Table 1.
Study population
| Disease | No | Age (years) | Smoking status | Pack years | FEV1/VC (%) | FEV1 (% predicted) |
|---|---|---|---|---|---|---|
| Non-susceptible | ||||||
| Healthy (A) | 30 | 18–40 | Party smoking | 0–10 | >70 | >85 |
| Healthy (B) | 30 | 40–75 | Ex or current | >20 | >70 | >85 |
| Susceptible | ||||||
| Healthy (C) | 30 | 18–40 | Party smoking | 0–10 | >70 | >85 |
| COPD | ||||||
| Stage I (D1) | 30 | 40–75 | Ex or current | >10 | ≤70 | >80 |
| Stage II (D2) | 30 | 40–75 | >10 | ≤70 | 50–80 | |
| Stage III (D3) | 30 | 40–75 | >10 | ≤70 | 30–50 | |
| Stage IV (D4)* | 20 | 40–75 | >10 | ≤70 | <30 | |
| <53 | <30% | |||||
Susceptibility in young individuals is based on family history. Not susceptible means that none of the smoking family members who are at least 40 years of age have COPD. Susceptible means that the prevalence of COPD in smoking family members older than 40 years is high: 2 of 2, 2 of 3 or 3 of 3, 3 of 4 or 4 of 4. Party smoking was defined by irregularly smoking and/or able to quit smoking for at least 2 days. α-1-antitrypsin deficiency is excluded.
*Patients with a FEV1 30–50% predicted in combination with chronic respiratory failure also have stage IV.
COPD, chronic obstructive pulmonary disease.