Table 7.
Relationships between baseline usual bedtime and potential variables.
| Variables | Category | Slept before 9:30 p.m. | Slept at 9:30 p.m. and after | Unadjusted OR (95% CI) | p-value | ||
|---|---|---|---|---|---|---|---|
| N | % (row) | N | % (row) | ||||
| Residency area | Sub-urban | 3657 | 75.86% | 1164 | 24.14% | 1 (Reference) | |
| Urban | 688 | 56.77% | 524 | 43.23% | 2.39 | p < 0.001 | |
| Age (years) | 6 | 1432 | 74.31% | 495 | 25.69% | 1 (Reference) | |
| 7 | 2114 | 70.96% | 865 | 29.04% | 1.18 (1.04, 1.35) | p = 0.01 | |
| 8 | 799 | 70.90% | 328 | 29.10% | 1.19 (1.01, 1.40) | p = 0.04 | |
| Gender | Male | 2311 | 72.17% | 891 | 27.83% | 1 (Reference) | |
| Female | 2034 | 71.87% | 796 | 28.13% | 1.02 (0.91, 1.14) | p = 0.80 | |
| Myopic parent | 0 | 1927 | 75.99% | 609 | 24.01% | 1 (Reference) | |
| 1 | 1428 | 69.90% | 615 | 30.10% | 1.36 (1.20, 1.56) | p < 0.001 | |
| 2 | 769 | 66.46% | 388 | 33.54% | 1.60 (1.37, 1.86) | p < 0.001 | |
| Parent education | Lower than undergrad | 2823 | 76.36% | 874 | 23.64% | 1 (Reference) | |
| Undergrad | 1322 | 65.77% | 688 | 34.23% | 1.68 (1.49, 1.89) | p < 0.001 | |
| Postgrad | 140 | 56.22% | 109 | 43.78% | 2.51 (1.94, 3.27) | p < 0.001 | |
|
Usual wake-up time Sleep duration (hours) |
Before 6:30 a.m. | 1657 | 89.62% | 192 | 10.38% | 1 (Reference) | |
| 6:30 to 6:59 a.m. | 1862 | 71.70% | 735 | 28.30% | 3.41 (2.87, 4.05) | p < 0.001 | |
| 7 a.m. and after | 826 | 52.05% | 761 | 47.95% | 7.95 (6.65, 9.51) | p < 0.001 | |
| < 9.5 | 1215 | 48.76% | 1277 | 51.24% | 1 (Reference) | ||
| ≥ 9.5 and < 10 | 1587 | 80.27% | 390 | 19.73% | 0.23 (0.20, 0.27) | p < 0.001 | |
| ≥ 10 h | 1543 | 98.66% | 21 | 1.34% | 0.01 (0.01, 0.02) | p < 0.001 | |
| Reading time weekly total | 15.93 ± 6.79 | 17.14 ± 7.24 | 1.03 (1.02, 1.03) | p < 0.001 | |||
| Screen time weekly total | 6.70 ± 3.80 | 6.94 ± 4.02 | 1.02 (1.00, 1.03) | p = 0.03 | |||
| Outdoor time weekly total | 7.32 ± 3.85 | 6.97 ± 3.87 | 0.98 (0.96, 0.99) | p = 0.002 | |||