3 | Results
Table 1 shows characteristics of the 150 subjects at enrollment and the
remission rate of AD at age 3. According to the SCORAD at enrollment, AD
severity was ‘mild’ in 72 (48.0%), ‘moderate’ in 61 (41.0%), and
‘severe’ in 17 (11.0%) children. The remission rate of AD at age 3 was
36.0%. There was no significant difference in the remission rate
between boys and girls (p = .529). Sensitization rates to HDM and
pollen at age 3 were 52.7% and 35.3%, respectively.
The monthly average level of PM10 exposed to each
subject was 47.8 ± 3.9 µg/m3 for the whole study
period (Table 2). Average values of ambient NO2,
SO2, O3, CO, temperature, and RH for the
residential places of the young children were 32.1 ± 3.8 ppb, 5.4 ± 1.2
ppb, 22.8 ± 1.6 ppb, 564.5 ± 63.1 ppb, 12.9 ± 0.5°C, and 63.9 ± 5.1%,
respectively.
Table 3 shows the long-term effects of PM10 exposure on
AD persistence and inhalant allergen sensitization in young children.
The overall hazard ratio (HR) of AD persistence at age 3 was 1.06
[95% confidence interval (CI): 0.99−1.14] due to long-term exposure
to PM10 by 1 µg/m3. There was no
significant association between PM10 exposure and the
incidence of sensitization to HDM or pet allergens at age 3. However, a
1 µg/m3 increase in PM10 exposure
significantly increased pollen sensitization at age 3 (HR = 1.19; 95%
CI: 1.06 − 1.33).
Effects of PM10 on AD persistence and inhalant allergen
sensitizations stratified by severity were then evaluated, because the
disease course over time was mostly affected by its severity (Table 4).
In children with moderate or severe AD, there were significantly
positive associations between AD persistence and long-term exposure to
PM10. Furthermore, the higher the SCORAD at enrollment,
the greater the PM effect; HR of AD persistence was 1.23 (95% CI:
1.07−1.40) for the moderate group and 1.67 (95% CI: 1.16−2.41) for the
severe group by 1 µg/m3 increase of
PM10 exposure. However, AD persistence in the mild group
was not affected by long-term exposure to PM10.
When effects of ambient PM10 exposure on incidence of
HDM sensitization were stratified by severity, there were no
statistically significant effects in any subgroups, although theP -value was close to 0.05 in the severe group (HR = 1.45; 95%
CI: 0.98−2.13, p = .058). PM exposure was also not associated
with sensitization to pet allergens either, regardless of AD severity.
Of interest, the effect of ambient PM10 exposure on
pollen sensitization was significant in the moderate group (HR = 1.33;
95% CI: 1.08−1.61). In the severe group, the association of ambient
PM10 exposure with pollen sensitization could not be
evaluated statistically because the number of patients was too small.