Associations and pathways between residential greenness and hyperuricemia among adults in rural and urban China.

BACKGROUND: Residential greenness may decrease the risk for hyperuricemia in rural areas, but the urban-rural disparities in this association and underlying pathways have not been studied. OBJECTIVES: To investigate the associations and potential pathways between residential greenness and hyperuricemia in urban and rural areas. METHODS: The baseline survey of the China Multi-Ethnic Cohort (CMEC) was used. Hyperuricemia was defined as serum uric acid (SUA) > 417 µmol/L for men and >357 µmol/L for women. The satellite-based normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI) were used to capture residential greenness. A propensity score inverse-probability weighting method was used to assess urban-rural differences in the associations between residential greenness and hyperuricemia, with possible mediation effects of physical activity (PA), body mass index (BMI), PM2.5, and NO2 examined by causal mediation analyses. RESULTS: A total of 72,372 participants were included. The increases in the EVI500m and NDVI500m residential greenness were associated with a decreased risk for hyperuricemia and the SUA level in both urban and rural areas. For example, each 0.1-unit increase in EVI500m was associated with a decreased hyperuricemia risk of 7% (OR = 0.93 [0.91, 0.96]) and a decreased SUA level of -1.77 µmol/L [-2.60, -0.93], respectively; such associations were stronger in urban areas for both the risk for hyperuricemia (OR = 0.84 [0.83, 0.86]) and SUA level (-7.18 µmol/L [-7.91, -6.46]). The subgroup analysis showed that the greenness-hyperuricemia/SUA association varied by age, sex, and annual household income. The percentage of the joint mediation effect of PA, BMI, PM2.5, and NO2 on the association between EVI500m and the risk for hyperuricemia was higher in urban (34.92%) than rural areas (15.40%). BMI, PM2.5, and PA showed significantly independently mediation effects for the greenness-hyperuricemia association in both rural and urban areas. CONCLUSIONS: Exposure to residential greenness was associated with a decreased risk for hyperuricemia, partially through the pathways of PA, BMI, PM2.5, and NO2, which varied in urban and rural areas.