Characteristics of the study population
| Centres | ||||||||
| Reykjavik | Bergen | Aarhus# | Gothenburg | Uppsala | Umeå | Tartu | All | |
| Subjects n | 1969 | 2506 | 2608 | 2188 | 2572 | 2640 | 1708 | 16191 |
| Participation rate | 67.9 | 72.6 | 71.0 | 76.0 | 81.8 | 80.2 | 69.4 | 74.3 |
| Mean follow-up time yrs | 8.5 | 9.4 | 7.7 | 8.2 | 8.2 | 8.2 | 5.3 | 7.9 |
| Age yrs | 40.9±7.0 | 40.5±6.8 | 39.1±7.0 | 40.4±7.3 | 40.4±7.3 | 40.6±7.3 | 35.6±7.0 | 39.6±7.1 |
| BMI kg·m−2 | 25.3±4.0 | 24.7±4.0 | 24.3±4.2 | 25.0±3.9 | 24.6±3.9 | 25.2±4.3 | 24.2±4.2 | 24.8±4.0 |
| BMI ≥30 | 11.6 | 7.9 | 8.1 | 9.6 | 6.8 | 8.9 | 9.1 | 8.7 |
| Nocturnal GOR >1·week−1 | 5.2 | 7.7 | 6.7 | 11.2 | 7.4 | 8.2 | 7.4 | 7.7 |
| Snoring >3·week−1 | 20.7 | 16.9 | 17.7 | 20.4 | 18.6 | 20.7 | 12.0 | 18.1 |
| Onset of asthma | 4.4 | 3.8 | 4.0 | 4.3 | 4.2 | 4.9 | 1.3 | 3.9 |
| Onset of wheeze | 9.1 | 13.1 | 11.3 | 12.5 | 11.1 | 12.0 | 14.4 | 11.3 |
| Onset of night-time symptoms | 7.4 | 9.5 | 8.0 | 8.2 | 8.9 | 13.8 | 9.3 | |
Data are presented as mean±sd or per cent, unless otherwise stated
BMI: body mass index
GOR: gastro-oesophageal reflux
#: incomplete data