Prevalence of ever-asthma# from age 8 to 28 years and distribution by age at asthma onset and sex
| All (n=3430) | Female (n=1679) | Male (n=1751) | p-value¶ | |
| Ever-asthma | 690 (20.1) | 349 (20.8) | 341 (19.5) | 0.338 |
| Age at asthma onset | ||||
| ≤8 years | 248 (35.9) | 105 (30.1) | 143 (41.9) | 0.061 |
| 9–13 years | 169 (24.5) | 78 (22.3) | 91 (26.7) | 0.547 |
| 14–19 years | 184 (26.7) | 116 (33.2) | 68 (19.9) | <0.001 |
| >19 years | 89 (12.9) | 50 (14.3) | 39 (11.4) | 0.156 |
Data are presented as n (%), unless otherwise stated. #: a report of physician-diagnosed asthma in any of the questionnaire surveys; ¶: difference by sex analysed by the Chi-squared test.