Table. Baseline characteristics before and after matching.
| Theophylline group | (Potential) control group | ||||
|---|---|---|---|---|---|
| After matching | Absolute STD (%) | Before matching | Absolute STD (%) | ||
| Number of patients (n) | 1496 | 1496 | – | 23354 | – |
| Sex: male (%) | 58 | 59 | 1.6 | 54 | 8.8 |
| Age (mean and SD) | 68 (10.6) | 68 (10.5) | 0.1 | 67 (11.5) | 12.0 |
| BMI (mean and SD) | 28 (5.6) | 28 (5.5) | 0.7 | 28 (5.3) | 3.8 |
| FEV1 in % of target value (mean and SD) | 65 (28.3) | 65 (25.7) | 0.3 | 74 (27.0) | 35.2 |
| Smokers (%) | 24.5 | 25.7 | 0.1 | 24.5 | 1.2 |
| Coordinating pulmonologist (%) | 11.9 | 11.6 | 0.8 | 5.8 | 21.6 |
| Emergency inpatient treatment in preceding 9 months (%) | 11.7 | 11.9 | 0.6 | 3.7 | 30.6 |
| Exacerbations in preceding 9 months (%) | 69.7 | 69.3 | 0.9 | 56.9 | 26.6 |
| Medication | |||||
| Short-acting bronchodilators (%) | 68.9 | 69.8 | 2.0 | 55.1 | 28.5 |
| Long-acting beta-2 sympathomimetics (%) | 71.1 | 70.5 | 1.2 | 53.9 | 36.0 |
| Long-acting anticholinergics (%) | 50.8 | 49.3 | 2.9 | 33.0 | 36.6 |
| Inhaled corticosteroids (%) | 44.1 | 44.8 | 1.3 | 36.9 | 14.7 |
| Other COPD-specific medication (%) | 5.0 | 5.5 | 2.4 | 3.8 | 6.1 |
| Oral corticosteroids | 18.4 | 18.2 | 0.5 | 5.9 | 39.0 |
| Other comorbidity causing dyspnea | |||||
| Bronchial asthma (%) | 11.0 | 10.9 | 0.4 | 9.6 | 4.8 |
| Other lung diseases (%) | 13.4 | 13.7 | 1.0 | 9.9 | 10.8 |
| Cardiac disease (%) | 30.3 | 28.3 | 4.4 | 28.8 | 3.2 |
| Structured training of COPD patients (%) | 19.7 | 19.3 | 0.8 | 14.5 | 13.7 |
| Long-term oxygen therapy (%) | 7.6 | 7.5 | 0.3 | 3.2 | 19.2 |
| Home ventilation (%) | 3.4 | 3.8 | 2.2 | 1.6 | 11.9 |
| Time to diagnosis in years (SD) | 10.2 (6.9) | 10.3 (7.1) | 1.3 | 9.1 (6.6) | 15.9 |
| Diagnostic test | |||||
| Reversibility with beta-2 sympathomimetics or anticholinergics*1, *2 (%) | 71.6 | 7 1.3 | 0.6 | 69.7 | 4.1 |
| Reversibility with glucocorticoids*1, *2 (%) | 13.3 | 12.8 | 1.4 | 10.7 | 7.9 |
| Elevated airway resistance *1, *3 (%) | 29.4 | 30.5 | 2.9 | 28.1 | 2.4 |
| Lung hyperinflation *1, *3 (%) | 21.2 | 22.0 | 1.9 | 18.9 | 5.7 |
| Gas exchange disorder *1, *3 (%) | 8.7 | 7.9 | 2.9 | 6.9 | 6.7 |
*1COPD-typical history and FEV1 < 80%; *2FEV1/VC ≤ 70% and increase in FEV1 < 15% and/or < 200 mL; *3if FEV1/VC > 70%
COPD, chronic obstructive pulmonary disease; SD, standard deviation; absolute STD, absolute standardized differences; FEV1, forced expiratory volume in 1 second; VC, vital capacity