowest NDVI tertile (0.11-0.25), those in the highest tertile (0.36-0.83) had significantly lower free and total MDA levels, with the decreased mean (95%CI) percentage of -21.32% (-38.91%, -2.38%) and -20.06% (-35.06%, -3.92%), respectively, (p = 0.020). In the urban participants, we found significant negative associations of NDVI with free MDA (p = 0.003), total MDA (p = 0.005), 8-OHdG (p = 0.020), but not in the peri-urban participants. CONCLUSIONS:Even within the same city, the protective effects of greenness on oxidative stress were more evident for urban residents. Considering that oxidative stress is a pathophysiologic risk factor for many diseases and natural aging, this research provides mechanistic insights on health benefits of green space in built environment and urban planning process. KEYWORDS: Greenness, oxidative stress, Malondialdehyde(MDA), 8-hydroxy-2 deoxyguanosine(8-OHdG)
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