Marques-Mejías MA, et al.
J Investig Allergol Clin Immunol 2019; Vol. 29(5): 365-370
© 2019 Esmon Publicidad
Furthermore, it has been suggested that the effect of PM
depends mainly on particles measuring less than 2.5 µm,
because they can remain in the atmosphere for longer periods
and can access the respiratory tract easier than larger ones .
Ozone is responsible for an almost 10% increase in the risk of
ED visits, especially in children aged 6-19 years .Although
we could not find strong correlations, the groupmost susceptible
to ozone was that comprising children aged 8-15 years. This
finding is consistent with previous reports . For the total
population, we found an inverse correlation, probably because
of other factors that affect the pediatric population or because
the values were obtained using different sampling devices.
The relationship we found between air pollutants and
pediatric admissions to the ED in the scatterplots is similar to
those obtained in other cohorts in Spain [32-33].
In industrialized countries, the prevalence of sensitization
to pollen has increased in recent decades, probably owing to
the interaction between pollen grains and air pollutants mainly
in large cities [30,34]. Pollen concentrations have been linked
to increases in the frequency of ED visits. In Madrid, data
from 3 cohorts have demonstrated this association in the past
20 years [14,35,36]. Our results confirm the importance of
grass pollen allergens as relevant triggers of asthma attacks
during springtime, particularly as pollination peaks in May
(34% of allergic patients were attended in the ED owing to
exacerbations during this month). This percentage probably
underestimates the number of sensitized patients attending
the ED because of the low percentage of referrals to our unit
(22.3% in total).
Interestingly, we did not find any correlation between ED
admissions and the other pollen families analyzed (
arizonica, Olea europaea
) or molds (
Further investigations must be designed to seek alternative
explanations for these findings.
One of the main limitations when studying asthma in the
pediatric population is the lack of objective diagnostic tools,
with the result that the diagnosis is usually based on clinical
data. Because this is a retrospective study, some elements of
the ED visits may not have been recorded thoroughly, such as
classification of the episodes by severity. Moreover, follow-up
of these patients needs to be appropriate in order to clearly
assess the probable causes of multiple exacerbations.
Data regarding pollutants were extracted using 2 different
measurement sites—Plaza Castilla Station (NO
Barrio El Pilar station (ozone)—and the actual address of
the patients was not registered. Both stations covered living
areas considered for this analysis. However, since we do not
know the distance from patients’ homes and the measurement
tools used, we cannot estimate individual data for exposure
to pollutants. This might also explain the differences between
data for our sample and previously published data.
Our study was conducted in one of the largest pediatric
EDs in Madrid. Therefore, it seems reasonable to assume that
a 1-year sample of care in this type of pediatric ED can be
extrapolated to other tertiary hospitals. However, the same
results probably cannot be generalized to smaller health care
institutions, not only because of the heterogeneity of treatment
protocols, but also because of the expected variability in terms
of exposure to air pollutants. Individual data should also be
recorded regarding exposure to irritants such as smoke.
Despite the limitations of this observational retrospective
study, our results highlight the complex interaction between
the multiple factors that can affect asthma in the pediatric
population. In addition, this large-scale study stresses the need
for a multidisciplinary approach in the follow-up of pediatric
patients with asthma exacerbations.
The authors are grateful to José Delgado PhD for his support
and work in the statistical analysis of the sample.
The authors declare that no funding was received for the
Conflicts of Interest
The authors declare that they have no conflicts of interest.
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