BACKGROUND: Although the different age groups had differences in sensitivity of asthma exacerbations (AEs) to the environmental factors, no comprehensive study has examined the age-stratified effects of environmental factors on AEs. OBJECTIVE: To examine the short-term effects of 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) on asthma exacerbations. METHODS: We performed an age-stratified analysis of the short-term effects of four groups of outdoor environmental factors on AEs in Seoul Metropolitan City (Korea) from 2008 and 2012. The statistical analysis employed a Poisson generalized linear regression model, with a distributed lag non-linear model for identification of lagged and non-linear effects and convergent cross mapping for identification of causal associations. RESULTS: Analysis of the total population (n=10,233,519) indicated there were 28,824 AE events requiring admission to an emergency department during the study period. Diurnal temperature range had significant effects in pediatric (infants, preschool children, and school-aged children) and elderly people (RR: 1.056-1.078 and 1.016, respectively). Tree and weed pollen, human rhinovirus, and influenza virus had significant effects in school-age children (RR: 1.014, 1.040, 1.042, and 1.038, respectively). Tree pollen and influenza virus had significant effects in adults (RR: 1.026 and 1.044, respectively). Outdoor air pollutants (PM10, NO2, O3, CO, and SO2) had significant short-term effects in all age groups (except for CO and SO2 in infants). CONCLUSION: These findings provide the need for the development of tailored strategies to prevent asthma exacerbation events in different age groups.