Air pollution and lung function in asthmatic and non-asthmatic children: A cross-sectional study with a nested case-control analysis in Ho Chi Minh City.

OBJECTIVES

This study investigated the association of air pollution and spirometry indicators, and fractional exhaled nitric oxide in stable asthmatic and non-asthmatic children.

METHODS

A cross-sectional study with a nested case-control analysis was conducted in Ho Chi Minh City (1 December 2022 to 31 January 2023), involving 36 asthmatic children conveniently recruited from a pulmonary clinic and 170 non-asthmatic students randomly selected from two districts, all aged 12-14. After propensity score matching on key covariates, the final sample included 36 asthmatic and 81 non-asthmatic participants. Data on spirometry, fractional exhaled nitric oxide, and air pollution exposures, including fine particulate matter levels, were collected via surveys and direct measurements.

RESULTS

Multivariate regression found significant associations between air pollution exposures and spirometry indicators; specific exposures linked to larger lung-function declines and fractional exhaled nitric oxide increases in asthmatic versus non-asthmatic children. In asthmatics, mosquito-coil use (≥1/week) was associated with a 5.46% FEV1/FVC drop (p = 0.043; p(diff) = 0.020); a 16.69% FEF25-75 decline (p = 0.029; p(diff) = 0.010); and an 18.30 ppb fractional exhaled nitric oxide rise (p = 0.038; p(diff) = 0.016)-none significant in non-asthmatics. In non-asthmatic children, each 1 μg/m3 PM2.5 increase was tied to a 0.113% FEV1/FVC fall (p = 0.043; p(diff) = 0.037) and window opening to a 5.18% FEF25-75 drop (p = 0.045; p(diff) = 0.041), effects absent in asthmatics.

CONCLUSIONS

Air pollution was associated with reduced lung function and elevated airway inflammation in children, with certain exposures having stronger effects in those with asthma. These findings underscore the urgency to reduce both indoor and outdoor air pollution to protect children's respiratory health.