The Association between Short-term Exposure to Fine Particulate Matter and Outpatient Visit in Beijing, China

Background We tried to investigate the effect of PM2.5 on daily counts of outpatient visits in the Guang'anmen Hospital to determine if short-term PM2.5 exposure with extremely high concentration affects cardiopulmonary function of Beijing residents. Methods Outpatient visits and PM2.5 data from 01/11/2011 to 03/31/2013 were extracted from the Guang'anmen Hospital and the American Embassy in Beijing, respectively. Followed by using a semi-parametric generalized additive model (GAM) with time dependent covariates, we analyzed the association between PM2.5 concentrations and daily count of outpatient visits on Day 0, 1, 2, 3, 4 and 5 of PM2.5 exposure. Results Overall, 284354 subjects were collected. There were significant associations of short-term PM2.5 exposures with outpatient visits for cardiopulmonary diseases (P<0.05). Specifically, a 10 μg/m3 increase in PM2.5 was positively associated with a 0.74% of increase in angina visit on the first day and 0.50% increased visit on the second day (P<0.05). With an increase in PM2.5, the cough and respiratory visits significantly decreased by 0.17% and 0.30% on the first day, respectively (P<0.05). However, there were significant positive associations of PM2.5 with increased cough and respiratory visits (increased by 0.17% and 0.10%, respectively) on the fifth day (P<0.05). Conclusion Our association studies showed an instant effect of PM2.5 level on cardiovascular outpatient visit in the Guang'anmen Hospital in Beijing while a lag effect on respiratory outpatient visits.