The association between greenness exposure and arthritis in middle-aged and older Chinese adults, mediated by climate factors

Arthritis is a common health issue among middle-aged and older adults, significantly impacting their quality of life. While previous studies have explored various risk factors for arthritis, the relationship between green space exposure and arthritis risk remains underexplored. This study aims to investigate the correlation between green space exposure, as measured by the Normalized Difference Vegetation Index (NDVI), and arthritis risk among middle-aged and older adults in China using a cross-sectional approach. Data for the present study were extracted from the 2015 wave of the China Health and Retirement Longitudinal Study (CHARLS), focusing specifically on middle-aged and older adults aged 45 years and above. Greenness exposure was quantified using the NDVI. Generalized linear models were used to assess the association between NDVI and arthritis. Climatic variables (relative humidity, precipitation) and metabolic equivalents were evaluated as correlates and potential mediators of this relationship. The study included a total of 7,985 participants, of whom 3,519 had arthritis and 4,466 did not. In the fully adjusted model, NDVI showed a positive correlation with arthritis. Specifically, the odds ratio (OR) of arthritis for each interquartile range (IQR) increase in NDVI was 1.14 (95% CI: 1.02–1.27). Additionally, annual precipitation, annual relative humidity, and metabolic equivalents all showed positive associations with arthritis prevalence. Further mediation analysis indicated that annual precipitation significantly mediated the relationship between NDVI and arthritis, with a proportion mediated of 5.31%. Higher NDVI was associated with a higher prevalence of arthritis, and annual precipitation partly explained this association. The findings suggest that environmental factors, including greenery and climate, may be considered in future strategies aimed at understanding and addressing joint disease burdens. The study was approved by the Institutional Review Board of Peking University (Code: IRB00001052-11015) and conducted in accordance with the Declaration of Helsinki, with written informed consent obtained from all participants. • Based on CHARLS 2015 data, a per IQR increase in NDVI was associated with a 14% higher prevalence of arthritis. • Mediation analysis indicated that annual precipitation partially accounted for the observed association between NDVI and arthritis prevalence. • Regions with higher levels of green space may consider integrating environmental factors, such as greenery and climate, into joint disease prevention and management strategies.