The purpose of this study was to investigate the associations between surrounding greenness in the urban environment and asthma among young children. Also investigated was a possible change of this association by the distance of the child's residence to a city park.
Participants of this research were 1489 children (age 4-6) residing at their current address since birth in Jaunas, Lithuania. Child data was collected by questionnaires completed by parents or guardians. This information included child's medical history, family history, personal habits, children's height and weight, and housing and environmental conditions. Responses indicated that 112 children had clinically diagnosed asthma. The remaining 1377 children without asthma served as controls for this study.
Exposure to green spaces was objectively estimated for every child's home address using the Normalized Difference Vegetation Index (NDVI). Additionally, the Urban Atlas data for Kaunas city was used to estimate the distance from every participant's home to the nearest city park. Over 80% of the children lived within a 1000 meter distance from the nearest city park, with most of the parks having 65% of the area covered with trees.
Findings indicated that children living with a higher level of surrounding greenness were at a slightly increased risk of asthma. Living close to a city park, however, did not seem to increase the risk.
The associations between asthma and surrounding greenness remained consistent even after adjusting for other individual and environmental variables. This suggests that residential greenness has an impact on the prevalence of asthma in children.
These findings are consistent with some, but not all, previous studies. While it's been suggested that the association between surrounding greenness and asthma may be due to exposure to pollen, there are also some indications that a decrease in the biodiversity of the living environment is associated with dysfunctions of the immune system and increasing allergies. As the authors note, more research is needed to better understand the impact of exposure to green spaces on allergy and asthma in children.
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