Table 2 Frequency and causes for exacerbation in patients with COPD
From: Clinical features of Japanese patients with exacerbations of chronic obstructive pulmonary disease
| Â | Infrequent exacerbator | Frequent exacerbator |
|---|---|---|
n | 61 | 27 |
Annual exacerbation rate | 1 | 2.6 ± 0.3 |
Total events of exacerbation | 65 | 111 |
Causes of exacerbations | Â | Â |
 Bacterial infection | 47 (72.3%) | 91 (82%) |
 Viral infection | 3 (4.6%) | 4 (3.6%) |
 Others include unknown | 15(23.1%) | 16 (14.4%) |