%0 Journal Article
%T Seasonal modification of the association between temperature and adult emergency department visits for asthma: a case-crossover study
%A Jessie P Buckley
%A David B Richardson
%J Environmental Health
%D 2012
%I BioMed Central
%R 10.1186/1476-069x-11-55
%X We conducted a case-crossover study to determine whether the association between temperature and emergency department visits for asthma varies by season or month. Asthma emergency department visits among North Carolina adults during 2007¨C2008 were identified using a statewide surveillance system. Marginal as well as season- and month-specific associations between asthma visits and temperature were estimated with conditional logistic regression.The association between temperature and adult emergency department visits for asthma is near null when the overall association is examined [odds ratio (OR) per 5 degrees Celsius£¿=£¿1.01, 95% confidence interval (CI): 1.00, 1.02]. However, significant variation in temperature-asthma associations was observed by season (chi-square£¿=£¿18.94, 3 degrees of freedom, p <0.001) and by month of the year (chi-square£¿=£¿45.46, 11 degrees of freedom, p <0.001). ORs per 5 degrees Celsius were increased in February (OR£¿=£¿1.06, 95% CI: 1.02, 1.10), July (OR£¿=£¿1.16, 95% CI: 1.04, 1.29), and December (OR£¿=£¿1.04, 95% CI: 1.01, 1.07) and decreased in September (OR£¿=£¿0.92, 95% CI: 0.87, 0.97).Our empirical example suggests that there is significant seasonal variation in temperature-asthma associations. Epidemiological studies rarely account for interactions between ambient temperature and temporal matching factors (such as month of year) in the case-crossover design. These findings suggest that greater attention should be given to seasonal modification of associations between temperature and respiratory outcomes in case-crossover analyses of other environmental asthma triggers.Ambient temperature is a potential confounding factor in many studies of the health effects of environmental exposures, such as air pollution. Time-series and case-crossover designs have become widely used in epidemiological studies of environmental triggers of respiratory health outcomes, such as asthma. The case-crossover study design with time-stratified sampling is appeali
%K Asthma
%K Temperature
%K Season
%K Case-crossover
%U http://www.ehjournal.net/content/11/1/55