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 mu g/m(3) 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.