Demographic and socioeconomic characteristics of the respondents
| Boys | Girls | p Value | |
| n=3260 | n=3187 | ||
| Age, years | 9.2 (1.8) | 9.2 (1.8) | 0.798 |
| Height, cm | 134 (13.5) | 134 (13.2) | 0.539 |
| Weight, kg | 31.7 (9.7) | 30.3 (8.9) | <0.0001 |
| Body mass index, kg/m2 | 17.3 (3.3) | 16.5 (2.8) | <0.0001 |
| No of family members | 4.6 (1.2) | 4.5 (1.1) | 0.002 |
| No of siblings | 1.3 (1.1) | 1.2 (1.0) | <0.0001 |
| Household area per person, sq ft | 127.4 (56.1) | 123.3 (56.6) | 0.006 |
| Allergic rhinitis, % | 50.1 | 38.9 | <0.0001 |
| Asthma, % | 6.5 | 4.0 | <0.0001 |
| Nocturnal oral breathing,* % | 12.0 | 7.5 | <0.0001 |
| Nocturnal sweating,* % | 15.8 | 7.7 | <0.0001 |
| Snoring,* % | 19.6 | 12.3 | <0.0001 |
| Weight group, % | <0.0001 | ||
| Overweight | 16.3 | 12.3 | |
| Obese | 11.5 | 9.5 | |
| Family income, % | 0.004 | ||
| ≤HK$10 000 | 28.8 | 32.3 | |
| HK$10 001–15 000 | 22.3 | 22.8 | |
| >HK$15 000 | 48.8 | 44.9 | |
| Household area, % | 0.116 | ||
| ≤400 sq ft | 30.7 | 32.8 | |
| 401–600 sq ft | 32.9 | 32.8 | |
| >600 sq ft | 36.4 | 34.3 | |
| Paternal education, % | <0.0001 | ||
| Primary or below | 18.4 | 19.1 | |
| Secondary | 63.8 | 67.3 | |
| Tertiary or above | 17.8 | 13.7 | |
| Maternal education, % | 0.008 | ||
| Primary or below | 18.6 | 20.3 | |
| Secondary | 70.3 | 70.8 | |
| Tertiary or above | 11.1 | 8.9 |
↵* Symptoms were considered to be positive if reported to be present for at least one night per week in the past 12 months.