Characteristic | Baseline period | Intervention period | p-value |
Subjects | 830 | 890 | |
Age years | 45.9±17.4 | 47.3±17.2 | 0.084 |
Female | 602 (72.5) | 632 (71.0) | 0.519 |
Smoking status | 0.001 | ||
Nonsmoker | 411 (49.5) | 460 (51.7) | |
Ex-smoker | 161 (19.4) | 185 (20.8) | |
Current smoker | 124 (14.9) | 157 (17.6) | |
Not documented | 134 (16.1) | 88 (9.9) | |
Comorbidities | |||
Atopy | 331 (39.9) | 350 (39.3) | 0.285 |
COPD | 62 (7.5) | 68 (7.6) | 0.966 |
Other respiratory diagnosis | 16 (1.9) | 13 (1.5) | 0.573 |
Prior objective testing | |||
Spirometry | 529 (63.7) | 579 (65.1) | 0.600 |
Methacholine challenge | 74 (8.9) | 73 (8.2) | 0.658 |
Prior asthma care (since 2003) | |||
Seen by pulmonologist or allergist | 136 (16.4) | 158 (17.8) | 0.491 |
Seen in emergency room or hospitalised for asthma | 51 (6.1) | 38 (4.3) | 0.100 |
Baseline medications (first study visit)# | |||
Short-acting bronchodilator | 469 (56.5) | 544 (61.1) | 0.058 |
Inhaled corticosteroid alone¶ | 147 (17.7) | 173 (19.4) | 0.391 |
Inhaled corticosteroid with long-acting β-agonist | 125 (15.1) | 158 (17.8) | 0.150 |
Long-acting β-agonist alone | 6 (0.7) | 4 (0.4) | 0.669 |
Leukotriene receptor antagonist | 21 (2.5) | 26 (2.9) | 0.727 |
Long-acting muscarinic antagonist | 6 (0.7) | 13 (1.5) | 0.218 |
Prednisone+ | 8 (1.0) | 6 (0.7) | 0.689 |
Data are presented as n, mean±sd or n (%), unless otherwise stated. COPD: chronic obstructive pulmonary disease. #: formal assessment of asthma severity was not possible, as this requires knowledge of which medications are required to achieve good control and asthma control itself was not known for most patients (a breakdown of baseline medications by control status is provided in the supplementary material); ¶: without concurrent use of a long-acting β-agonist in a combination inhaler or as a separate inhaler; +: includes only those patients using prednisone chronically.