Clinical characteristics and use of healthcare resources by diagnosis of chronic cough
| Variables | No chronic cough | Chronic cough | p-value |
| Subjects n | 49 006 | 1985 | |
| Lung function# | |||
| FEV1/FVC % | 82.0±0.4 | 75.2±1.2 | <0.0001 |
| FEV1 % pred | 99.8±0.9 | 94.5±2.5 | 0.0155 |
| FEV1/FVC <70% | 4420 (8.1) | 488 (22.8) | 0.0010 |
| MMEF % pred | 76.0±1.0 | 62.6±2.8 | <0.0001 |
| FEF 50% pred | 88.4±1.0 | 74.4±3.4 | <0.0001 |
| FEF 75% pred | 77.2±1.3 | 62.7±2.6 | <0.0001 |
| SAD¶ | 15 991 (28.3) | 988 (48.0) | 0.0017 |
| Positive bronchodilator reversibility+ | 3059 (6.1) | 222 (13.0) | 0.0315 |
| Short form (SF)-12 scores | |||
| PCS scores | 52.6±0.2 | 48.7±0.6 | <0.0001 |
| MCS scores | 54.1±0.3 | 53.1±0.6 | 0.0656 |
| Comorbidities | |||
| Hypertension | 3846 (6.4) | 309 (13.1) | 0.0116 |
| Coronary heart disease | 698 (1.9) | 87 (3.2) | 0.3501 |
| Diabetes | 1203 (2.6) | 96 (3.9) | 0.2589 |
| Acute exacerbation of respiratory symptoms in the last 12 months | |||
| Emergency | 174 (0.5) | 89 (3.5) | 0.0042 |
| Hospital admission | 167 (0.4) | 119 (5.5) | 0.0002 |
Values are weighted and shown as n (%) or mean±se. All the calculations of p-value are weighted, taking into account the multistage cluster sampling design and based on χ2 test for categorical variables or t-test for continuous variables. FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; MMEF: maximal mid-expiratory flow; FEF50%: forced expiratory flow at 50% of the FVC; FEF 75%: forced expiratory flow at 75% of the FVC; SAD: small airway dysfunction; PCS: physical component summary; MCS: mental component summary. #: the parameters were measured at 20 min after inhalation of 400 µg of salbutamol; ¶: SAD was diagnosed on the basis of at least two of the following three indicators of lung function being <65% of predicted – maximal mid-expiratory flow, forced expiratory flow (FEF) 50% and FEF 75% after bronchodilator inhalation. +: a positive bronchodilator reversibility test was defined as an increase in post-bronchodilator forced expiratory volume in 1 s of >12% and >200 mL from baseline, 20 min after inhalation of 400 µg of salbutamol.