Table 2.

Factors Associated With Abnormal Postbronchodilator FEV₁/SVC Ratio of < 0.7 Among Smokers With Normal Spirometry Results^a (n = 854)

Variable	OR (95% CI)	P Value
Age, every 10 y	1.91 (1.51-2.45)	< .001
Pack-years, every 10 y	1.06 (0.99-1.14)	.09
Postbronchodilator FEV1 % predicted	0.96 (0.94-0.97)	< .001
% Emphysema	1.13 (1.03-1.25)	.008
Female sex	0.68 (0.45-1.04)	.08

Variables tested but not retained for the final model include: residual volume to total lung capacity ratio, race, and current smoking. Data regarding percent emphysema, residual volume to total lung capacity ratio, and current smoking were missing in 7, 9, and 9 participants, respectively. We performed an additional analysis after multiple imputations accounting for missing values showing similar findings (e-Table 1). SVC = slow vital capacity.

^aNormal spirometry results defined as postbronchodilator FEV₁ ≥ 80% and postbronchodilator FEV₁/FVC ≥ 0.7.