Baseline characteristics of study participants stratified according to severity of FEV1 impairment
| Severity of impairment | ||||||
|---|---|---|---|---|---|---|
| Quintile 1 (n=561) | Quintile 2 (n=562) | Quintile 3 (n=561) | Quintile 4 (n=562) | Quintile 5 (n=562) | p for trend | |
| Continuous variables are shown as mean (SD) and dichotomous variables are shown as number (% of column totals) unless otherwise indicated. | ||||||
| *Geometric mean. | ||||||
| BMI=body mass index; FEV1=forced expiratory volume in 1 second; FVC=forced vital capacity; CRP=C reactive protein. | ||||||
| FEV1 (% predicted) | 70.8 (14.9) | 90.1 (2.6) | 98.0 (2.1) | 100.5 (2.4) | 118.5 (8.3) | 0.001 |
| FEV1 (l) | 2.15 (0.82) | 2.95 (0.70) | 3.23 (0.77) | 3.46 (0.82) | 3.53 (1.01) | 0.001 |
| FEV1/FVC (%) | 69.0 (14.3) | 78.5 (8.3) | 80.7 (7.8) | 82.3 (7.4) | 82.3 (7.0) | 0.001 |
| Age (years) | 53.1 (19.8) | 42.8 (18.0) | 40.2 (17.9) | 39.7 (17.6) | 46.3 (21.2) | 0.001 |
| BMI (kg/m2) | 22.5 (2.4) | 22.6 (2.2) | 22.6 (2.2) | 22.9 (2.2) | 22.9 (2.0) | 0.001 |
| Weight (kg) | 63.4 (10.6) | 64.2 (10.0 | 63.9 (9.9) | 64.1 (10.0) | 63.1 (9.7) | 0.685 |
| Males | 297 (52.9%) | 278 (49.5%) | 259 (46.2%) | 249 (44.3%) | 252 (44.8%) | 0.001 |
| Whites | 433 (77.2%) | 422 (75.1%) | 423 (75.4%) | 426 (75.8%) | 381 (67.8%) | 0.002 |
| Current smokers | 227 (40.4%) | 187 (33.3%) | 151 (26.9%) | 130 (23.1%) | 136 (24.2%) | 0.001 |
| Never smokers | 213 (38.0%) | 275 (48.9%) | 301 (53.7%) | 324 (57.7%) | 321 (57.2%) | 0.001 |
| Serum albumin (g/l) | 40.9 (3.4) | 41.6 (3.5) | 41.6 (3.6) | 41.9 (3.6) | 41.6 (3.5) | 0.001 |
| Serum folate (nmol/l) | 15.4 (14.2) | 14.8 (14.7) | 15.6 (15.6) | 14.1 (12.3) | 15.8 (12.8) | 0.952 |
| Total serum cholesterol (mmol/l) | 5.3 (1.1) | 5.1 (1.1) | 5.0 (1.1) | 5.0 (1.0) | 5.2 (1.1) | 0.154 |
| CRP (mg/l)* | 3.07 | 2.70 | 2.56 | 2.53 | 2.52 | 0.001 |
| Leucocytes (×103/μl) | 7.07 (2.41) | 6.64 (2.09) | 6.35 (1.96) | 6.34 (1.86) | 6.26 (1.97) | 0.001 |
| Fibrinogen (g/l) | 3.23 (0.88) | 3.08 (0.86) | 3.03 (0.92) | 2.88 (0.82) | 2.94 (0.74) | 0.001 |
| Triceps skinfold (mm) | 13.8 (6.6) | 14.7 (6.9) | 14.8 (6.6) | 14.3 (6.6) | 13.2 (6.1) | 0.068 |