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Table 4 Univariate Cox proportional hazards analysis of relationships between variables and exacerbation in ex-/non-smokers (n = 39)

From: Ambulatory pulse oximetry monitoring in Japanese COPD outpatients not receiving oxygen therapy

Variable Risk ratio 95% CI p
Age (years) 1.04 0.97 – 1.10 0.26
Unadjusted Charlson Comorbidity Index 0.93 0.57 – 1.51 0.76
Age-adjusted Charlson Comorbidity Index 1.06 0.76 – 1.46 0.74
Pack/years 1.00 0.98 – 1.01 0.69
Body mass index 0.87 0.73 – 1.03 0.10
mMRC dyspnoea grade 1.19 0.73 – 1.96 0.49
CAT score 1.08 1.00 – 1.16 0.054
PaO2 0.97 0.92 – 1.03 0.35
PaCO2 0.95 0.84 – 1.08 0.45
FEV1 0.60 0.23 – 1.53 0.28
%FEV1 0.99 0.96 – 1.02 0.45
Daytime    
     Proportion of SpO2 values < 90% (%) 1.01 0.92 – 1.11 0.78
     Mean heart rate 1.02 0.97 – 1.07 0.42
Nighttime    
     Proportion of SpO2 values < 90% 0.98 0.92 – 1.03 0.41
     3%ODI 0.92 0.82 – 1.02 0.12
     Mean heart rate 1.01 0.95 – 1.07 0.71
  1. CAT, Chronic obstructive pulmonary disease assessment test; CI, Confidence interval; FEV1, Forced expiratory volume in one second; mMRC, Modified Medical Research Council; ODI, Oxygen desaturation index; PaCO2, Partial pressure of arterial carbon dioxide; PaO2, Partial pressure of arterial oxygen; SpO2, Oxygen saturation by pulse oximetry.