Associations of exposure to green space with problem behaviours in preschool-aged children

Background: Limited evidence is available regarding the association of green-space exposure with childhood behavioural development. This study aimed to investigate the associations of exposure to green space with multiple syndromes of behavioural development in preschool children. Methods: This cross-sectional study was conducted in Wuhan, China from April 2016 to June 2018. We recruited a sample of 6039 children aged 5-6 years from 17 kindergartens located in five urban districts of the city. We measured the greenness using average Normalized Difference Vegetation Index (NDVI) within a circular buffer area of 100 metres surrounding the central point of residences and kindergartens. We calculated the residence- kindergarten-weighted greenness by assuming that children spent 16 hours per day at home and 8 hours at kindergarten. The problem behaviours of children were evaluated at kindergarten using the Childhood Behavioral Checklist (CBCL) and standardized into problem behavioural T scores. Linear mixed-effect models and linear-regression models were used to estimate the associations. Results: We observed decreases in problem behaviours associated with kindergarten and residence-kindergarten-weighted surrounding greenness in preschool children. For example, a one-interquartile range increase in kindergarten and residence-kindergartenweighted NDVI was associated with decreased T scores for total behaviour by -0.61 [95% confidence interval (CI): -1.09, -0.13) and -0.49 (95% CI -0.85, -0.12), anxiety and depression by -0.65 (95% CI: -1.13, -0.17) and -0.46 (95% CI: -0.82, -0.10), aggressive behaviour by -0.53 (95% CI: -1.01, -0.05) and -0.38 (95% CI: -0.75, -0.02) and hyperactivity and attention deficit by -0.54 (95% CI: -1.01, -0.07) and -0.48 (95% CI: -0.83, -0.12), respectively. Stratified analyses indicated that the associations of green-space exposure with problem behaviours were stronger in boys than in girls. Conclusions: Children attending kindergartens with higher levels of surrounding green space exhibited better behavioural development. The mechanisms underlying these associations should be explored further.