Table 1.
Baseline demographics of the included participants
| Variable | Total n=1458 |
Normal FEF25-75/AL− n=316 |
Low FEF25-75/AL− n=335 |
Low FEF25-75/AL+ n=806 |
| Age (years) | 64 (56.75–72) | 63 (54.75–72) | 63 (54.75–72) | 65 (58–73)*† |
| Sex (male: female) n | 744: 714 | 168: 148 | 150: 184 | 425: 382 |
| Race (n, %) | ||||
| Caucasian | 1382 (94.8) | 286 (90.5)†‡ | 321 (96.1) | 774 (94.8) |
| Black | 22 (1.5) | 9 (2.8)† | 1 (0.3) | 12 (1.5) |
| Asian | 49 (3.4) | 19 (6.0)‡ | 11 (3.3) | 19 (2.3) |
| Others | 5 (0.3) | 2 (0.6) | 1 (0.3) | 2 (0.2) |
| Smoking status (n, %) | ||||
| Current smokers | 842 (57.8) | 163 (51.6)‡ | 197 (59) | 482 (59.7) |
| Ex-smokers | 616 (42.2) | 153 (48.4)‡ | 137 (41) | 325 (40.3) |
| Smoking exposure (n, %) | ||||
| Light | 216 (14.8) | 73 (23.1)†‡ | 43 (12.8) | 100 (12.4) |
| Moderate | 568 (39) | 138 (43.7) | 133 (39.7) | 297 (36.8) |
| Heavy | 673 (46.2) | 105 (33.2)†‡ | 159 (47.5) | 409 (50.7) |
| Pack-year | 40 (25–55) | 31 (20–45)†‡ | 40 (26–55) | 41 (28–59) |
| Years quit§ | 10 (3–20) | 11 (4–24.50)‡ | 10 (4–20) | 8 (3–15) |
| BMI (kg/m2) | 27.32 (23.09–31.95) | 30.20 (25.34–34.71) | 28.94 (25.33–34.07) | 25.67 (21.88–29.82)*† |
Data are presented as median and IQR, unless otherwise stated.
In the group comparisons, the significance level for adjusted p value was set at 0.05.
*Significantly different from low FEF25-75/AL−.
†Significantly different from low FEF25-75/AL+.
‡Significantly different from normal FEF25-75/AL−.
§Only assessed in ex-smokers.
AL, airflow limitation; BMI, body mass index; FEF25-75, forced expiratory flow between 25% and 75% of vital capacity; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity.