Jiaci

Marques-Mejías MA, et al.

J Investig Allergol Clin Immunol 2019; Vol. 29(5): 365-370

doi: 10.18176/jiaci.0364

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 [31].

Ozone is responsible for an almost 10% increase in the risk of

ED visits, especially in children aged 6-19 years [17].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 [17]. 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 (

Cupressus

arizonica, Olea europaea

) or molds (

Alternaria alternata

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

, PM

) and

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.

Acknowledgments

The authors are grateful to José Delgado PhD for his support

and work in the statistical analysis of the sample.

Funding

The authors declare that no funding was received for the

present study.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

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