TABLE 2

Association between chronic bronchitis (CB⁺) and forced expiratory volume in 1 s (FEV₁) decline

	Model 1		Model 2
	β (95% CI)	p-value	β (95% CI)	p-value
Subjects n	270		259
COPD CB⁺	−35.2 (−57.9–−12.5)	0.002	−38.2 (−61.7–−14.6)	0.002
Male COPD CB⁺	−42.8 (−77.3–−8.2)	0.016	−42.8 (−78.1–−7.6)	0.018
Female COPD CB⁺	−29.4 (−58.7–−0.05)	0.050	−36.1 (−67.1–−5.2)	0.022

Annual lung function decline (mL·year^-1) was calculated by dividing the difference between two FEV₁ measurements by the number of years between the two measurements. β-values represent the additional decline of FEV₁ in chronic obstructive pulmonary disease (COPD) CB⁺ subjects compared to COPD subjects without chronic bronchitis. Model 1: age and sex^# adjusted; model 2: adjusted for age, sex^# and pack-years of cigarette smoking. ^#: unstratified analyses only.