2.1. Participants
This is a cross-sectional study performed in kindergarten children and
school students from China. Medical examination at child care department
or school health school students, aged 3 to 17 ages healthy children.
Informed consent was obtained from the parents or legal guardians of the
children. Exclusion criteria: ① Respiratory tract infection occurred
within 4 weeks before inclusion; ②patients with congenital heart
disease, respiratory system, neuromuscular system, immune system and
other diseases; ③ a family history of asthma; ④ cannot cooperate with
the completion of pulse oscillation lung function detection; ⑤ abnormal
pulmonary ventilation function; ⑥ There are smokers in the family. A
total of 7000 children were enrolled in the study. This study was
approved by the Ethics Committee of Shanghai Children’s Medical Center
(Ethics No: SCMCIRB-K2017007), and all branches followed the ethics of
the main research unit. The age of enrolled children ranged 4 to 17
years and their body height ranged 100 to 189 cm.