Results
Characteristics of the study population are presented in Table 1. Among
the 2568 participants included, 1257 (48.9%) were female. Fourteen
percent of children were exposed to maternal smoking during pregnancy,
and about 5% of mothers had been exposed to secondhand smoke during
pregnancy. The percentage of cohort members who had developed allergic
rhinitis during the follow-ups increased from 6.4% (up to six years of
age) to 26.0% (up to 27 years of age).
Distribution
of the mean values of cumulative exposure to NDVI and air pollution
levels are presented in Tables E2 (Figure S1) and E3, respectively. The
mean cumulative NDVI (SD) values within 300 m during pregnancy in spring
were significantly lower among children with allergic rhinitis up to six
years of age compared to children without allergic rhinitis [0.200
(0.158) vs. 0.244 (0.201), p =0.046]. Similarly, lower
mean cumulative NDVI (SD) values within 300 m during pregnancy in summer
were also observed among children with allergic rhinitis up to 27 years
of age compared to children without allergic rhinitis [0.794 (0.428)vs. 0.834 (0.436), p =0.037] (Table S4). Although no
statistically significant differences were found, the mean NDVI values
during pregnancy and early-life for both seasons were lower among
children with allergic rhinitis up to 12 years of age compared to
children without allergic rhinitis (Table S4).
Figure 1 shows the adjusted associations between residential exposure to
NDVI at specific time points and allergic rhinitis. There was no clear
evidence of association between the cumulative exposure to NDVI during
pregnancy and allergic rhinitis (Figure 1, Table S5). However, an
increase in cumulative exposure to NDVI during spring season in
early-life was associated with an increased risk of allergic rhinitis up
to 12 years of age [HR (95% CI) = 1.726 (1.078; 2.765)] and up to
27 years of age [HR (95% CI) = 1.703 (1.139; 2.545)]. During the
summer, an increase in the cumulative exposure to NDVI was associated
with a decrease in the risk of allergic rhinitis up to 12 years of age
[HR (95% CI) = 0.754 (0.585; 0.972)] and up to 27 years of age
[HR (95% CI) = 0.801 (0.649; 0.989)]. Similar results were observed
when considering the 500 m and 1000 m buffer sizes (Table S5).
Air pollution levels modified the
association between early-life cumulative exposure to NDVI and allergic
rhinitis. In children exposed to high levels of primary air pollutants
(PM10, PM2.5, SO2, and
NO2), an increase in NDVI during early-life in summer
decreased the risk of allergic rhinitis (Table 2). In children exposed
to low levels of primary air pollutants, an increase in NDVI values in
early-life in spring increased the risk of allergic rhinitis up to 12
and 27 years of age. Similar results were observed between early-life
cumulative exposure to NDVI during spring and summer within larger
buffer sizes (500 m and 1000 m) and allergic rhinitis among children
exposed to different levels of air pollution (Table S6). No significant
associations were observed between the cumulative exposure to NDVI
during pregnancy in both seasons and allergic rhinitis in children
exposed to different levels of air pollution (Table 2). Additionally,
the mediation analysis revealed that associations between NDVI and
allergic rhinitis do not appear to be mediated by ambient air pollution
(Table S7).