Work

The Role of Greenness in Heat‑Related Mortality: A Systematic Review and Meta‑Analysis

Year: 2026

Type: review

Study designs: Systematic Review, Meta-Analysis

Abstract: Background: Rising temperatures and the frequency of heat waves are challenges that have an impact on the health and mortality of populations. A high level of greenness is emerging as a strategy to mitigate the effects of extreme heat. Objective: To assess whether higher levels of greenness are associated with reduced mortality compared with lower greenness during periods of extreme heat. Methods: In this systematic review and meta‑analysis, we searched MEDLINE, SCOPUS, WEB OF SCIENCE, CINHAL, Environment Complete, and GreenFILE. Observational studies were included. Pooled risk ratios (RRs) with 95% confidence intervals (CIs) were calculated via a random‑effects model. Results: The systematic review and meta‑analysis included 11 articles. These cover data from China, France, Germany, Jordan, Switzerland, and the USA, as well as a global analysis covering 24 countries. The meta‑analysis suggested that heat waves significantly increased mortality in areas with the lowest greenness (RR = 1.33; 95% CI: 1.15–1.55; I2 = 99.4%) and in areas with the highest greenness (RR = 1.18; 95% CI: 1.03–1.36; I2 = 97.9%). The pooled ratio of RR (RoR) indicated that the association was significantly stronger in low‑greenness areas than in high‑greenness areas (RoR = 1.11; 95% CI: 1.06–1.15; I2 = 90.5%), indicating that the heat–mortality association was 11% stronger in low‑greenness areas. The pooled associations varied descriptively across subgroup analyses, although no statistically significant differences were observed between geographical regions or study settings. Conclusion: Higher temperatures were associated with increased mortality in both low‑ and high‑greenness areas; however, the heat–mortality association was 11% stronger in low‑greenness areas. These findings suggest that greater greenness may attenuate vulnerability to extreme heat, although the limited evidence base and considerable between‑study heterogeneity warrant cautious interpretation.

Source: Annals of Global Health

DOI: 10.5334/aogh.5216