Short-term outdoor temperature change and emergency department visits for asthma among children: a case-crossover study.

Although weather changes are known to cause asthma symptoms, their impact on asthma-related health-care utilization is poorly understood. The objective of the present study was to determine the association between short-term outdoor temperature change and asthma-related emergency department (ED) visits among children 3-18 years of age in Detroit, Michigan, in 2000-2001. Descriptive analyses of patient and ED visit characteristics were performed. A case-crossover study utilizing time-stratified controls was conducted to determine the impact of maximum temperature change and change rate measured during 4-, 8-, 12-, and 24-hour periods. Multivariable conditional logistic regression demonstrated the relation between ED visits and temperature change after controlling for other weather and pollutant measures. There were 4,804 asthma-related ED visits during the study period, and they occurred most frequently in the fall and during morning hours. The case-crossover study showed a statistically significant inverse relation between ED visits and maximum 24-hour temperature change after adjustment for climatic factors (for temperature change, odds ratio = 0.992, P = 0.04; for temperature change rate, odds ratio 0.972, P = 0.01). The association persisted after air pollutant measures were added to the model, although the association was not significant. Despite the finding that a greater 24-hour temperature change decreased the risk of asthma-related ED visits, the overall results suggested a negligible association with short-term temperature change.