Proportional hazards model for death among subjects stratified by smoking status in univariate and multivariate models
| Univariate models | Multivariate model* | |||
|---|---|---|---|---|
| Hazards ratio | 95% CI | Hazards ratio | 95% 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** | 8.0 | 5.6 to 11.5 | 3.1 | 2.2 to 4.4 |
| Moderate COPD | 3.9 | 3.1 to 4.9 | 1.7 | 1.4 to 2.2 |
| Mild COPD | 3.1 | 2.4 to 4.0 | 1.3 | 1.01 to 1.7 |
| Respiratory symptoms only | 1.3 | 0.99 to 1.7 | 1.3 | 0.97 to 1.7 |
| Restrictive lung disease | 2.8 | 2.1 to 3.6 | 1.7 | 1.3 to 2.1 |
| No lung disease | 1.0 | 1.0 | ||
| Former smokers | ||||
| Severe COPD | 9.0 | 5.8 to 14.1 | 3.5 | 2.2 to 5.6 |
| Moderate COPD | 3.1 | 2.1 to 4.5 | 1.9 | 1.3 to 2.7 |
| Mild COPD | 1.7 | 1.1 to 2.6 | 0.98 | 0.7 to 1.5 |
| Respiratory symptoms only | 1.2 | 0.9 to 1.8 | 1.1 | 0.7 to 1.6 |
| Restrictive lung disease | 2.7 | 1.9 to 3.9 | 2.0 | 1.4 to 2.9 |
| No lung disease | 1.0 | 1.0 | ||
| Never smokers | ||||
| Severe COPD | 2.4 | 1.1 to 5.3 | 1.4 | 0.7 to 3.1 |
| Moderate COPD | 2.9 | 1.9 to 4.5 | 1.3 | 0.8 to 2.1 |
| Mild COPD | 2.1 | 1.5 to 3.0 | 1.3 | 0.95 to 1.8 |
| Respiratory symptoms only | 1.3 | 0.9 to 1.8 | 1.1 | 0.8 to 1.5 |
| Restrictive lung disease | 2.6 | 2.0 to 3.4 | 1.6 | 1.2 to 2.1 |
| No lung disease | 1.0 | 1.0 | ||