3 | RESULTS

3.1 | Participant characteristics and prevalence of habitual snorers

Of the 1721 children enrolled, 197 questionnaires were excluded because: (1) the questionnaire was completed irregularly; (2) the child had a history of neuromuscular disease, craniofacial syndrome, cerebral palsy, sickle cell disease, mucopolysaccharide storage disease, or immunodeficiency; (3) the child had a mental or physical impairment severe enough to cause abnormal behaviors (including congenital disease, intellectual disability, or psychiatric disorder). The final 1524 questionnaires used for analyses represented a response rate of 88.56%. The survey included 926 boys and 622 girls. The sample’s average age was 7.11 ± 5.25 years, ranging from 2–14 years. Among these participants, 730, 282, 314, 119, and 103 lived in a city, a suburb, a county seat, a town, and a countryside village, respectively. Overall, there were 463 habitual snorers (30.38%), 683 occasional snorers (44.82%), and 402 non-snorers (26.38%).

3.2 | Risk factors for HS

3.2.1 | Social demography

Social demographic risk factors were tabulated for each group and are shown in Table 1. HS morbidity was significantly higher in preschool children (<7 years old) than in school children (≥7 years old). Though boys (31.53%, 292/926) had a slightly higher rate of HS than girls (27.49%, 171/622), this difference was not statistically significant.
Fewer minority nationality children (2.6%) than Han (97.4%) participated, though there was no race difference in HS prevalence. Nor did HS morbidity differ based on living district (Table 1).
BMI scores were 16.62 (15.12–19.80), 16.63 (15.08–19.72), and 16.59 (15.15–19.96) for the HS group, occasional snoring group, and non-snoring group, respectively. Adjusting for age and gender, BMI did not differ among the snoring groups.

3.2.2 | Socioeconomic factors

According to the average household income statistics of Sichuan Province in 2019, we divided family monthly earning into six groups. No significant difference was found between the prevalence of HS and family monthly earning (p = .21).
Paternal education did not differ between snoring groups (p = .119). Higher maternal education was associated with greater HS prevalence (p = .023); maternal college and undergraduate degrees were related to an increase in HS morbidity (2.3; 95% CI, 1.1–4.7).

3.2.3 | Birth and heredity information

Neither delivery method (natural labor vs. cesarean section) nor gestational age (premature, full-term, or post-term birth) was related to HS prevalence (p = .75 and .11, respectively). Nor were maternal or paternal ages at the child’s birth related to HS prevalence (p = .123 and .373, respectively).
In our sample, 77 mothers had pregnancy complications, including three highly prevalent diseases: diabetes, hypertension, and hypothyroidism. Interestingly, the prevalence of HS in children born to mothers with triple pregnancy complications was significantly lower compared with occasional and non-snoring (Table 2).
The average breastfeeding duration for the overall sample was 6.92 ± 5.51 months. The between-groups difference in average breastfeeding duration was statistically significant (p = .019). Breastfeeding duration (6.07 ± 5.22 months) in the HS group was significantly shorter than in the occasional snoring group (8.25 ± 5.91 months) and the non-snoring group (7.92 ± 6.12 months).
Parental loud snoring (considered a hereditary factor) was related to the HS prevalence (p < .001) (1.16; 95% CI, 1.29–1.61).

3.2.4 | History of upper respiratory inflammation

The prevalence of AR, nasosinusitis, and tonsillitis symptoms in the past six months for the HS, occasional, and non-snoring groups are listed in Table 3. AR symptoms (1.24; 95% CI, 1.10–1.77), nasosinusitis symptoms (17.62; 95% CI, 6.41–48.80), tonsillitis symptoms (19.66; 95% CI, 9.51–55.38), and pneumonia/bronchitis symptoms (14.22; 95% CI, 5.42–38.01) within the past six months were related to HS incidence. However, only 20 (1.3%) of the children had been diagnosed with asthma, which was unrelated to HS prevalence.

3.2.5 | Passive smoking exposure

In the HS group, the proportion of mothers with a history of smoking during pregnancy (43.1%) was markedly higher than that in the non-snoring (4.7%) and occasional snoring (2%) groups. Both maternal exposure to secondhand smoke during pregnancy and child exposure were related to HS prevalence (p < .00) (Table 4). To further investigate the relation between passive smoking and other factors and snoring, multivariate logistic regression analysis was undertaken, controlling for the potential confounders of age, gender, and upper respiratory inflammation in the fully adjusted model. Maternal smoking during pregnancy (1.95; 95% CI, 1.63–2.34), maternal exposure to secondhand smoke during pregnancy (1.61; 95% CI, 1.08–2.39), and child exposure to secondhand smoke (1.89; 95% CI, 1.56–2.23) were significant risk factors for HS.