Socioeconomic Inequalities in Residential Greenness: A Systematic Review and Meta-Analysis.

Abstract

Residential greenness has been linked to multiple health benefits. However, its distribution across socioeconomic groups has not been systematically quantified. The aims are to: (i) characterize the magnitude of socioeconomic inequalities in the distribution of residential greenness, as measured by NDVI, across urban populations; (ii) evaluate the consistency of these inequalities across geographic regions and investigate potential sources of between-study heterogeneity; and (iii) synthesize existing evidence to identify knowledge gaps and inform equity-oriented urban and public health policies directed toward the fair distribution of health-promoting environmental resources. We systematically searched PubMed, WoS, Scopus and CINHAL from their inception to 22 July 2024 and updated the search on 24 December 2025. We included observational studies of predominantly urban populations (≥85% urban) that compared high versus low income and/or education in relation to residential greenness, as assessed using Normalized Difference Vegetation Index (NDVI). Two reviewers independently screened records, extracted data, and assessed methodological quality using the Newcastle-Ottawa Scale. The DerSimonian and Laird method were used for pooling standardized mean differences (SMDs) and odds ratios (ORs) with their 95% confidence intervals (CIs). Subgroup analyses by geographic region and NDVI buffer size were conducted. Twenty-six studies (10 cross-sectional and 16 longitudinal), including 9,411,596 participants from 14 countries, were eligible. For continuous NDVI, the highest versus lowest income groups had significantly higher NDVI (SMD=0.50; 95% CI: 0.31-0.69; seven studies), as did the highest versus lowest education groups (SMD=0.34; 95% CI: 0.13-0.56; seven studies). For categorical NDVI, higher income was associated with an increased likelihood of living in a greener neighborhood (OR=1.54; 95% CI: 1.32-1.81; 10 studies), while higher education was associated with a modest increase in likelihood (OR=1.20; 95% CI: 1.06-1.35; 15 studies). Subgroup analyses showed no significant differences by geographic region, while analyses by NDVI buffer size suggested stronger income-related differences in greenness when smaller residential buffers were used. Substantial between-study heterogeneity was observed across analyses. Residential greenness is unequally distributed across socioeconomic strata, with higher-income and better-educated urban residents consistently residing in greener neighborhoods. These findings provide evidence relevant to environmental injustice and support the development of equity-oriented urban greening policies that prioritize socioeconomically disadvantaged communities.