Conclusions
Our findings provide new evidence that early-life exposure to green
spaces, measured as NDVI, during the spring increases the risk of
developing allergic rhinitis in childhood. In contrast, during the
summer, similar exposure reduces the risk of allergic rhinitis. The
important bi-directional role of the season in the effects of exposure
to green spaces on allergic rhinitis is likely to be explained by
qualitative and quantitative changes in vegetation over the seasons.
This may also explain the previous inconsistent results on the
association between the exposure to green spaces and the risk of
allergic rhinitis. Our finding of effect modification of the relation
between green spaces and allergic rhinitis by air pollution levels
suggests that provision of green spaces in urban areas can be considered
as a complementary preventive measure against adverse effects of air
pollution.
Table 1 Characteristics of the baseline study population (n = 2568), The
Espoo Cohort Study 1983-2011