Table 2 Univariate analysis of associated factors with the myopia onset
Variable | Total, mean or n | Myopia, mean or n (%) | Non-myopia, mean or n (%) | P |
|---|---|---|---|---|
Height (cm) | 138.76 ± 11.80 | 143.43 ± 10.56 | 138.14 ± 11.82 |  < 0.01 |
Weight (kg) | 34.24 ± 10.29 | 36.92 ± 9.64 | 33.88 ± 10.32 |  < 0.01 |
Parental myopia |  < 0.01 | |||
 None | 1235 | 98 (7.9%) | 1137 (92.1%) |  |
 Father | 347 | 56 (16.1%) | 291 (83.9%) |  |
 Mother | 421 | 62 (14.7%) | 359 (85.3%) |  |
 Both parents | 218 | 44 (20.2%) | 174 (79.8%) |  |
Education level of the father | 0.04 | |||
 Doctor or master | 37 | 9 (24.3%) | 28 (75.7%) |  |
 Bachelor | 448 | 57 (12.7%) | 391 (87.3%) |  |
 Below bachelor | 1736 | 194 (11.2%) | 1542 (88.8%) |  |
Education level of the mother | Â | Â | Â | 0.01 |
 Doctor or master | 26 | 6 (23.1%) | 20 (76.9%) |  |
 Bachelor | 330 | 51 (15.5%) | 279 (84.5%) |  |
 Below bachelor | 1865 | 203 (10.9%) | 1662 (89.1%) |  |
Academic level | Â | Â | Â | 0.02 |
 Unqualified (grade D) | 313 | 25 (8.0%) | 288 (92.0%) |  |
 Qualified (grade C) | 798 | 88 (11.0%) | 710 (89.0%) |  |
 Good (grade B) | 844 | 105 (12.4%) | 739 (87.6%) |  |
 Excellent (grade A) | 266 | 42 (15.8%) | 224 (84.2%) |  |
Hours of homework per day on school days | 0.03 | |||
  < 1 h | 264 | 20 (7.6%) | 244 (92.4%) |  |
 1–2 h | 972 | 105 (10.8%) | 867 (89.2%) |  |
 2–3 h | 664 | 89 (13.4%) | 575 (86.6%) |  |
  > 3 h | 321 | 46 (14.3%) | 275 (85.7%) |  |
Hours of homework per day on weekends |  < 0.01 | |||
  < 1 h | 215 | 19 (8.8%) | 196 (91.2%) |  |
 1–2 h | 729 | 63 (8.6%) | 666 (91.4%) |  |
 2–3 h | 723 | 91 (12.6%) | 632 (87.4%) |  |
  > 3 h | 554 | 87 (15.7%) | 467 (84.3%) |  |
Number of after-school tutoring per week |  < 0.01 | |||
 0 | 851 | 63 (7.4%) | 788 (92.6%) |  |
 1–2 times | 1034 | 135 (13.1%) | 899 (86.9%) |  |
 3–4 times | 262 | 49 (18.7%) | 213 (81.3%) |  |
  > 4 times | 74 | 13 (17.6%) | 61 (82.4%) |  |
Frequency of extracurricular reading |  < 0.01 | |||
 Never | 34 | 4 (11.8%) | 30 (88.2%) |  |
 Sometimes | 963 | 89 (9.2%) | 874 (90.8%) |  |
 Often | 950 | 123 (12.9%) | 827 (87.1%) |  |
 Always | 274 | 44 (16.1%) | 230 (83.9%) |  |
Frequency of visual health education from parents |  < 0.01 | |||
 Always | 296 | 48 (16.2%) | 248 (83.8%) |  |
 Often | 796 | 112 (14.1%) | 684 (85.9%) |  |
 Sometimes | 860 | 76 (8.8%) | 784 (91.2%) |  |
 Never | 269 | 24 (8.9%) | 245 (91.1%) |  |
Sitting posture during learning | Â | |||
 Correct | 1581 | 149 (9.4%) | 1432 (90.6%) |  |
 Incorrect | 640 | 111 (17.3%) | 529 (82.7%) |  |
Frequency of lying down reading |  < 0.01 | |||
 Always | 48 | 7 (14.6%) | 41 (85.4%) |  |
 Often | 340 | 63 (18.5%) | 277 (81.5%) |  |
 Sometimes | 1317 | 147 (11.2%) | 1170 (88.8%) |  |
 Never | 516 | 43 (8.3%) | 473 (91.7%) |  |
Frequency of feeling eye fatigue |  < 0.01 | |||
 Never | 692 | 32 (4.6%) | 660 (95.4%) |  |
 Sometimes | 1313 | 152 (11.6%) | 1161 (88.4%) |  |
 Often | 187 | 65 (34.8%) | 122 (65.2%) |  |
 Always | 29 | 11 (37.9%) | 18 (62.1%) |  |
Time of going to sleep at night | 0.02 | |||
 Before 9 o'clock | 433 | 33 (7.6%) | 400 (92.4%) |  |
 9–10 o'clock | 1437 | 175 (12.2%) | 1262 (87.8%) |  |
 10–11 o'clock | 330 | 50 (15.2%) | 280 (84.8%) |  |
 11–12 o'clock | 15 | 1 (6.7%) | 14 (93.3%) |  |
 After 12 o'clock | 6 | 1 (16.7%) | 5 (83.3%) |  |
Frequency of fish intake in the diet | 0.03 | |||
 Never | 294 | 43 (14.6%) | 251 (85.4%) |  |
 Sometimes | 964 | 108 (11.2%) | 856 (88.8%) |  |
 Often | 805 | 82 (10.2%) | 723 (89.8%) |  |
 Always | 158 | 27 (17.1%) | 131 (82.9%) |  |
Performing the Chinese eye exercises regularly |  < 0.01 | |||
 Yes | 1719 | 180 (10.5%) | 1539 (89.5%) |  |
 No | 502 | 80 (15.9%) | 422 (84.1%) |  |
Frequency of using electronic devices after turning off the lights at night |  < 0.01 | |||
 Always | 11 | 0 (0.0%) | 11 (100.0%) |  |
 Often | 23 | 8 (34.8%) | 15 (65.2%) |  |
 Sometimes | 410 | 59 (14.4%) | 351 (85.6%) |  |
 Never | 1777 | 193 (10.9%) | 1584 (89.1%) |  |
The most frequent place to go on weekends |  < 0.01 | |||
 Sports venues | 407 | 40 (9.8%) | 367 (90.2%) |  |
 Leisure or entertainment places | 333 | 23 (6.9%) | 310 (93.1%) |  |
 Learning places | 643 | 105 (16.3%) | 538 (83.7%) |  |
 Staying at home | 838 | 92 (11.0%) | 746 (89.0%) |  |
Joining sports training teams | 0.03 | |||
 Yes | 744 | 72 (9.7%) | 672 (90.3%) |  |
 No | 1477 | 188 (12.7%) | 1289 (87.3%) |  |
Main exercise content | 0.04 | |||
 Strength training | 6 | 2 (33.3%) | 4 (66.7%) |  |
 Jogging | 423 | 58 (13.7%) | 365 (86.3%) |  |
 Ball games | 473 | 42 (8.9%) | 431 (91.1%) |  |
 Uncertain | 1319 | 158 (12.0%) | 1161 (88.0%) |  |
Hours of outdoor activities per day on school days |  < 0.01 | |||
 Less than 1 h | 1079 | 155 (14.4%) | 924 (85.6%) |  |
 1–2 h | 792 | 81 (10.2%) | 711 (89.8%) |  |
 2–3 h | 250 | 18 (7.2%) | 232 (92.8%) |  |
 More than 3 h | 100 | 6 (6.0%) | 94 (94.0%) |  |
Hours of outdoor activities per day on weekends |  < 0.01 | |||
 Less than 1 h | 599 | 81 (13.5%) | 518 (86.5%) |  |
 1–2 h | 892 | 119 (13.3%) | 773 (86.7%) |  |
 2–3 h | 490 | 44 (9.0%) | 446 (91.0%) |  |
 3–4 h | 119 | 9 (7.6%) | 110 (92.4%) |  |
 More than 4 h | 121 | 7 (5.8%) | 114 (94.2%) |  |