2 | MATERIALS AND METHODS

2.1 | Study sample

A cross-sectional survey was performed in Chengdu, Sichuan Province in Southwest China. Four districts were chosen for participant recruitment, including a country village, a town, a county seat, and a city. Two kindergartens, two primary schools, and two junior middle schools from each district were randomly chosen to participate and the questionnaire was voluntarily completed by the children’s guardians. The sample was children aged 2–14 years. Children with a history of neuromuscular disease, craniofacial syndromes, cerebral palsy, sickle cell disease, mucopolysaccharide storage disease, or immunodeficiency were excluded. Participants were also excluded if they had mental or physical impairment severe enough to cause abnormal behaviors, including congenital disease, intellectual disability, or a psychiatric disorder. The study was approved by the Biomedical Research Ethics Committee of the West China Hospital of Sichuan University. Written informed consent was obtained from each guardian before completing the questionnaire.

2.2 | Questionnaire

The investigators explained the purpose of the study and administered informed consent before administering the questionnaire. The following items from our parent-report questionnaire were used for analyses: (1) demographic factors including age, sex, race, weight, height, and district (city, suburb, county seat, town, or countryside village); (2) socioeconomic factors including family income and parental education; (3) delivery method (natural labor, Cesarean section), gestational age (premature birth, full-term birth, post-term birth), parental age at delivery, maternal pregnancy disease, and parental history of obstructive sleep apnea hypopnea syndrome; (4) symptoms of upper respiratory tract infection during the past six months, including tonsillitis, chronic rhinosinusitis, AR, and asthma; (5) passive smoke exposure (child exposed to secondhand smoke), maternal smoking and secondhand smoke exposure during the child’s gestation; (6) and snoring; based on the OSA-5 survey7, participants were divided into three groups for comparisons (non-snorers = “never”, occasional snorers = “rarely” or “sometimes”, and habitual snorers = “frequently” or “all the time.”

2.3 | Data analysis

All analyses were performed using SPSS version 22.0. Data are presented as mean ± SD, median (interquartile range), and percent, for parametric, nonparametric, and categorical data, respectively. Parametric and nonparametric variables were compared using one-way analysis of variance and Mann–Whitney tests. Categorical variables were compared using χ2 tests. Multivariate logistic regression analyses were subsequently performed to further confirm the association between potential risk factors and HS. The association was assessed in logistic regression models adjusted for age, sex, and BMI.