Table 2.

Characteristics of included studies

Authors (Year)	Study objective	Design & sample	Study methods	Relevant findings
Chen et al. (2017)	Investigate whether living in areas high in greenness may help buffer effects of difficult family relationships for children with asthma	Cross‐sectional; 150 children age 9–17 years in Chicago who were diagnosed with asthma in 2013–2014	Hierarchical multiple regression to predict asthma measures from demographic covariates, main effects of greenness and family relationships (measured as maternal hostility), and interaction between greenness and family relationships	No main effects of NDVI (250m) on asthma control [B = 0.05, 95% CI (−9, 17), p = .53] or functional limitations [B = 0.02, 95% CI (−4, 5), p = .84]. Interaction effect of greenness x parent hostility significant for asthma functional limitations [B= −0.14, 95% CI (−2, −0.05), p = .04] but not for asthma control [B = 0.03, 95% CI (−2, 3), p = .71]
Cillufo et al. (2018)	Evaluate association between urban environmental exposures to greenness, grayness, and NO2 air pollution with respiratory and allergic symptoms	Cross‐sectional; 219 schoolchildren age 8–10 in Palermo, Italy in April 2013.	Respiratory symptoms per parent and child questionnaire; NDVI; Land cover use for greyness; NO2 concentration from land use regression model	Participants lived near each other, so little variation in NDVI. No statistically significant relationships between NDVI ≤ 0.15 (1st quartile) and pulmonary symptoms (breathlessness, wheeze) [aOR = 0.98 95% CI (0.79, 1.21)].
Donovan et al. (2018)	Assess association between natural environment and asthma in children	Cohort; 49,956 children in New Zealand (1998–2016)	Used national database to assess outcomes, analyzed via three‐staged modeling approach (NDVI only, NDVI + # land cover types, NDVI + # and type of land cover)	1 SD increase lowers asthma risk for mean lifetime NDVI [OR = 0.92, 95% CI (0.89, 0.95), p < .01) and mean lifetime # land cover types [OR = 0.93, 95% CI (0.89, 0.99), p < .05); nonnative species increased asthma risk.
Eldeirawi et al. (2019)	Examine association between respiratory symptoms and residential surrounding greenness in urban children	Cross‐sectional; 1,915 children of Mexican‐American heritage in urban Chicago, IL in 2004	Multi‐level, mixed‐effect multiple regression used to determine association between greenness and parent‐reported respiratory symptoms.	NDVI at all buffers associated with lower odds lifetime asthma for those exposed to smoke [100 m: aOR 0.43 (95% CI: 0.22–0.87); 250 m: aOR 0.39 (95% CI: 0.18–0.84); aOR 0.48 (95% CI: 0.26–0.9)]; median NDVI slightly higher for nonasthmatics at all buffers but not significant.
Feng and Astell‐Burt (2017)	To investigate whether green space lowers child asthma risk by buffering effects of heavy traffic and a lack of neighborhood safety	Cross‐sectional; 4,447 children age 6–7 years old in Australia in 2006	Cross‐tabulations used to pattern asthma cases with respect to green space quantity, and perception of heavy traffic and area safety	Living near high traffic and low greenness had higher risk of asthma (OR 1.87, 95% CI: 1.37–2.55); living in high traffic and high greenness had lower risk (OR 0.32, 95% CI: 0.12–0.84).
Lambert et al. (2017)	Systematic review and meta‐analysis of residential greenness and allergic respiratory disease in children	Meta‐analysis of three studies	Threshold of 3 studies with same outcome and exposure in same buffer; random effects used; heterogeneity set at < 80%	No significant overall association (pooled OR 1.01, CI: 0.93–1.09; I2 68%, p = .02)
Tischer et al. (2017)	Assess effect of three indices of urban built environment on allergic and respiratory conditions	Cohort; 2,472 children age 4 years from two distinct regions of Spain: Euro‐Siberian and Mediterranean	Longitudinal assessments at 1 year of age to assess asthma and bronchitis and 4 years of age to assess asthma, bronchitis, and allergic rhinitis	No significant relationships between greenness, proximity to green space, or greyness with any health outcome; Prevalence of asthma higher in Euro‐Siberian (rural) region (5%) than Mediterranean (urban; 2%); adjusted OR for asthma higher in 3rd tertile NDVI versus. 1st for cohort (aOR 1.82; CI: 0.71–4.67), Euro‐Siberian region (aOR 2.26; CI: 0.91–5.67), and Mediterranean region (aOR 2.05; CI: 0.69–6.06); proximity to green space protective for asthma but not significantly

Abbreviations: NDVI, Normalized Difference Vegetation Index; NO2, Nitrogen dioxide.