Early-life residential greenness and sleep disturbances in preschoolers across 551 cities of China

The nexus between early-life residential greenness and sleep health in children remains underexplored. This research investigated associations of early-life greenness exposure with sleep outcomes among 101,879 preschoolers from 551 Chinese cities. Sleep status was evaluated using the Children's Sleep Habits Questionnaire (CSHQ). Greenness was estimated using satellite-derived Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) surrounding participants' home during pregnancy and post-birth period. Linear mixed-effect and random-effects logistic regression models were used to assess associations of greenness with CSHQ scores and sleep disturbance, respectively. Mediation effects of air pollution and residential distance to major roads were examined. Both prenatal and postnatal greenness exposures were significantly associated with better sleep outcomes. Specifically, an interquartile range increment in NDVI within the 250-m buffer during the entire pregnancy and from birth to investigation was associated with reductions in the total CSHQ score by 0.21 (95% confidence interval [CI]: 0.14, 0.28) and 0.22 (95% CI: 0.15, 0.29), respectively. Corresponding odds ratios for sleep disturbance were 0.96 (95% CI: 0.94, 0.98) for both periods. These associations remained consistent when considering larger buffers (500-m and 1000-m), and employing other greenness metrics like EVI and growing-season NDVI. The association between postnatal greenness exposure and sleep disturbance was partially mediated by PM_2.5, residential distance to major roads, NO₂, and SO₂. Children living in Northern China, breastfed for <6 months, or with more educated mothers showed greater benefits from greenness. Increased early-life greenness exposure appears to positively influence childhood sleep health.