Table 1. Baseline characteristics of the study population.
| No asthma, n=2398 (%) | Asthma, n=1394 (%) | Missing (%) | |
| Sex | 0.0 | ||
| Male | 912 (38.0) | 532 (38.2) | |
| Female | 1486 (62.0) | 862 (61.8) | |
| Age at baseline (in years) | 0.0 | ||
| ≤59 | 1506 (62.8) | 893 (64.1) | |
| 60–69 | 699 (29.1) | 862 (61.8) | |
| 70–79 | 166 (6.9) | 84 (6.0) | |
| ≥80 | 27 (1.1) | 16 (1.1) | |
| Age of asthma onset | 4.1 | ||
| <15 | – | 86 | |
| ≥15 | – | 1253 | |
| Pack years | 2.7 | ||
| 0 | 1308 (56.0) | 627 (46.3) | |
| ≤19 | 657 (28.1) | 453 (33.5) | |
| ≥20 | 371 (15.9) | 273 (20.2) | |
| BMI (kg × m−2) | 2.4 | ||
| Underweight (<18.5) | 26 (1.1) | 19 (1.4) | |
| Normal (18.5–24.99) | 998 (42.6) | 463 (34.0) | |
| Overweight (25–29.99) | 958 (40.9) | 577 (42.4) | |
| Obese (≥30) | 358 (15.3) | 303 (22.2) |
Lifetime tobacco exposure was calculated in pack- years (number of cigarettes per day/20× x number of years smoked, where 1 pipe=2.5 cigarettes and 1 cigar=4 cigarettes) uponon which individuals were divided into three groups: 0, ≤19 and ≥20 pack- years.
Body mass index (BMI) assessed as weight in kilograms divided by the square of the height in metersmetres, then divided into four categories according to World Health OrganizationWHO classification.