Varying effects of greenness in the spring and summer on the development
of allergic rhinitis up to 27 years of age: The Espoo Cohort Study
Abstract
Background: Previous inconsistent evidence on effects of green
space on the development of allergic rhinitis could be explained by the
season of exposure. We explored whether the season and timing of
exposure to green space play a role in the development of allergic
rhinitis during the first 27 years of life. Methods: In a
longitudinal study of 2568 participants from the Espoo Cohort Study,
green space was assessed using the mean Normalized Difference Vegetation
Index (NDVI) within 300 m of the participant’s residence during
pregnancy and the first two years after birth during spring and summer
seasons. We applied Cox proportional hazards regression to estimate
adjusted hazard ratios (aHRs) and 95% confidence intervals (95% CI)
for the associations between cumulative exposure to NDVI (1-unit
increase) and allergic rhinitis. Results: Early-life exposure
to abundant vegetation during the spring was associated with an
increased risk of allergic rhinitis at 12 years of age [aHR (95% CI)
= 1.726 (1.078; 2.765)] and 27 years of age [1.703 (1.139;
2.545)]. However, abundant vegetation during the summer was associated
with a decreased risk of allergic rhinitis at 12 years of age [0.754
(0.585; 0.972)] and 27 years of age [0.801 (0.649; 0.989)].
Perinatal exposure to green spaces had no effect on allergic rhinitis.
Conclusions: Green space has opposite effects on the
development of allergic rhinitis in the spring and summer: early-life
exposure to green spaces during the spring increases the risk of
developing allergic rhinitis, whereas exposure to greenness in the
summer decreases this risk.