Results
Of 8583 Tasmanian school children enrolled in 1968 at age 7 years, 5729
were included in the 2002 proband study (figure 1), of whom 338 were
excluded because the participant did not provide a residential address
allowing ambient air pollution exposure to be estimated. Of the
remaining 5391 participants, 2238 were excluded because they did not
participate in the 2012 proband study. Of the 3153 with data from both
the 2002 and 2012 proband studies, 2369 had a valid SPT result. There
were no important differences between those followed and those lost to
follow-up, except that those lost were more likely to be smokers or
exposed to smoke, less likely to report hay fever and being from lower
socioeconomic status (Supplementary table 2).
The mean age at the 2012 follow-up was 53 years and 50.3% were males
(Table 1). At 53 years 281 participants (8.96%) of the participants had
prevalent eczema, 115 participants (3.67%) had incident current eczema
and 201 participants (6.38%) had persistent eczema (supplementary table
3). When comparing baseline and follow-up concentrations, ambient air
pollution markers decreased slightly over time (table 1).
Association between ambient air pollution and prevalent
eczema at age
53.
There was evidence that sex modified the association (P for
interaction<0.1) between NO2 and prevalent
eczema (table 2). Thus, in males, baseline exposure to
NO2 was associated with increased risk of having
prevalent eczema at follow-up (adjusted odds ratio (aOR): 1.15 [95%CI
0.98-1.36] per IQR [2.27ppb] NO2 increase), while
higher exposure in females was associated with reduced risk of prevalent
eczema (aOR: 0.83 [95%CI 0.67-1.03 per 2.27 ppb NO2increase).
Likewise, associations also differed by sex when prevalent eczema was
classified by atopy status (table 3). In males, baseline
NO2 exposure was associated with increased risk of
having both NAE (aOR 1.39 [95%CI 1.02-1.90]) and AE (aOR 1.26
[1.00-1.59]) per 2.27 ppb NO2 increase, while
baseline PM2.5 was associated with increased risk of
having AE (aOR 1.47 [1.04-2.06]) per 1.56 µg/m3PM2.5 increase. By contrast, in females, higher
NO2 exposure at baseline was associated with a reduced
risk of having AE (aOR 0.65 [95% CI 0.43-0.99]) per 2.27 ppb
NO2 increase. A similar trend was seen at follow-up,
NO2 was associated with increased risk of prevalent NAE
(aOR 1.37 [95%CI 1.03-1.83] per 2.27 ppb) in males while in females
it was a protective of NAE (aOR 0.67 [0.44-1.01]) per 2.21 ppb
increase (Table 3). When the same associations were assessed restricting
only to those who did not changed their address (non-movers), only
negligible variation of the estimated effects were shown (supplementary
table 4).
Association between ambient air pollution at baseline and
incident current
eczema.
There was weak evidence of associations, nor effect modification by sex,
between baseline ambient air pollution markers at baseline and incident
current eczema (Table 2). Similarly, when incident current eczema was
classified by atopy groups (Table 4), there was weak evidence of
association.
Association between ambient air pollution at baseline and
persistent current
eczema.
There was evidence that sex modified the association (P for
interaction<0.1) between NO2 exposure and as a
result, increased risk of persistent eczema was stronger in males than
females (Table 2). Likewise, when persistent eczema was classified by
atopy status (Table 5), there was evidence of interaction by sex (P for
interaction<0.1). As such, NO2 exposure in
males was found to increase persistent AE risk (aOR 1.25 [95% CI
0.95-1.65] per 2.27 ppb NO2 increase, while in
females, the association tended towards reduced risk of persistent AE
(aOR 0.57 [0.36-0.91] per 2.27 ppb NO2 increase).
Similarly, PM2.5 exposure in males increased the risk of
persistent AE (aOR 1.53 [1.04-2.25] per 1.56 µg/m3PM2.5 increase) and in females the risk of persistent AE
was reduced (aOR 0.71 [0.49-1.02] per 1.56 µg/m3PM2.5 increase).
Restricted definition of non-atopic
eczema
When using the same analytic approach as the SALIA cohort
study6 there were no significant associations between
ambient air pollution markers at baseline and incident NAE with
increasing the strictness (i.e. those participants without hay fever and
SPT negative) of the definition (supplementary table 5). However, a
non-significant trend between DMR at follow-up and increased risk of
prevalent NAE was seen, and this effect became stronger when the NAE
definition became stricter (supplementary table 5). Furthermore, when
the analyses were restricted to women, there was an association between
DMR at follow-up and increased risk of prevalent eczema (supplementary
table 6).
Association between ambient air pollution at baseline and
aeroallergen sensitisation at age 53
years.
At baseline, increased exposure to PM2.5 was associated
with increased odds of being sensitized to aeroallergens (aOR 1.15
[95% CI 1.03-1.30]) per 1.56 µg/m3PM2.5 increase) at age 53 (supplementary table 7).
Furthermore, there were associations between ambient air pollution
markers and specific aeroallergen sensitisations that are described in
more detail in supplementary table 8.