Table 3 Correlation between risk factors and the probability of hospitalizations ≧ 1/year in each group by multivariate regression analysis

HR (95%CI), P value

HR (95%CI), P value

HR (95%CI), P value

HR (95%CI), P value

FEV₁-per decrease of 10%

2.565(1.225–3.764) 0.003

2.439(1.219–3.664) 0.002

2.108(1.321–4.214) 0.005

1.884(0.871–3.265) 0.003

AE history-per increase of 1 time

3.338(1.532–4.698) <0.001

3.157(1.339–5.310)< 0.001

2.541(1.210–4.311)0.001

2.226(1.722–3.827)0.001

GOLD-per progression of 1 stage

2.765(1.555–3.827)0.008

2.672(1.246–3.981)0.005

2.519(1.433–3.646)0.001

1.987(0.592–3.218)0.037

Group-per progression of 1 level

3.102(1.426–3.223) <0.001

2.453(1.002–3.528)0.002

2.313(1.038–3.297)0.004

2.124(0.762–3.281)0.014

PaO₂-per decrease of 10 mmHg

2.384(1.542–3.456)0.02

2.176(1.256–3.642)0.006

2.987(1.777–3.562)0.007

1.733(0.888–3.213)0.028

Peak VO₂-per decrease of 10 ml/min/kg

2.182(1.214–3.628)0.003

2.815(1.118–3.823)0.033

2.143(1.143–3.427)0.004

2.054(1.076–3.665)0.029

6MWD-per decrease of 100 m

1.676(0.662–3.186)0.036

1.501(0.855–3.222)0.044

1.453(0.337–3.212)0.038

1.222(0.443–3.251)0.057

Hemoglobin -per decrease of 1 g/dL^− 1

3.121(2.325–5.981) <0.001

1(reference)

2.756(1.985–3.784) <0.001

1(reference)

Carboxyhemoglobin-per increase of 0.1 g/dL⁻¹

2.838(1.698–5.210)0.001

2.663(1.520–3.228)0.001

2.437(1.265–3.884)0.001

1.688(1.104–3.651)0.002