Table 1 Definitions of the main outcome in the present study
Outcome
Asthma was defined as at least two of the following three criteria positive:
    (1) Dyspnoea, chest tightness and/or wheezing from 0 to 3 years and/or from 4 to 10 years of age
    (2) Doctor diagnosed asthma
    (3) Used asthma medication (inhaled corticosteroids, β2 agonists, sodium cromoglycate, leucotriene antagonists and/or aminophylline) at 0–3 years and/or 4–10 years of age
Current asthma was defined as asthma (see above) plus at least one of the following criteria positive:
    (1) Dyspnoea, chest tightness and/or wheezing during the past 12 months
    (2) Use of asthma medication during the past 12 months
    (3) Positive exercise test