Green Space Exposure (incl. Shinrin-yoku)

Green space exposure denotes proximity to or time spent in vegetated environments — urban parks, street trees, or forests — including the Japanese practice of shinrin-yoku (forest bathing). In a 2019 systematic review and meta-analysis of nine longitudinal cohorts (>8 million adults across seven countries), each 0.1 increment in residential Normalised Difference Vegetation Index (NDVI) within a 500 m buffer was associated with a 4% lower all-cause mortality (pooled HR 0.96, 95% CI 0.94–0.97). Mechanisms include lower chronic stress and cortisol, increased physical activity, social cohesion, reduced air pollution and heat exposure, and — for forest environments — inhalation of phytoncides (volatile wood terpenes) that increase natural killer (NK) cell activity and intracellular anti-cancer proteins; the most robust replication is for persistence beyond 7 days, while up-to-30-day persistence comes from smaller Japanese follow-up cohorts. Effects are dose-dependent and strongest for cardiovascular mortality.