Residential green space and medication sales for childhood asthma: A longitudinal ecological study in Belgium

ABSTRACT Background Living in green environments has been associated with various health benefits, but the evidence for positive effects on respiratory health in children is ambiguous. Objective To investigate if residential exposure to different types of green space is associated with childhood asthma prevalence in Belgium. Methods Asthma prevalence was estimated from sales data of reimbursed medication for obstructive airway disease (OAD) prescribed to children between 2010 and 2014, aggregated at census tract level (n = 1872) by sex and age group (6–12 and 13–18 years). Generalized log-linear mixed effects models with repeated measures were used to estimate effects of relative covers of forest, grassland and garden in the census tract of the residence on OAD medication sales. Models were adjusted for air pollution (PM10), housing quality and administrative region. Results Consistent associations between OAD medication sales and relative covers of grassland and garden were observed (unadjusted parameter estimates per IQR increase of relative cover, range across four strata: grassland, β = 0.15–0.17; garden, β = 0.13–0.17). The associations remained significant after adjusting for housing quality and chronic air pollution (adjusted parameter estimates per IQR increase of relative cover, range across four strata: grassland, β = 0.10–0.14; garden, β = 0.07–0.09). There was no association between OAD medication sales and forest cover. Conclusions Based on aggregated data, we found that living in close proximity to areas with high grass cover (grasslands, but also residential gardens) may negatively impact child respiratory health. Potential allergic and non-allergic mechanisms that underlie this association include elevated exposure to grass pollen and fungi and reduced exposure to environmental biodiversity. Reducing the dominance of grass in public and private green space might be beneficial to reduce the childhood asthma burden and may simultaneously improve the ecological value of urban green space.