Lee SW, Yon DK, James CC, et al. - In this age-stratified analysis, researchers investigated how asthma exacerbations (AEs) in a population of 10,233,519 individuals in Seoul Metropolitan City (Korea) was influenced in short-term by age-stratified groups (infants, preschool children, school-aged children, adults, and elderly) of outdoor environmental factors (air pollutants, weather conditions, aeroallergens, and respiratory viral epidemics). Overall 28,824 AE events requiring admission to an emergency department were documented throughout the study. In pediatric (infants, preschool children, and school-aged children) and elderly people, significant impacts of diurnal temperature range were evident. In school-age children, significant influences of tree and weed pollen, human rhinovirus, and influenza virus were observed. Adults exhibited significant effects of tree pollen and influenza virus. Significant short-term influences of outdoor air pollutants [particulate matter ≤ 10 μm in diameter, nitrogen dioxide, ozone, CO (carbon monoxide), and SO₂ (sulfur dioxide)] were seen in all age groups (except for CO and SO₂ in infants). Findings call for tailored strategies to prevent AE events in different age groups.