Despite a variety of health benefits associated with trees, previous findings on links between tree canopy and asthma have been mixed. Little is known about the association of tree canopy with asthma emergency department (ED) visits and hospitalizations at the neighborhood level. This study examines associations between tree canopy and pediatric asthma ED visit/hospitalization rates among the Connecticut population at the census tract level and investigates the moderating effect of social vulnerability on these associations. Using data of the combined pediatric asthma ED visits and hospitalizations (from 2010 to 2014), tree canopy coverage, and area-based social vulnerability, we applied multivariate negative binomial regression models, controlling for confounders including ozone and road density. Results show that every 10-percentage point increase in tree canopy cover was expected to bring a 4% decrease in asthma ED visit/hospitalization rates. Further, every 10-percentage point increase in social vulnerability index was associated with an 18% increase in asthma ED visit/hospitalization rates. We also found a nonlinear association, indicating a U-shape effect of tree canopy on pediatric asthma ED visit/hospitalization rates. The levels of social vulnerability moderated the association between the nonlinear effect of tree canopy and asthma ED visit/hospitalization rates (β = -5.629, p =.004). Findings suggests that tree canopy may help reduce pediatric asthma ED visits and hospitalizations. Particularly, the benefits of tree canopy in decreasing pediatric asthma ED visits and hospitalizations would be more effective in more socially vulnerable areas.

尽管与树木相关的各种健康益处，但之前关于树冠与哮喘之间联系的研究结果喜忧参半。关于树冠与邻里哮喘急诊 (ED) 就诊和住院的关联知之甚少。本研究检查了康涅狄格州人口普查区树冠与儿童哮喘 ED 就诊/住院率之间的关联，并调查了社会脆弱性对这些关联的调节作用。使用儿童哮喘 ED 就诊和住院（2010 年至 2014 年）、树冠覆盖率和基于区域的社会脆弱性的综合数据，我们应用多元负二项式回归模型，控制包括臭氧和道路密度在内的混杂因素。结果表明，树冠覆盖率每增加 10 个百分点，预计哮喘 ED 就诊/住院率会降低 4%。此外，社会脆弱性指数每增加 10 个百分点，哮喘就诊/住院率增加 18%。我们还发现了非线性关联，表明树冠对儿童哮喘 ED 就诊/住院率的 U 形影响。社会脆弱性水平缓和了树冠的非线性效应与哮喘 ED 就诊/住院率之间的关联 (β = -5.629, p =.004)。研究结果表明，树冠可能有助于减少儿童哮喘 ED 就诊和住院治疗。特别，