Table 1.
Demographic characteristics of the study population and the factors of the myopia and nonmyopia groups during the semester and holidays.
| Nonmyopia | Myopia | χ 2 | p (chi-square test) | p (logistic regression analysis) | OR | 95% CI | ||
|---|---|---|---|---|---|---|---|---|
| (N = 585) | (N = 1246) | Lower | Upper | |||||
| Gender, male, N (%) | 361 (61.71) | 623 (50.00) | 21.956 | <0.001 ∗ | 0.002 ∗ | 0.693 | 0.549 | 0.876 |
| Parental myopia | ||||||||
| Father, N (%) | 104 (17.78) | 487 (39.09) | 82.682 | <0.001 ∗ | <0.001 ∗ | 2.463 | 1.900 | 3.193 |
| Mother, N (%) | 118 (20.17) | 578 (46.39) | 112.490 | <0.001 ∗ | <0.001 ∗ | 2.853 | 2.232 | 3.646 |
| Age (mean ± SD, years) | 14.53 ± 1.66 | 15.10 ± 1.21 | 53.030 | <0.001 ∗ | ||||
| Junior group (11–14 years), N (%) | 227 (38.80) | 280 (22.47) | ||||||
| Senior group (15–18 years), N (%) | 358 (61.20) | 966 (77.53) | <0.001 ∗ | 2.216 | 1.720 | 2.855 | ||
| During the semester | ||||||||
| Average number of days per week participating in outdoor activities, N (%) | 6.864 | 0.009 ∗ | ||||||
| ≤2 days | 271 (46.32) | 659 (52.89) | ||||||
| 3–7 days | 314 (53.68) | 587 (47.11) | 0.033 ∗ | 0.764 | 0.597 | 0.978 | ||
| Average number of hours spent on each outdoor activity session, N (%) | 16.150 | <0.001 ∗ | ||||||
| <Half an hour | 149 (25.47) | 328 (26.32) | 0.139 | |||||
| ≥Half an hour and < one hour | 253 (43.25) | 634 (50.88) | 0.198 | 1.212 | 0.904 | 1.624 | ||
| ≥One hour | 183 (31.28) | 284 (22.80) | 0.753 | 0.946 | 0.671 | 1.334 | ||
| Average number of hours per week of outdoor activities, N (%) | 0.016 | 0.900 | ||||||
| <3 hours | 315 (53.85) | 667 (53.53) | ||||||
| ≥3 hours | 270 (46.15) | 579 (46.47) | 0.046∗ | 1.320 | 1.006 | 1.732 | ||
| Average number of hours per week of indoor activities, N (%) | 1.468 | 0.226 | ||||||
| <3 hours | 464 (79.32) | 1018 (81.70) | ||||||
| ≥3 hours | 121 (20.68) | 228 (18.30) | 0.925 | 0.985 | 0.713 | 1.359 | ||
| Mid-day nap, N (%) | 2.440 | 0.118 | ||||||
| Yes | 142 (24.27) | 262 (21.03) | 0.068 | 0.781 | 0.598 | 1.019 | ||
| No | 443 (75.73) | 984 (78.97) | ||||||
| Average number of hours per night of sleep, N (%) | 22.093 | <0.001 ∗ | ||||||
| <6 hours | 98 (16.75) | 218 (17.50) | 0.260 | |||||
| ≥6 hours and <8 hours | 371 (63.42) | 883 (70.87) | 0.188 | 1.249 | 0.897 | 1.739 | ||
| ≥8 hours | 116 (19.83) | 145 (11.63) | 0.879 | 1.035 | 0.666 | 1.608 | ||
| Average night bedtime, N (%) | 20.636 | <0.001 ∗ | ||||||
| Before 10 pm (excluding 10 pm) | 220 (37.61) | 338 (27.13) | 0.775 | |||||
| 10 pm-11 pm (excluding 11 pm) | 244 (41.71) | 607 (48.71) | 0.996 | 1.001 | 0.756 | 1.326 | ||
| After 11 pm (including 11 pm) | 121 (20.68) | 301 (24.16) | 0.554 | 1.118 | 0.773 | 1.617 | ||
| Average daily wake time, N (%) | 13.738 | <0.001 ∗ | ||||||
| Before 6 am (excluding 6 am) | 229 (39.15) | 603 (48.39) | ||||||
| After 6 am (including 6 am) | 356 (60.85) | 643 (51.61) | 0.037 ∗ | 0.782 | 0.621 | 0.985 | ||
| During holidays | ||||||||
| Average number of days per week participating in outdoor activities, N (%) | 0.007 | 0.933 | ||||||
| ≤2 days | 381 (65.13) | 809 (64.93) | ||||||
| 3–7 days | 204 (34.87) | 437 (35.07) | 0.136 | 1.214 | 0.941 | 1.566 | ||
| Average number of hours spent on each outdoor activity session, N (%) | 24.048 | <0.001 ∗ | ||||||
| <Half an hour | 128 (21.88) | 277 (22.23) | 0.035∗ | |||||
| ≥Half an hour and < one hour | 144 (24.62) | 373 (29.94) | 0.742 | 1.056 | 0.762 | 1.464 | ||
| ≥One hour and <2 hours | 144 (24.62) | 359 (28.81) | 0.507 | 1.129 | 0.789 | 1.615 | ||
| ≥2 hours | 169 (28.88) | 237 (19.02) | 0.096 | 0.719 | 0.487 | 1.061 | ||
| Average number of hours per week of outdoor activities, N (%) | 0.760 | 0.383 | ||||||
| <3 hours | 268 (45.81) | 598 (47.99) | ||||||
| ≥3 hours | 317 (54.19) | 648 (52.01) | 0.521 | 0.909 | 0.680 | 1.216 | ||
| Average number of hours per week of indoor activities, N (%) | 0.255 | 0.614 | ||||||
| <3 hours | 414 (70.77) | 896 (71.91) | ||||||
| ≥3 hours | 171 (29.23) | 350 (28.09) | 0.469 | 1.114 | 0.832 | 1.492 | ||
| Mid-day nap, N (%) | 1.938 | 0.164 | ||||||
| Yes | 168 (28.72) | 398 (31.94) | 0.063 | 1.259 | 0.987 | 1.605 | ||
| No | 417 (71.28) | 848 (68.06) | ||||||
| Average number of hours per night of sleep, N (%) | 4.579 | 0.205 | ||||||
| <6 hours | 46 (7.86) | 83 (6.66) | 0.892 | |||||
| ≥6 hours and <8 hours | 169 (28.90) | 415 (33.31) | 0.873 | 1.039 | 0.650 | 1.661 | ||
| ≥8 hours and <10 hours | 281 (48.03) | 584 (46.87) | 0.740 | 1.081 | 0.682 | 1.715 | ||
| ≥10 hours | 89 (15.21) | 164 (13.16) | 0.503 | 1.198 | 0.705 | 2.035 | ||
| Average night bedtime, N (%) | 42.891 | <0.001 ∗ | ||||||
| Before 10 pm (excluding 10 pm) | 155 (26.50) | 188 (15.09) | 0.002 ∗ | |||||
| 10 pm-11 pm (excluding 11 pm) | 172 (29.40) | 422 (33.87) | 0.012 ∗ | 1.516 | 1.095 | 2.100 | ||
| 11 pm-12 am (excluding 12 am) | 150 (25.64) | 438 (35.15) | <0.001 ∗ | 1.966 | 1.383 | 2.795 | ||
| After 12 am (including 12 am) | 108 (18.46) | 198 (15.89) | 0.071 | 1.479 | 0.967 | 2.263 | ||
| Average daily wake time, N (%) | 11.160 | 0.025 ∗ | ||||||
| Before 7 am (excluding 7 am) | 100 (17.09) | 168 (13.49) | 0.165 | |||||
| 7 am-8 am (excluding 8 am) | 121 (20.68) | 316 (25.36) | 0.059 | 1.423 | 0.986 | 2.053 | ||
| 8 am-9 am (excluding 9 am) | 142 (24.27) | 320 (25.68) | 0.555 | 1.120 | 0.770 | 1.629 | ||
| 9 am-10 am (excluding 10 am) | 107 (18.30) | 244 (19.58) | 0.225 | 1.284 | 0.857 | 1.925 | ||
| After 10 am (including 10 am) | 115 (19.66) | 198 (15.89) | 0.819 | 0.950 | 0.615 | 1.469 | ||
∗Statistical significance (p < 0.05).