Table 2– Results of univariate Cox proportional hazard model#
VariablesHR (95% CI)p-value
Age1.027 (0.987–1.069)0.1915
Smoking status
 Current0.818 (0.338–1.984)0.6573
 Former0.959 (0.475–1.936)0.9069
BMI0.977 (0.891–1.071)0.6233
FVC % pred0.965 (0.948–0.982)<0.0001
DL,CO % pred0.978 (0.963–0.993)0.0041
Pa,O2 mmHg0.963 (0.938–0.989)0.0060
MMRC score2.402 (1.495–3.858)0.0003
Walk distance m0.995 (0.992–0.998)0.0020
Lowest Sp,O2 %0.944 (0.918–0.972)<0.0001
Borg score1.285 (1.091–1.514)0.0027

  • The walk distance, lowest Sp,O2, and Borg are variables of 6-min walk test. HR: hazard ratio; BMI: body mass index; FVC: forced vital capacity; % pred: % predicted; DL,CO: diffusing capacity of the lung for carbon monoxide; Pa,O2: partial pressure of oxygen; MMRC: modified Medical Reasearch Council; Sp,O2: arterial oxygen saturation measured by pulse oximetry. #: n = 93 except for DL,CO (n = 90) and Pa,O2 (n = 90). : HRs are in relation to never-smokers.