Study Questionnaire
The information on doctor diagnosed asthma among participants was
collected by the Chinese version of Epidemiologic Standardization
Project Questionnaire of the American Thoracic Society (ATS-DLD-78-A),
which were completed by parents or guardians. Doctor diagnosed asthma
was defined by the question “Has a doctor ever diagnosed this child
with asthma?” In addition, asthma for family members was also collected
by the questions “Has this child’s father ever had asthma?”, “Has
this child’s mother ever had asthma?”, “Has this child’s paternal
grandfather ever had asthma?”, “Has this child’s paternal grandmother
ever had asthma?”, “Has this child’s maternal grandfather ever had
asthma?” and “Has this child’s maternal grandmother ever had
asthma?”. According to the total number of family members affected by
asthma, participants were classified into four groups, no family member
affected, 1 family member affected, 2 family members affected and ≥ 3
family members affected.