Association of greenspace and natural environment with brain volumes mediated by lifestyle and biomarkers among urban residents

Objectives: To examine the association between environmental measures (greenspace and natural environment) and brain volumes and potential mediators. Study design: Prospective study. Methods: Analysis included 34,454 UK Biobank participants (53.4% female) aged 40–73 years at baseline (2006–2010). Brain volumes were measured by MRI between 2014 and 2019. Results: Greater proximity to greenspace (1000 m buffer) at baseline was associated with larger total brain (standardized β per 10% increment: 0.013; 95% CI: 0.005–0.020), grey matter (0.013; 95% CI: 0.006–0.020), and white matter (0.011; 95% CI: 0.004–0.017) volumes after adjustment for covariates and air pollution. Corresponding estimates for natural environment (1000 m) were 0.010 (95% CI: 0.004–0.017), 0.009 (95% CI: 0.004–0.015), and 0.010 (95% CI: 0.004–0.016). Similar associations were observed for 300 m buffers. Smoking and physical activity mediated associations between greenspace and brain volumes. Among biomarkers, vitamin D, red blood cell indices, and creatinine were important mediators. Significant mediators combined explained 18.5% (95% CI: 13.2–25.3%) of the association with total brain volume and 32.9% (95% CI: 22.3–45.7%) with grey matter. For natural environment, mediators combined explained 20.6% (95% CI: 14.7–28.1%) of the association with total brain volume. Conclusions: Higher coverage of greenspace and natural environment may benefit brain health by promoting healthier lifestyles and improving biomarkers, including vitamin D and red blood cell indices.

Xianwen Shang, Wei Wang, Le Tian, Danli Shi, Yu Huang, Xueli Zhang, Zhuoting Zhu, Xiayin Zhang, Jiahao Liu, Shulin Tang, Yijun Hu, Zongyuan Ge, Honghua Yu, Mingguang He