Are children's asthmatic symptoms related to ambient temperature? A panel study in Australia

Objectives: To examine the short-term effects of ambient temperature on respiratory symptoms for school children with asthma across Australia. Methods: A panel of 270 children (7-12 years) with asthma was recruited from six Australian cities. They were asked to record their respiratory symptoms every day in the morning (for night-time symptoms) and evening (for daytime symptoms) for four weeks. Daily ambient temperature, relative humidity and air pollution data were obtained from fixed monitors nearby. A mixed logistic regression model was used to examine the effects of ambient temperature on respiratory symptoms adjusted for children's sex, age, standing height, weight and air pollution. Subjects were specified as random effects. Results: The relationships between ambient temperature and respiratory symptoms were linear. Increasing temperatures induced the risks of children's asthmatic symptoms, especially for "wheeze/chest tightness" and to a lesser extent for "cough/phlegm". The effects were acute and lasted for four days (lag 0-3) in general. With increasing ambient temperature, boys were more at risk than girls. Conclusions: High ambient temperature is a risk factor for respiratory symptoms in children with asthma. As ambient temperature increases, policies and strategies for rising temperatures will be necessary to protect asthmatic children.