Association between neighborhood greenspace and fasting plasma glucose from a large cohort study in Taiwan

Abstract

Growing evidence suggests that greenness exposure improves health status, but few studies address diabetes, and research mainly comes from Western countries. This study hypothesizes that higher greenness exposure benefits glucose control with increased intensity of physical activity. We used data from a longitudinal health examination database in Taiwan during 2000-2014. The normalized difference vegetation index (NDVI) was used as an objective indicator of greenness in the neighborhood. Fasting plasma glucose served as an indicator of early diabetes diagnosis. A metabolic equivalent value (MET) based on a compendium of physical activities was used to estimate the intensity of physical activity. We applied a linear mixed-effect model with an individual-level random effect to investigate the relationship between neighborhood greenness and the fasting plasma glucose value stratified by four levels of physical activity. There are 341,211 participants with no diabetes, and 773,602 check-up visits included here. The fasting glucose among participants living in areas with higher green space was lower than that of those living in less green areas. The beneficial effects of greenspace on glucose were stronger for those with more physical activity, especially in the 500-m buffer. In the physically inactive group, compared with the lowest quantile (Q1) of cumulative average greenness, people living in the highest quantile (Q4) of greenness had 0.35 mg less glucose in each dl of plasma [95% confidence interval: -0.50, - 0.20]. In the physically active group, people residing in the highest quantile (Q4) of greenness had 0.48 mg less glucose in each dl of plasma [95% confidence interval: -0.73, -0.23]. Higher residential greenness appears to be associated with lower glucose. Higher physical activity can mediate this association. Our results provide evidence that ensuring access to greenspace in residential neighborhoods may provide positive health outcomes and improve public health, and should be implemented in urban planning.