Table 1:

Baseline characteristics of 5594 patients included in the final model

Characteristic	Mean ± SD*
Follow-up time, yr	9.2 ± 2.9
Baseline age, yr	48.4 ± 6.8
Baseline FEV1, L†	2.75 ± 0.63
FEV1, % of the predicted value	78.47 ± 9.06
Weight, kg	75.9 ± 15.1
Height, m	1.72 ± 0.09
Methacholine responsiveness (O’Connor slope)‡	−12.73 (23.4)
Pack-years of smoking	40 ± 19
Sex, no. (%)
Male	3524 (63.0)
Female	2070 (37.0)
Smoking status by year 5, no. (%)
Sustained quitters	951 (17.0)
Intermittent quitters	1566 (28.0)
Continuous smokers	3077 (55.0)

Note: FEV₁ = forced expiratory volume in 1 second, SD = standard deviation.

^*Unless stated otherwise.

^†After bronchodilator treatment.

^‡Unit is change in FEV₁ per mg/mL change in methacholine concentration.