Higher temperatures are associated with increased asthma-related emergency department visits among children: a time series analysis of environmental exposures in Montreal, Canada

Asthma exacerbations are a leading cause of emergency department (ED) visits in children. Outdoor exposures such as air pollutants and meteorological factors have been associated with risk of asthma exacerbations. We evaluated the association between ambient temperature, relative humidity, and air quality on pediatric asthma-related ED visits in Montreal, Canada. In this retrospective study, we included children <= 17 years presenting with asthma to two pediatric EDs between January 1, 2017 and December 31st, 2020. Temperature and relative humidity data were obtained daily for Montreal through Weather Source (TM) and the Air Quality Health Index (AQHI) through Environment Canada. We evaluated the association between environmental exposures and the incidence of asthma-related ED visits using a quasi-Poisson regression analysis, adjusting for seasonality. We examined 21 201 asthma-related ED visits. Increased temperature was associated with an increased number of asthma-related ED visits. Compared to the reference decile (2.8 to 7.5 degrees C), the strongest association with incident ED visits was for a temperature of 15.8 to 19.3 degrees C, associated with a 37% increase in the number of asthma-related ED visits (IRR = 1.37, 95% CI 1.22, 1.54). Current day relative humidity, AQHI, and changes of the exposure levels over the previous 1 to 7 days did not have an effect on asthma-related ED visits. Adjusting for seasonality, higher temperatures were associated with an increased number of asthma-related ED visits among children while humidity and air quality were not. At a population level, this can inform hospitals of upcoming trends in ED visits.