Table 3.

Hazard ratios for asthma exacerbation.

FACTORS	HAZARD RATIO	95% CI	P-VALUE
PM2.5 level	0.99	0.95, 1.03	0.8
Age	0.79	0.68, 0.93	0.004
Female	1.45	0.7, 2.96	0.3
Air purifier used	0.88	0.42, 1.85	0.75