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The health benefits of the great outdoors: A systematic review and meta-analysis of greenspace exposure and health outcomes

Systematic review and meta-analysis (103 observational and 40 interventional studies) reporting pooled associations of greater greenspace exposure with lower all-cause and cardiovascular mortality, lower diastolic BP and heart rate, higher HF-domain HRV, lower type 2 diabetes incidence, and lower salivary cortisol—authors stress heterogeneity and study-quality limits.

Scope

Greenspace includes parks, woodland, gardens, and residential greenness metrics—not only Japanese shinrin-yoku trials—so this paper is a wide umbrella next to forest-specific field experiments linked on Forest bathing.

Pooled quantitative highlights (meta-analytic subsets; read primary tables)

  • All-cause mortality: RR 0.69 (95% CI 0.55–0.87)
  • Cardiovascular mortality: RR 0.84 (95% CI 0.76–0.93)
  • Type 2 diabetes incidence: RR 0.72 (95% CI 0.61–0.85)
  • Diastolic BP: MD −1.97 mmHg (95% CI −3.45 to −0.19)
  • Heart rate: MD −2.57 bpm (95% CI −4.30 to −0.83)
  • Salivary cortisol: pooled estimate −0.05 (95% CI −0.07 to −0.04) on the paper’s analysed scale
  • HF HRV: pooled increase 91.87 (95% CI 50.92–132.82) on the frequency-domain metric used in constituent studies

Interpretation hygiene

  • Confounding: observational studies dominate; physical activity, socioeconomic status, and air pollution pathways are intertwined with where people live and recreate.
  • Heterogeneity: authors flag low quality and high I² for several pooled outcomes—treat headline numbers as literature summaries, not guaranteed individual effects.
  • Prescribing analogy: conclusions support maintaining accessible greenspace and nature prescriptions as population-health tools, not replacing chronic-disease treatment.

Outcomes

  • All-Cause Mortality Risk
    Higher greenspace vs lower: RR 0.69 (95% CI 0.55–0.87) for all-cause mortality in pooled eligible studies (heterogeneity/quality limits per authors).
  • Cardiovascular Mortality Rate
    Higher greenspace vs lower: RR 0.84 (95% CI 0.76–0.93) for cardiovascular mortality in pooled eligible studies.
  • Diastolic Blood Pressure
    -1.97
    mmHg (Millimetres of Mercury)
  • Heart Rate
    -2.57
    bpm (Beats Per Minute)
  • other
    Type 2 diabetes incidence RR 0.72 (95% CI 0.61–0.85); salivary cortisol pooled −0.05 (95% CI −0.07 to −0.04) on analysed scale—see full text for units and forest plots.
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