at baseline and at follow-up. Compared to TTFC >60 minutes, the multivariate adjusted ORs (95% CI) for emphysema at the baseline questionnaire were 1.49 (0.95–2.36), 1.50 (0.98–2.31), and 2.19 (1.36–3.54) for TTFC 31–60 minutes, 6–30 minutes, and ≤5 minutes, respectively; at the follow-up questionnaire the multivariate adjusted ORs for emphysema for the same comparisons were 1.43 (1.05–1.94), 1.83 (1.38–2.43), and 2.50 (1.80–3.47), respectively.
