Effects of ambient temperature on volume, specialty composition and triage levels of emergency department visits

Aim: To evaluate the effects of change of ambient temperature on emergency department (ED) patient visits. Methods: This prospective observational study was conducted in the ED of National Taiwan University Hospital from January 2002 to January 2007. The daily ED patient numbers of different triage levels in different service specialties were collected and correlated with the daily average temperature (T) and change in temperature (δT) compared with the previous day. A univariote analysis was performed with the Pearson correlation and a multivariate analysis with multiple linear regression analysis. Results: A total of 505 224 patient visits were included in this study. On univariate analysis, there was no significant correlation between T and the ED volume (r=0.012, p=0.608), but there was a significant correlation between δT and ED volume (r=0.109, p<0.001). On multivariate analysis, δT and holidays were identified as independent predictors of ED volume. We established the following formula in predicting the ED patient number: y = 265.A2+(0.06×T)+(2.57 × δT)+(59.77 × holiday). There was a positive association between T and the trauma patient number, while there was a negative association between T and medical and poediatric patiient numbers. On the triage level, a low T was associated with increased patient triage level, while no significant association was noted between AT and the proportion in any triage level. Conclusions: Our study demonstrated that ambient temperature had differential effects on ED patient visits of different specialties and severities.