Table 5

Proportional hazards model for death among subjects stratified by smoking status in univariate and multivariate models

Univariate modelsMultivariate model*
Hazards ratio95% CIHazards ratio95% CI
*Models adjusted for lung function category, age, race, sex, education, smoking status, pack years of smoking, years since regularly smoked, and body mass index.
**Severe COPD = forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) <0.70 and FEV1 <50% predicted; moderate COPD=FEV1/FVC <0.70 and FEV1 ⩾50–<80% predicted; mild COPD=FEV1/FVC <0.70 and FEV1 ⩾80%; symptoms only=presence of respiratory symptoms in the absence of any lung function abnormality; restrictive lung disease=FEV1/FVC ⩾0.70 and FVC <80% predicted.
From the First National Health and Nutrition Examination Survey 1971–5 and follow up to 1992.
Current smokers
    Severe COPD**8.05.6 to to 4.4
    Moderate COPD3.93.1 to to 2.2
    Mild COPD3.12.4 to to 1.7
    Respiratory symptoms only1.30.99 to to 1.7
    Restrictive lung disease2.82.1 to to 2.1
    No lung disease1.01.0
Former smokers
    Severe COPD9.05.8 to to 5.6
    Moderate COPD3.12.1 to to 2.7
    Mild COPD1.71.1 to 2.60.980.7 to 1.5
    Respiratory symptoms only1.20.9 to to 1.6
    Restrictive lung disease2.71.9 to to 2.9
    No lung disease1.01.0
Never smokers
    Severe COPD2.41.1 to to 3.1
    Moderate COPD2.91.9 to to 2.1
    Mild COPD2.11.5 to to 1.8
    Respiratory symptoms only1.30.9 to to 1.5
    Restrictive lung disease2.62.0 to to 2.1
    No lung disease1.01.0