Demographic and clinical characteristics at the year 25 study visit and spirometry at the year 30 study visit
| Emphysema | No emphysema | |
| Subjects | 172 | 2319 |
| Age years | 50±3.5 | 50±3.6 |
| Female | 77 (45) | 1350 (58) |
| Race | ||
| Black | 115 (67) | 1031 (44) |
| White | 57 (33) | 1288 (56) |
| Clinical centre | ||
| Birmingham | 38 (22) | 550 (24) |
| Chicago | 32 (19) | 518 (22) |
| Minneapolis | 57 (33) | 569 (25) |
| Oakland | 45 (26) | 682 (29) |
| Height cm | 171±9.1 | 170±9.4 |
| BMI kg·m−2 | 27±5.5 | 30±7.1 |
| Education years | 13±2.4 | 15±2.6 |
| Pack years at year 25 | 20±15 | 4.0±8.4 |
| Cigarettes per day among current and former smokers only | 8.2±9.3 | 1.2±4.1 |
| Smoking status | ||
| Never | 26 (15) | 1542 (66) |
| Former | 36 (21) | 515 (22) |
| Current | 110 (64) | 262 (11) |
| Spirometry | ||
| FEV1 L | 2.45±0.79 | 2.74±0.75 |
| FEV1 % predicted | 82.6±20.3 | 92.8±15.5 |
| FVC L | 3.5±0.94 | 3.6±0.98 |
| FVC % predicted | 92.3±15.9 | 94.0±14.5 |
| FEV1/FVC ratio | 0.70±0.11 | 0.77±0.06 |
Data are presented as mean±sd or n (%), unless otherwise stated. BMI: body mass index; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity.