Effect of greenness on asthma in children: A systematic review
Greenness may help protect children from asthma by moderating factors contributing to this highly prevalent childhood respiratory disease
The relationship between exposure to greenness and child asthma represents one area of interest for public health. As asthma is the most prevalent child respiratory disease internationally, understanding the role of greenness in exacerbating or diminishing this condition may have important public health implications. A previous systematic review and meta‐analysis of related research published in 2017 found inconsistent results.
This current review (conducted in 2019) sought to determine if further research might show different results. After excluding the studies included in the 2017 review, only seven articles met the inclusion criteria for this updated review. “Inclusion criteria were international publications of primary research results relevant to the relationship between asthma and measured greenness in children under age 18, written in English language.” While methods for measuring greenness differed across studies, the most common measurement was the satellite-derived Normalized Density Vegetation Index (NDVI). Of the seven studies, six used NDVI for at least one measure of greenness. Of these six, four examined only one buffer distance (either 100m, 200m, 250m, or 500m). One study used nested buffers of 100m, 250m, and 500m — a suggested practice for approximating greenness near the home, neighborhood, and larger community.
Six of the seven studies reported no statistically significant direct relationships between greenness and child asthma. One study found that a higher level of greenness was associated with a lower risk of asthma. The specific finding was that a 1 standard deviation increase in NDVI was associated with a 6% lower risk of asthma. None of the studies found a negative direct association between greenness and child asthma, which means that the studies found no indication that greenness is detrimental to child asthma. Some evidence indicated that greenness is a protective factor for child asthma by way of other factors which may negatively affect child asthma, such as difficult family relationships, high traffic volume, and exposure to tobacco smoke.
“This review found either positive or no direct association between greenness and child asthma.” These results are consistent with the review conducted in 2017. This updated review also found that greenness may mediate factors contributing to child asthma. These findings add support to other research showing that greenness may be considered a community asset for promoting health.
Hartley, K., Ryan, P., Brokamp, C., Gillespie, G.L., (2020). Effect of greenness on asthma in children: A systematic review. Public Health Nursing