Residential greenness, respiratory symptoms and lung function in children, adolescents and adults with asthma: a cross-sectional study.

Abstract

Background: We hypothesize that green areas within cities affect the respiratory symptoms of individuals with asthma, but this effect may not be the same for all age groups.

Objective: Evaluate whether there is an association between the percentage of green area close to the residence and asthma outcomes, stratified by age group.

Methods: We included individuals with asthma from all 42 public health facilities in a Brazilian municipality with 400,000 inhabitants. Two independent researchers, blinded to clinical information regarding asthma, measured the extent of green area around the residence of study volunteers using satellite images. The primary outcome was the severity of respiratory symptoms. The secondary outcome was the presence of airway obstruction in the spirometry test carried out at the study visit. Adjusted regression analyzes evaluated whether the percentage of green area close to the residence was associated with asthma outcomes.

Results: In children-adolescents (n = 322), greater density of green area was associated with a greater frequency of uncontrolled asthma symptoms [OR 1.25, 95CI (1.02-1.54)]. In adults (n = 966), more greenness was associated with a lower frequency of uncontrolled asthma symptoms [OR 0.90, 95CI (0.81-0.99)] and a lower frequency of airway obstruction [OR 0.86, 95CI (0.78-0.96)].

Conclusions: The extent of green areas close to the residence is associated with asthma morbidity, but the direction of this association differs between child-adolescents and adults. Studies need to clarify why the effect of vegetation cover on asthma symptoms differs between children-adolescents and adults.