Table 2.
Demographic characteristics of the study population and the factors of adjusted myopia and control groups during the semester and holidays after adjustment.
| Control | Adjusted myopia | χ 2 | p (chi-square test) | p (logistic regression analysis) | OR | 95% CI | ||
|---|---|---|---|---|---|---|---|---|
| (N = 521) | (N = 521) | Lower | Upper | |||||
| Gender, male, N (%) | 317 (60.84) | 317 (60.84) | 0.000 | 1.000 | 0.506 | 1.098 | 0.834 | 1.444 |
| Parental myopia | ||||||||
| Father, N (%) | 104 (19.96) | 104 (19.96) | 0.000 | 1.000 | 0.920 | 1.017 | 0.737 | 1.402 |
| Mother, N (%) | 118 (22.65) | 118 (22.65) | 0.000 | 1.000 | 0.686 | 0.939 | 0.692 | 1.274 |
| Age (mean ± SD years) | 14.67 ± 1.66 | 14.84 ± 1.35 | 0.000 | 1.000 | ||||
| Junior group (11–14 years), N (%) | 163 (31.29) | 163 (31.29) | ||||||
| Senior group (15–18 years), N (%) | 358 (68.71) | 358 (68.71) | 0.621 | 0.927 | 0.688 | 1.251 | ||
| During the semester | ||||||||
| Average number of days per week participating in outdoor activities, N (%) | 3.230 | 0.072 | ||||||
| ≤2 days | 241 (46.26) | 270(51.82) | ||||||
| 3–7 days | 280 (53.74) | 251 (48.18) | 0.017 | 0.698 | 0.519 | 0.939 | ||
| Average number of hours spent on each outdoor activity session, N (%) | 5.507 | 0.064 | ||||||
| <Half an hour | 140 (26.87) | 128 (24.57) | 0.220 | |||||
| ≥Half an hour and < one hour | 217 (43.25) | 254 (48.75) | 0.224 | 1.239 | 0.877 | 1.751 | ||
| ≥One hour | 164 (31.48) | 139 (26.68) | 0.892 | 0.972 | 0.650 | 1.455 | ||
| Average number of hours per week of outdoor activities, N (%) | 0.467 | 0.494 | ||||||
| <3 hours | 285 (54.70) | 274 (52.59) | ||||||
| ≥3 hours | 236 (45.30) | 247 (47.41) | 0.073 | 1.338 | 0.973 | 1.841 | ||
| Average number of hours per week of indoor activities, N (%) | 0.601 | 0.438 | ||||||
| <3 hours | 412 (79.08) | 422 (81.00) | ||||||
| ≥3 hours | 109 (20.92) | 99 (19.00) | 0.530 | 0.887 | 0.611 | 1.289 | ||
| Mid-day nap, N (%) | 0.628 | 0.428 | ||||||
| Yes | 133 (25.53) | 122 (23.42) | 0.457 | 0.890 | 0.654 | 1.210 | ||
| No | 388 (74.47) | 399 (76.58) | ||||||
| Average number of hours per night of sleep, N (%) | 5.312 | 0.070 | ||||||
| <6 hours | 95 (18.24) | 78 (14.97) | 0.242 | |||||
| ≥6 hours and <8 hours | 331 (63.53) | 366 (70.25) | 0.114 | 1.370 | 0.927 | 2.026 | ||
| ≥8 hours | 95 (18.23) | 77 (14.78) | 0.524 | 1.183 | 0.705 | 1.984 | ||
| Average night bedtime, N (%) | 1.587 | 0.452 | ||||||
| Before 10 pm (excluding 10 pm) | 191 (36.66) | 177 (33.97) | 0.799 | |||||
| 10 pm-11 pm (excluding 11 pm) | 213 (40.88) | 233 (44.72) | 0.532 | 0.901 | 0.650 | 1.249 | ||
| After 11 pm (including 11 pm) | 117 (22.46) | 111 (21.31) | 0.896 | 0.972 | 0.634 | 1.490 | ||
| Average daily wake time, N (%) | 4.789 | 0.029 ∗ | ||||||
| Before 6 am (excluding 6 am) | 208 (39.92) | 243 (46.64) | ||||||
| After 6 am (including 6 am) | 313 (60.08) | 278 (53.36) | 0.047 ∗ | 0.761 | 0.581 | 0.997 | ||
| During holidays | ||||||||
| Average number of days per week participating in outdoor activities, N (%) | 0.346 | 0.556 | ||||||
| ≤2 days | 348 (66.79) | 339 (65.07) | ||||||
| 3–7 days | 173 (33.21) | 182 (34.93) | 0.254 | 1.189 | 0.883 | 1.600 | ||
| Average number of hours spent on each outdoor activity session, N (%) | 13.175 | 0.004 ∗ | ||||||
| <Half an hour | 119 (22.84) | 104 (19.96) | 0.015 ∗ | |||||
| ≥Half an hour and < one hour | 130 (24.95) | 138 (26.49) | 0.490 | 1.146 | 0.778 | 1.690 | ||
| ≥One hour and <2 hours | 122 (23.42) | 166 (31.86) | 0.054 | 1.516 | 0.993 | 2.317 | ||
| ≥2 hours | 150 (28.79) | 113 (21.69) | 0.522 | 0.861 | 0.543 | 1.364 | ||
| Average number of hours per week of outdoor activities, N (%) | 0.035 | 0.852 | ||||||
| <3 hours | 241 (46.26) | 244 (46.83) | ||||||
| ≥3 hours | 280 (53.74) | 277 (53.17) | 0.338 | 0.845 | 0.599 | 1.192 | ||
| Average number of hours per week of indoor activities, N (%) | 0.115 | 0.734 | ||||||
| <3 hours | 370 (71.02) | 365 (70.06) | ||||||
| ≥3 hours | 151 (28.98) | 156 (29.94) | 0.287 | 1.199 | 0.858 | 1.676 | ||
| Mid-day nap, N (%) | 0.042 | 0.837 | ||||||
| Yes | 148 (28.41) | 151 (28.98) | 0.716 | 1.055 | 0.791 | 1.406 | ||
| No | 373 (71.59) | 370 (71.02) | ||||||
| Average number of hours per night of sleep, N (%) | 1.496 | 0.683 | ||||||
| <6 hours | 43 (8.25) | 41 (7.87) | 0.947 | |||||
| ≥6 hours and <8 hours | 157 (30.13) | 165 (31.67) | 0.686 | 0.896 | 0.525 | 1.528 | ||
| ≥8 hours and <10 hours | 241 (46.26) | 248 (47.60) | 0.934 | 0.978 | 0.579 | 1.653 | ||
| ≥10 hours | 80 (15.36) | 67 (12.86) | 0.932 | 0.974 | 0.534 | 1.777 | ||
| Average night bedtime, N (%) | 14.506 | 0.002 ∗ | ||||||
| Before 10 pm (excluding 10 pm) | 138 (26.49) | 97 (18.62) | 0.003 ∗ | |||||
| 10 pm-11 pm (excluding 11 pm) | 150 (28.79) | 155 (29.75) | 0.019 ∗ | 1.570 | 1.076 | 2.289 | ||
| 11 pm-12 am (excluding 12 am) | 134 (25.72) | 180 (34.55) | <0.001 ∗ | 2.173 | 1.451 | 3.253 | ||
| After 12 am (including 12 am) | 99 (19.00) | 89 (17.08) | 0.021 ∗ | 1.786 | 1.093 | 2.919 | ||
| Average daily wake time, N (%) | 7.736 | 0.102 | ||||||
| Before 7 am (excluding 7 am) | 90 (17.28) | 76 (14.59) | 0.154 | |||||
| 7 am-8 am (excluding 8 am) | 108 (20.73) | 133 (25.53) | 0.105 | 1.417 | 0.929 | 2.161 | ||
| 8 am-9 am (excluding 9 am) | 126 (24.18) | 131 (25.14) | 0.898 | 1.029 | 0.665 | 1.592 | ||
| 9 am-10 am (excluding 10 am) | 94 (18.04) | 103 (19.77) | 0.604 | 1.132 | 0.709 | 1.808 | ||
| After 10 am (including 10 am) | 103 (19.77) | 78 (14.97) | 0.410 | 0.805 | 0.481 | 1.348 | ||
∗Statistical significance (p < 0.05).