BACKGROUND: Exposure to residential greenness has been linked with improved sleep duration
however, longitudinal evidence is limited, and the potential mediating effect of ambient fine particulate matter (PM METHODS: We obtained data for 19,567 participants across seven counties in a prospective cohort in Ningbo, China. Greenness was estimated using Normalized Difference Vegetation Index (NDVI) within 250-m, 500-m and 1000-m buffer zones, while yearly average PM RESULTS: Each interquartile range (IQR) increase in NDVI within 250 m, 500 m and 1000 m was associated with increases in sleep duration of 0.044 h (95% CI: 0.028,0.061), 0.045 h (95% CI: 0.028,0.062), and 0.031 h (95% CI: 0.013,0.049), respectively. Associations were attenuated after adjusting for PM CONCLUSION: Exposure to higher levels of residential greenness was associated with increased sleep duration and a slower decline in sleep over time. County-level heterogeneity in the effects of residential greenness on sleep duration was observed. PM