Table 2

Respiratory impairment and prospective risk of disability in COPD

Respiratory impairment measureProspective disability measure*
PrimarySecondary
Increase in proportion of activities unable to perform (n=1051)Development of ≥1 activity unable to perform in those with no baseline disability (n=777)
Forced expiratory volume in 1 s
 Base model†

  • 1.95 (1.41 to 2.70)

  • p<0.0001

  • 1.95 (1.28 to 2.98)

  • p=0.002

 Base model + covariates†

  • 1.75 (1.26 to 2.44)

  • p=0.0009

  • 1.81 (1.17 to 2.80)

  • p=0.007

Baseline oxygen saturation
 Base model

  • 1.70 (1.23 to 2.34)

  • p=0.0012

  • 1.45 (1.00 to 2.12)

  • p=0.053

 Base model + covariates

  • 1.57 (1.13 to 2.18)

  • p=0.008

  • 1.33 (0.90 to 2.0)

  • p=0.16

  • ↵* Incident disability was based on two measures. Primary disability outcome = an increase in the proportion of activities that subject is unable to perform from wave 1 to wave 2. A significant increase was defined as that exceeding 1 SE of measurement (see Methods). Secondary outcome was development of at least one new activity that subject is unable to perform among subcohort who had no disability at baseline.

  • ↵† Results are from logistic regression analysis and are presented as ORs (95% CIs). ORs are expressed for a 1 l decrement of FEV1 and 5% decrement of oxygen saturation. Baseline model used the following predictor variables: respiratory impairment measure plus age, sex, race, and height. Covariates (potential confounders) = race, educational attainment, household income, and smoking status.