Ambient Air Pollution and Asthma-Coded Hospital Admission Rates in Children Aged 0-3 Years in Spain: A Municipality-Year Urban-Rural Ecological Study.

Background/

Objectives

Asthma-coded hospital admissions in very young children represent a clinically relevant but diagnostically complex marker of severe wheezing/asthma-like morbidity.

Methods

We conducted a nationwide ecological municipality-year study of children aged 0-3 years in Spain during 2020-2022 using hospital discharge records from the Spanish Minimum Basic Data Set (MBDS/RAE-CMBD). Exposure and outcome were analyzed at the municipality-year level: the exposure metric was the contemporaneous annual mean municipality-level concentration of PM2.5, PM10, NO2, SO2, O3, and CO, and the outcome was the annual number of asthma-coded admissions, with the population aged 0-3 years as offset.

Results

The regression panel comprised 20,746 municipality-year observations, 7251 municipalities, and 3231 admissions; 93.7% of municipality-years had zero admissions. In unipollutant Poisson models adjusted for calendar year, rural-urban status, temperature, and relative humidity, incidence rate ratios per interquartile-range increase were 1.54 (95% CI 1.28-1.85) for PM2.5 and 1.89 (95% CI 1.59-2.26) for PM10. Negative-binomial and province-fixed-effect sensitivity models attenuated but did not remove the particulate-matter signal. The multipollutant model was unstable because of strong collinearity between particulate fractions and was interpreted only as an exploratory sensitivity analysis.

Conclusions

These findings should be interpreted as ecological, population-level associations between annual ambient particulate pollution and pediatric respiratory hospital burden, not as individual-level causal risk estimates.