Table 2.

Frequency and causes for exacerbation in patients with COPD

	Infrequent exacerbator	Frequent exacerbator
n	61	27
Annual exacerbation rate	1	2.6 ± 0.3
Total events of exacerbation	65	111
Causes of exacerbations
Bacterial infection	47 (72.3%)	91 (82%)
Viral infection	3 (4.6%)	4 (3.6%)
Others include unknown	15(23.1%)	16 (14.4%)

Data are presented as mean ± standard deviation