Table 1

Associations of k-means clusters with absolute and relative annualised FEV1 and emphysema changes

K-means clusterUnivariable modelsMultivariable models
Beta (SE)P valueBeta (SE)Beta (SE)
Absolute annualised FEV1 (mL/year) changesULE3.07 (2.21)0.23.63 (2.23)0.1
AD11.64 (1.86)<0.00018.84 (1.90)<0.0001
SE2.84 (2.17)0.24.98 (2.25)0.03
Relative annualised FEV1 changes (percent changes from baseline)ULE−0.27 (0.11)0.01−0.18 (0.11)0.1
AD0.09 (0.09)0.30.004 (0.09)1.0
SE−1.35 (0.10)<0.0001−1.24 (0.11)<0.0001
Absolute annualised emphysema (adjusted Perc15 density) changesULE−0.99 (0.11)<0.0001−0.89 (0.11)<0.0001
AD−0.69 (0.09)<0.0001−0.82 (0.09)<0.0001
SE−0.89 (0.11)<0.0001−0.77 (0.11)<0.0001
Relative annualised emphysema (adjusted Perc15 density) changes (percent changes from baseline)ULE−1.15 (0.16)<0.0001−1.01 (0.16)<0.0001
AD−0.82 (0.13)<0.0001−0.99 (0.14)<0.0001
SE−1.19 (0.16)<0.0001−1.07 (0.16)<0.0001
  • Absolute annualised changes were computed by subtracting Visit 1 values from Visit 2 values and dividing by the time in years between both visits for each subject. Relative annualised changes were calculated by dividing absolute annualised changes by Visit 1 values and multiplying by 100. Negative values indicate worsening of the disease between visits. Univariable linear regression models included only Visit 1 k-means cluster assignment. Multivariable models also included adjustments for age, sex, race, BMI and smoking pack-years. The reference group was the RSS cluster. P<0.05 are italicised.

  • AD, airway-predominant disease; BMI, body mass index; FEV1, forced expiratory volume in 1 s; Perc15, 15th percentile; RSS, relatively resistant smoker; SE, severe emphysema; ULE, upper lobe-predominant emphysema.