TABLE 4

Summary of acute exacerbations of chronic obstructive pulmonary disease (COPD) after withdrawing tiotropium in early COPD^#

	Placebo	Tiotropium	Relative risk for tiotropium versus placebo (95% CI)	p-value
Subjects n	126	136
Exacerbations per patient-year^¶
Total	0.16±0.03	0.11±0.02	0.69 (0.42–1.13)	0.14
Mild	0.06±0.02	0.03±0.01	0.42 (1.14–1.26)	0.12
Moderate	0.06±0.01	0.06±0.01	0.98 (0.55–1.77)	0.96
Severe	0.04±0.01	0.02±0.01	0.65 (0.27–1.58)	0.34
Of moderate or worse severity	0.10±0.02	0.08±0.01	0.86 (0.54–1.38)	0.52

Data are presented as mean±se, unless otherwise stated. ^#: exacerbation frequency per patient-year was referred to as the number of exacerbations for a single patient per year; ^¶: the relative risks in these categories were calculated using of Poisson regression corrected for treatment exposure and overdispersion.