Univariate Cox proportional hazard analyses for the time to the first exacerbation of COPD
| Variable | HR | 95% CI | p-value |
| Age years | 0.98 | 0.93–1.03 | 0.4 |
| BMI, kg·m−2 | 0.89 | 0.77–1.02 | 0.096 |
| mMRC unit | 1.65 | 1.08–2.50 | 0.02 |
| CAT points | 1.09 | 1.04–1.14 | 0.0006 |
| Prior exacerbation n | 2.17 | 1.29–3.51 | 0.0048 |
| FEV1 L | 0.32 | 0.16–0.60 | 0.0002 |
| FEV1 % pred | 0.97 | 0.95–0.98 | <0.0001 |
| RV/TLC % | 1.07 | 1.02–1.11 | 0.018 |
| DLCO mL·min−1·mmHg−1 | 0.94 | 0.87–1.02 | 0.2 |
| WBC ×100·μL-1 | 0.99 | 0.97–1.01 | 0.5 |
| Neutrophils ×100·μL-1 | 0.99 | 0.96–1.01 | 0.4 |
| Eosinophils ×10·μL-1 | 0.99 | 0.95–1.03 | 0.6 |
| Eosinophils % | 0.94 | 0.72–1.20 | 0.6 |
| eGFR mL·min−1·1.73 m−2 | 1.01 | 0.99–1.04 | 0.4 |
| CRP mg·dL−1 | 0.61 | 0.13–1.55 | 0.4 |
| IgA mg·dL−1 | 0.99 | 0.99–1.00 | 0.34 |
| cFLC mg·dL−1 | 0.97 | 0.94–1.00 | 0.06 |
| cFLC low/normal versus high# | 1.44 | 0.43–9.00 | 0.59 |
| cFLC low versus normal/high# | 7.42 | 2.63–18.47 | 0.0005 |
HR: hazard ratio; CI: confidence interval; BMI: body mass index; mMRC: modified British Medical Research Council scale; CAT: COPD assessment test; FEV1: forced expiratory volume in 1 s; % pred: % predicted; RV/TLC: residual volume/total lung capacity ratio; DLCO: diffusing capacity of the lung for carbon monoxide; WBC: white blood cell; eGFR: estimated glomerular filtration rate; CRP: C-reactive protein; cFLC: combined free light chain. #: Variable was used as the nominal variable.