Estimated lag day effect and lag-cumulative effect of outdoor environmental factors on COPD exacerbation
Of the three air pollutants and two external environmental factors, the only factor affecting COPD exacerbation was PM10 (Figure 2A-E). In particular, PM10 affected COPD exacerbation on lag days 4, 5, and 6 and had a hazard ratio (HR) of 1.0404 (95% CI [1.0089, 1.0729]) at lag day 5 (Table 3). PM10 also had a cumulative effect from lag day 6 to lag day 10 (Figure 2A). The remaining factors NO2, SO2, SS, and WS did not influence COPD exacerbation (Figure 2B-E).