Table 1 showed the basic characteristics of this sampling. The self-reported myopia rate of children and adolescents (mean age = 12.44, SD = 3.47) in Shenzhen was 49.8% (15, 026/30, 188),,and the myopia rate of female students (54.2%) was higher than that of male students (46.3%), and the difference was statistically significant; the self-reported myopia rates among primary, junior high and senior high students were 25.6%, 62.4%, 75.7%, respectively, which increased with the grade, and the difference was statistically significant; the myopia rate of students with higher father and mother education level was lower, and the myopia rate of students with poor family economic level was lower, and the difference was statistically significant.
Table 1
Basic characteristics of the samples.
Variables | Number of participants | Myopia cases | Myopia rates (%) | χ2 or χ2-trend | P value |
Sex | | | | 190.00a | < 0.001 |
Male | 16,897 | 7,816 | 46.3 | | |
Female | 13,291 | 7,210 | 54.2 | | |
Age (years) | | | | 5302.51a | < 0.001 |
≤ 12 | 14,484 | 4,049 | 28.0 | | |
> 12 | 15,704 | 10,977 | 69.9 | | |
Grade | | | | 5958.23b | < 0.001 |
Primary | 13,420 | 3,431 | 25.6 | | |
Junior high | 8,232 | 5,137 | 62.4 | | |
Senior high | 8,536 | 6,458 | 75.7 | | |
Family economic level | | | | 1127.34b | < 0.001 |
Under moderate | 4,113 | 1,598 | 38.9 | | |
Moderate | 20,395 | 10,494 | 51.5 | | |
Over moderate | 5,680 | 2,934 | 51.7 | | |
Father’s education | | | | 52.49b | < 0.001 |
Junior high or below | 9,641 | 5,025 | 52.1 | | |
Senior high | 11,387 | 5,712 | 50.2 | | |
College or above | 9,160 | 4,289 | 46.8 | | |
Mother’s education | | | | 119.86b | < 0.001 |
Junior high or below | 12,203 | 6,448 | 52.8 | | |
Senior high | 11,184 | 5,554 | 49.7 | | |
College or above | 68,01 | 3,024 | 44.5 | | |
Father myopia | | | | 444.10b | < 0.001 |
Yes | 8,414 | 4,936 | 58.7 | | |
No | 20,791 | 9,503 | 45.7 | | |
Unknown | 983 | 587 | 59.7 | | |
Mother myopia | | | | 164.62b | < 0.001 |
Yes | 8,696 | 4,955 | 57.0 | | |
No | 2,0524 | 9,525 | 46.4 | | |
Unknown | 968 | 546 | 56.4 | | |
Outdoor activity | | | | 26.66b | < 0.001 |
< 1h/d | 12785 | 6661 | 52.1 | | |
1-2h/d | 10284 | 4873 | 47.4 | | |
≥ 2h/d | 7102 | 3479 | 49.0 | | |
Screen time | | | | 140.73b | < 0.001 |
< 1h/d | 15853 | 7492 | 47.3 | | |
1-2h/d | 7925 | 3918 | 49.4 | | |
≥ 2h/d | 6410 | 3616 | 56.4 | | |
Academic record | | | | 148.18b | < 0.001 |
Bad | 7,580 | 3,494 | 46.1 | | |
Normal | 11,573 | 8,627 | 49.1 | | |
Good | 5,035 | 2,905 | 57.7 | | |
Study burden | | | | 397.40b | < 0.001 |
Light | 2,451 | 1,035 | 42.2 | | |
Normal | 19,020 | 8,847 | 46.5 | | |
Heavy | 8,717 | 5,144 | 59.0 | | |
Note: a is for χ2, b is for χ2-trend |
Table 2 showed the outcome of univariate analysis for sleep status and self-reported myopia. The self-reported myopia rates of students with night sleep duration ≥ 9, 8-9h/d, 7–8 and < 7h/d were 26.0%, 27.8%, 43.2%, and 68.6%, respectively, which increased with the decrease of night sleep duration (P < 0,001). And the effect of social jet lag on myopia was significant (all P value < 0.001). After subgroup analysis were performed by grade, in the primary school group, not falling asleep at a fixed time at night, not getting up at a fixed time in the morning, putting off falling asleep ≥ 2h/d on weekends, and putting off getting up ≥ 2h/d on weekend was associated with self-reported myopia (all P values < 0.001); in the junior high group, social jet lag was not associated with myopia (all P values > 0.05); in the senior high group, not getting up at a fixed time was related to self-reported myopia (P < 0.05).
Table 2
Comparison of self-reported myopia rates in children and adolescents with different sleep status stratified by grade.
Variable | Total | | Primary | | Junior high | | | Senior high |
Number of participants | Myopia cases | Myopia rate (%) | | Number of participants | Myopia cases | Myopia rate (%) | | Number of participants | Myopia cases | Myopia rate (%) | | | Number of participants | Myopia cases | Myopia rate (%) |
Night sleep duration | | | | | | | | | | | | | | | | |
༜7 h/d | 13,354 | 9,162 | 68.6 | | 1,336 | 491 | 36.8 | | 4,540 | 2,953 | 65.0 | | | 7,478 | 5,718 | 76.5 |
7–8 h/d | 7,862 | 3,395 | 43.2 | | 4,273 | 1,134 | 26.5 | | 2,671 | 1,605 | 60.1 | | | 918 | 656 | 71.5 |
8–9 h/d | 7,491 | 2,084 | 27.8 | | 6,510 | 3,431 | 23.3 | | 873 | 498 | 57.0 | | | 108 | 68 | 63.0 |
≥ 9 h/d | 1,481 | 385 | 26.0 | | 1,301 | 1,518 | 22.1 | | 148 | 81 | 54.7 | | | 32 | 16 | 50.0 |
χ2-trend | | 3695.82 | | | | 94.22 | | | | 32.32 | | | | | 26.42 | |
P value | | < 0.001 | | | | < 0.001 | | | | < 0.001 | | | | | < 0.001 | |
Fall asleep at a fixed time at night | | | | | | | | | | | | | | | | |
Yes | 19,585 | 9,164 | 46.8 | | 11,739 | 2,871 | 24.5 | | 6,888 | 4,281 | 62.2 | | | 6,888 | 5,200 | 62.4 |
No | 10,603 | 5,862 | 55.3 | | 1,681 | 560 | 33.3 | | 1,344 | 856 | 62.4 | | | 1,648 | 1,258 | 76.3 |
χ2 | | 198.58 | | | | 60.61 | | | | 1.14 | | | | | 0.51 | |
P value | | < 0.001 | | | | < 0.001 | | | | 0.287 | | | | | 0.475 | |
Get up at a fixed time in the morning | | | | | | | | | | | | | | | | |
Yes | 25,515 | 12,352 | 48.4 | | 9,773 | 2,263 | 23.2 | | 8,232 | 5,137 | 62.4 | | | 5,467 | 4,175 | 76.4 |
No | 4,673 | 2,674 | 57.2 | | 3,647 | 1,168 | 32.0 | | 4,345 | 2,726 | 62.7 | | | 3,069 | 2,283 | 74.4 |
χ2 | | 122.67 | | | | 109.82 | | | | 0.443 | | | | | 4.18 | |
P value | | < 0.001 | | | | < 0.001 | | | | 0.506 | | | | | 0.041 | |
Put off sleeping on weekends | | | | | | | | | | | | | | | | |
no | 6,263 | 2,945 | 47.0 | | 2,915 | 694 | 23.8 | | 1,767 | 1,070 | 60.6 | | | 1,581 | 1,181 | 74.7 |
< 1 h/d | 14,439 | 6,852 | 47.5 | | 7,121 | 1,752 | 24.6 | | 3,596 | 2,261 | 62.9 | | | 3,722 | 2,839 | 76.3 |
1–2 h/d | 5,868 | 3,043 | 51.9 | | 2,457 | 669 | 27.2 | | 1,603 | 1,000 | 62.4 | | | 1,808 | 1,374 | 76.0 |
≥ 2 h/d | 3,618 | 2,186 | 60.4 | | 927 | 316 | 34.1 | | 1,266 | 806 | 63.7 | | | 1,425 | 1,064 | 74.7 |
χ2-trend | | 181.06 | | | | 36.78 | | | | 2.27 | | | | | 0.033 | |
P value | | < 0.001 | | | | < 0.001 | | | | 0.132 | | | | | 0.856 | |
Put off getting up on weekends | | | | | | | | | | | | | | | | |
no | 5,610 | 2,400 | 42.8 | | 3,092 | 756 | 24.5 | | 1,501 | 885 | 59.0 | | | 1,017 | 759 | 74.6 |
< 1 h/d | 11,793 | 5,519 | 46.8 | | 5,918 | 1,454 | 24.6 | | 3,044 | 1,947 | 64.0 | | | 2,831 | 2,118 | 74.8 |
1–2 h/d | 6,881 | 3,507 | 51.0 | | 3,011 | 783 | 26.0 | | 1,767 | 1,095 | 62.0 | | | 2,103 | 1,629 | 77.5 |
≥ 2 h/d | 5,904 | 3,600 | 61.0 | | 1,399 | 438 | 31.3 | | 1,920 | 1,210 | 63.0 | | | 2,585 | 1,952 | 75.5 |
χ2-trend | | 424.31 | | | | 20.46 | | | | 2.20 | | | | | 1.03 | |
P value | | < 0.001 | | | | < 0.001 | | | | 0.138 | | | | | 0.311 | |
Table 3 and Fig. 1 showed the association between sleep status and the risk of self-reported myopia: Controlling of factors such as sex, age (years), outdoor activity, academic record, study burden, family economic level, father’s education, mother’s education, father myopia, mother myopia, the results of logistic analysis showed that the OR (95% CI) for myopia was 2.02 (1.87–2.19) in participants with night sleep duration < 7 h/d compared with students with night sleep duration 8–9 h/d; the ORs (95% CIs) for self-reported myopia were 1.14 (1.08–1.20) and 1.28 (1.19–1.37) in students who did not fall asleep at a fixed time at night and get up at a fixed time in the morning, respectively; the ORs (95% CIs) for self-reported myopia were 1.28 (1.17–1.41) and 1.23 (1.13–1.34) in students who put off sleeping ≥ 2 h/d and put off getting up ≥ 2 h/d on weekends, respectively.
Table 3
Multivariate logistic regression analysis of different sleep status and self-reported myopia in children and adolescents.
Variables | Model 1 | | Model 2 |
OR (95%CI) | P value | | Primary | | Junior high | | Senior high |
| OR (95%CI) | P value | | OR (95%CI) | P value | | OR (95%CI) | P value |
Night sleep duration | | | | | | | | | | | |
8–9 h/d | 1.00 | | | 1.00 | | | 1.00 | | | 1.00 | |
< 7 h/d | 2.02 (1.87–2.19) | < 0.001 | | 1.60 (1.41–1.83) | < 0.001 | | 1.18 (1.01–1.38) | 0.033 | | 1.63 (1.07–2.47) | 0.022 |
7–8 h/d | 1.30 (1.21–1.40) | < 0.001 | | 1.14 (1.04–1.25) | 0.005 | | 1.05 (0.90–1.23) | 0.573 | | 1.34 (0.86–2.07) | 0.208 |
≥ 9 h/d | 0.92 (0.80–1.05) | 0.202 | | 0.89 (0.77–1.03) | 0.126 | | 0.95 (0.67–1.36) | 0.786 | | 0.66 (0.29–1.49) | 0.313 |
Fall asleep at a fixed time at night | | | | | | | | | | | |
Yes | 1.00 | | | 1.00 | | | 1.00 | | | 1.00 | |
No | 1.14 (1.08–1.20) | < 0.001 | | 1.45 (1.33–1.58) | < 0.001 | | 0.95 (0.86–1.04) | 0.255 | | 0.93 (0.84–1.03) | 0.179 |
Get up at a fixed time int the morning | | | | | | | | | | | |
Yes | 1.00 | | | 1.00 | | | 1.00 | | | 1.00 | |
No | 1.28 (1.19–1.37) | < 0.001 | | 1.43 (1.27–1.60) | < 0.001 | | 1.13 (0.99–1.28) | 0.052 | | 1.10 (0.97–1.25) | 0.143 |
Put off sleeping on weekends | | | | | | | | | | | |
no | 1.00 | | | 1.00 | | | 1.00 | | | 1.00 | |
< 1 h/d | 1.04 (0.97–1.11) | 0.277 | | 1.07 (0.97–1.19) | 0.185 | | 1.09 (0.96–1.23) | 0.176 | | 1.04 (0.90–1.19) | 0.627 |
1–2 h/d | 1.09 (1.01–1.18) | 0.035 | | 1.17 (1.03–1.33) | 0.017 | | 1.09 (0.94–1.25) | 0.259 | | 1.02 (0.87–1.20) | 0.835 |
≥ 2 h/d | 1.28 (1.17–1.41) | < 0.001 | | 1.52 (1.29–1.80) | < 0.001 | | 1.23 (1.06–1.44) | 0.006 | | 1.01 (0.85–1.20) | 0.914 |
Put off getting up on weekends | | | | | | | | | | | |
no | 1.00 | | | 1.00 | | | 1.00 | | | 1.00 | |
< 1 h/d | 1.05 (0.98–1.13) | 0.181 | | 1.05 (0.94–1.16) | 0.412 | | 1.13 (0.99–1.28) | 0.071 | | 0.92 (0.78–1.10) | 0.362 |
1–2 h/d | 1.10 (1.02–1.19) | 0.017 | | 1.12 (0.99–1.27) | 0.057 | | 1.08 (0.89–1.18) | 0.748 | | 1.03 (0.86–1.23) | 0.780 |
≥ 2 h/d | 1.23 (1.13–1.34) | < 0.001 | | 1.36 (1.17–1.57) | < 0.001 | | 1.12 (0.97–1.29) | 0.129 | | 0.95 (0.80–1.13) | 0.539 |
Note. Model 1: adjusted for sex, age (years), outdoor activity, academic record, study burden, family economic level, father’s education, mother’s education, father myopia, mother myopia. |
Model 2: stratified by grade, adjusted for sex, age (years), outdoor activity, academic record, study burden, family economic level, father’s education, mother’s education, father myopia, mother myopia. |
After stratification by grade (Table 3, Fig. 2–4), for night sleep duration < 7h/d, the ORs (95%CIs) were respectively 1.60 (1.41–1.83), 1.18 (1.01–1.38) and 1.63 (1.07–2.47) among primary, junior and senior high students; in primary group, not falling asleep at night and not getting up at a fixed time in the morning, putting off sleeping ≥ 2h/d and getting up ≥ 2h/d on weekends had the most obvious effect among primary groups, and the ORs (95% CIs) were respectively 1.45 (1.33–1.58), 1.43 (1.27–1.60), and 1.52 (1.29–1.80), which indicated that social jet lag was significantly associated with myopia among primary students. In junior high group, putting off sleeping was significantly associated with myopia with ORs (95% CIs) 1.23 (1.06–1.44), while not falling asleep at a fixed time at night, not getting up at a fixed time in the morning and and getting up ≥ 2h/d on weekends were not risk factors. In senior high group, social jet lag was not associated with self-reported myopia (all P values > 0.05)