Growing together: how urban green spaces enhance social participation and alleviate loneliness in older adults

Abstract Urban greenness has been recognized as a potential correlator of loneliness, yet evidence from rapidly urbanizing and aging contexts remains limited. Using a longitudinal panel design based on three waves (2011, 2013, and 2015) of the China Health and Retirement Longitudinal Study (CHARLS), this study examined the association between city-level greenness cover ratio and loneliness among Chinese older adults (aged ≥ 60 years, N = 11,718). We assessed social activity participation as a mediator and PM₂.₅ as a moderator. In unadjusted random-effects models, one standard-deviation increase in green cover ratio was associated with a 0.052-unit decrease in loneliness (β = −0.052; 95% CI: (−0.073, −0.031); P < 0.001). After adjustment for sociodemographic, health, and city-level covariates, the inverse association remained statistically significant (β ranges from −0.023 to −0.020; all P < 0.05). Mediation analyses suggested that social activity participation contributed only a very small indirect component to the greenness–loneliness association (approximately 2% under lower PM 2.5 conditions), while the indirect pathway becoming weaker and imprecise at higher pollution levels. In subgroup analyses, inverse associations between green cover ratio and loneliness were more consistently observed in some age and health subgroups. These findings provide modest associative evidence that urban vegetation, air quality, and social activity participation are linked with loneliness among older adults.