Subjects’ characteristics
| Characteristics | Subjects with preserved spirometry (n=256) | Subgroup that performed exercise (n=179) |
| Age (years) | 56.1±11.0 | 54.7±11.3 |
| Female sex, n (%) | 232 (90.6) | 163 (91.1) |
| BMI (kg/m2) | 23.5±2.9 | 23.5±3.0 |
| FEV1 (% predicted) | 103±12 | 103±12 |
| FVC (% predicted) | 106±12 | 106±12 |
| FEV1/FVC (%) | 77±4 | 77±4 |
| FEV1/FVC (% predicted) | 98±5 | 98±4 |
| FEF25–75 (% predicted) | 92±23 | 91±21 |
| FEF75 (% predicted) | 41±16 | 43±17 |
| TLC (% predicted) | 101±10 | 101±10 |
| RV (% predicted) | 93±15 | 92±16 |
| (RV/TLC) (%) | 34±6 | 34±6 |
| (RV/TLC) (% predicted) | 92±12 | 92±12 |
| FRC (% predicted) | 96±18 | 97±18 |
| DcoSB adjusted for Hgb (% predicted) | 79±10 | 79±10 |
| mMRC Dyspnea Scale ≥1, n (%) | 23 (9.0) | 15 (8.4) |
| Symptoms | ||
| Subjects ever experiencing shortness of breath, n (%) | 36 (14.1) | 23 (12.8) |
| Subjects with cough ≥2 episodes/year, n (%) | 114 (44.5) | 73 (40.8) |
| Subjects with less activity than peers, n (%) | 10 (3.9) | 5 (2.8) |
| Subjects with any respiratory symptoms, n (%) | 129 (50.4) | 83 (46.4) |
| SHS exposure | ||
| Ever cabin SHS exposure, n (%) | 161 (62.9) | 102 (57.0) |
| Cabin SHS exposure (years) | 12.1±11.7 | 10.1±10.7 |
| Any form of non-cabin SHS exposure, n/N (%) | 196/210 (93.3) | 130/139 (93.5) |
| Childhood home SHS exposure, n/N (%) | 133/207 (64.3) | 87/138 (63.0) |
| Adult home SHS exposure, n/N (%) | 80/207 (38.6) | 48/138 (34.8) |
| Non-airline occupational SHS exposure, n/N (%) | 73/198 (36.9) | 53/136 (38.9) |
| Other SHS exposure, n/N (%) | 133/193 (68.9) | 90/130 (69.2) |
Demographics, lung function and secondhand smoke (SHS) exposure status in subjects with preserved spirometry and the subgroup that underwent exercise testing. Other SHS exposure was defined as non-aircraft cabin SHS exposure outside the work or home environment such as in recreational public places. Data are presented as mean±SD or number of subjects with positive value for the variable (n) out of the total number of subjects (N) and percentage of subjects (%).
BMI, body mass index; DcoSB, single-breath diffusing capacity of carbon monoxide; FEF25–75, maximum airflow at mid-lung volume; FEF75, maximum airflow at low-lung volume; FEV1, forced expiratory volume in 1 s; FRC, functional residual capacity; FVC, forced vital capacity; Hgb, haemoglobin; mMRC, modified Medical Research Council; RV, residual volume; TLC, total lung capacity.