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Public health
Original research
Prevalence and related factors of children myopia in Pudong New Area, Shanghai: a cross-sectional study
  1. Peng Cheng1,
  2. Xiaohua Zhang1,2,
  3. Wei Zhou1,
  4. Jiawei Xu1,
  5. Fangrong Chen1,
  6. Dan Qian1,
  7. Bin Cao1
  1. 1Eye and Dental Diseases Prevention & Treatment Center of Pudong New Area, Shanghai, China
  2. 2School of Public Health, Fudan University, Shanghai, China
  1. Correspondence to Professor Bin Cao; pdyyfs_cb{at}126.com

Abstract

Objectives This study aimed to assess the prevalence and related factors of myopia among school-aged children after COVID-19 pandemic.

Design Cross-sectional study.

Setting Pudong New Area, Shanghai.

Participants 1722 children aged 7–9 randomly selected from 8 primary schools were screened from 1 February 2023 to 30 April 2023.

Main outcome measures Children’s height, weight and eye parameters were examined. Myopia was defined as a cycloplegic spherical equivalent ≤−0.50 dioptres in either eye. A vision-related behaviour questionnaire was applied to investigate the associations between myopia and its risk factors.

Results Of the 1722 individuals enrolled, 25.6% (456) had myopia. After adjusting other characteristics, the following factors were associated with an increased rate of myopia: age (9 years vs 7 years, adjusted OR (AOR) 1.84, 95% CI 1.18 to 2.85, p=0.007), parental myopia status (both myopia vs none, AOR 5.66, 95% CI 3.71 to 8.63, p<0.001; one myopia vs none, AOR 2.92, 95% CI 1.93 to 4.42, p<0.001), reading books too close (yes vs no, AOR 1.58, 95% CI 1.20 to 2.08, p=0.001), writing with a tilted head (yes vs no, AOR 1.37, 95% CI 1.05 to 1.77, p=0.019), sleep patterns (early to bed late to rise vs early to bed early to rise, AOR 1.52, 95% CI 1.02 to 2.26, p=0.039). By contrast, a higher monthly household income and the habit of reading while lying down were associated with lower risk of myopia.

Conclusions The prevalence of myopia is of concern among young school-aged children after COVID-19. Correcting eye use behaviour and improving sleep habits may reduce myopia. Also, gender differences should be considered in prevention strategies for children’s myopia.

  • COVID-19
  • schools
  • risk factors
  • public health
  • community child health

Data availability statement

Data are available on reasonable request.

http://creativecommons.org/licenses/by-nc/4.0/

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

https://doi.org/10.1136/bmjopen-2023-079330

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    STRENGTHS AND LIMITATIONS OF THIS STUDY

    • This study assessed the prevalence of myopia in young school-aged children after COVID-19 pandemic with cycloplegic refraction.

    • In addition to outdoor activity and near screen time, this study investigated the associations of eye habits and sleep on children’s myopia.

    • Gender stratification was used to conduct a thorough evaluation of the risk factors of myopia in school-aged children.

    • The cross-sectional study design limits our ability to determine a causal relationship between myopia and its risk factors, and questionnaire surveys has recall bias.

    Introduction

    Myopia is a growing global health issue,1 and it is projected that by 2050, 50% of the total population will be affected.2 Myopia is more prevalent in East Asian countries than in Europe and America, with rates as high as 90% among young people in China.1 Myopia does not occur and develop suddenly, so it is crucial to prioritise the eye health of school-aged children. In China, the myopia rate for fourth grade primary school students was 37.1% in 2015, according to a national survey.3 In Taiwan, a research report stated that the myopia rate for second grade primary school students was 36.4% in 2013.4 In Guangzhou, a study found that the myopia rate for first to ninth grade students ranged from 0.2% to 68.4%, with the greatest difference between second and third grade (25.5%).5

    In order to prevent and control myopia, many researchers have been making efforts. Watching near screen and outdoor activities played a role in myopia for school-aged children.6 7 However, the sudden outbreak of COVID-19 in December 2019 increased their near screen time (online learning), and limited their outdoor activities (home quarantine). As per Zhou et al, myopia rates among primary school students in grades 2–4 increased during COVID-19 pandemic, with rates of 19.1%, 33.0% and 49.5% in 2021, respectively.8

    Myopia in young pupils has increased rapidly. With COVID-19 entering the normal prevention and control stage, teaching order and outdoor activities have resumed. This study aims to understand the prevalence of myopia in school-aged children after COVID-19 pandemic and to assess related risk factors, particularly the impact of eye habits and sleep on myopia.

    Methods

    Study design and population

    From 1 February 2023 to 30 April 2023, students of grades 2–3 enrolled in this cross-sectional study were randomly selected from 8 schools in Pudong New Area (covering an area of 1210 km2 and with a permanent population of 5.77 million), Shanghai (figure 1). The schools were selected through random number method and 200 students were chosen through cluster sampling. If there were not enough students, new classes would be added. Students aged over 7–9 years or refusing cycloplegia (including unsuitable for cycloplegia due to other diseases) were excluded. School-aged children were engaged in conduct and dissemination plan of this research. These children and their parents (or legal guardians) were provided with information about the nature and extent of their involvement in the research and agreed to participate in. The final results will be shared with participants through the internet or smartphone.

    Figure 1
    Figure 1

    Study population selection.

    Patient and public involvement

    No patient involved.

    Procedures

    The on-site examination was completed in the school, including height (0.1 cm accuracy; C808, Carefully, China), weight (0.01 kg accuracy; Xiaomi Scale, MIUI, China), eye axis (IOL Master 500, Carl Zeiss Meditec AG, Germany), intraocular pressure (NT-510, Nidek, Japan), Slit lamp examination (YZ-5E, 66 Vision Tech, China), refraction (KR-800, Topcon, Japan). For cycloplegic refraction, we referred to the method of He et al.9 Two drops of 1% cyclopentolate hydrochloride (Cyclogyl, Alcon, Belgium), with a 5 min interval, were used to induce cycloplegia (if insufficient then add another drop). Refraction assessment was performed after the pupils were >6 mm and without light reflex. Our data management system was directly linked to the refractive examination instrument, reducing recording errors. The inspectors and ophthalmologists involved in the on-site inspection had received systematic training and certification before entering the school.

    Risk factor assessment

    A vision-related behaviour questionnaire was applied to investigate the associations between myopia and its risk factors retrospectively (see online supplemental files 1 and 2 for details about the complete questionnaire). The self-administered paper questionnaires were taken home by students and completed under the guidance of their parents. Children’s information mainly includes: name, age, gender, grade, preterm birth or not (yes/no), outdoor activity time (hours per day; weekday and weekend), near screen time (ie, time for mobiles, tablets, televisions and computers; hours per day; weekday and weekend), eye habits (ie, reading books too close (yes/no), watching a screen too close (yes/no), writing with a tilted head (yes/no) and reading while lying down (yes/no)), sleep status (referred to the Pittsburgh Sleep Quality Index10) for the past month (bedtime, wake-up time and sleep duration). Other information includes: parental age, parental education (less than high school/high or secondary vocational school/college or junior college/graduate or above), monthly family income (<¥10 000/¥10 001–¥20 000/¥20 001–¥50 000/>¥50 000), parental myopia status (none/one myopia/both myopia).

    Definitions

    The spherical equivalent (SE) of the refractive error was calculated by adding half of the cylindrical value to the spherical value. Myopia was defined as an SE≤−0.50 dioptres (D) in either eye and was categorised as low (−0.50 D≥SE>−3.00 D), moderate (−3.00 D≥SE>−6.00 D) or high (SE≤−6.00 D) based on the degree of refractive error. Emmetropia was defined as an SE within±0.50 D, while hyperopia was ≥+0.5 D.11 Body mass index (BMI) was determined using the formula weight (kg) divided by height squared (m2). BMI was categorised as overweight (P85≤BMI< P95), obese (BMI>P95) or normal weight (BMI<P85).12 Parental education level refers to the highest level of education attained by either parent. Students were divided into two groups based on the median of monthly household income (yuan), bedtime, wake-up time and sleep duration (<P50,≥P50). According to the median division of bedtime and wake-up time, we categorise students’ sleep into four patterns (early to bed early to rise (EE), late to bed early to rise (LE), early to bed late to rise (EL) and late to be late to rise (LL)).13 The analysis only included cases who completed questionnaire surveys and on-site inspections.

    Statistical analysis

    EpiData software V.3.1 (2008-01-27) was employed for questionnaire data dual entry and validation. All statistical analyses were performed using R software V.4.3.1 (2023-06-16). We calculated the percentages of students for the categorical data, expressed continuous data as median and IQR, and assessed the differences between groups using Wilcoxon and χ2 tests. Multivariate logistic regression analysis was performed to estimate the ORs and 95% CIs of potential risk factors with myopia status (myopia/no myopia). Values of p<0.05 were considered statistically significant.

    Results

    Information was available for 1722 primary students. Table 1 shows the details of ocular parameters in different myopia status. Of these enrolled, 25.6% had myopia and 3.1% had moderate myopia. Violin box plot shows the distribution of ocular parameters according to myopia status and gender (figure 2). Compared with female students, male students had a longer axial length (AL) (p<0.001) and a higher AL/corneal radius (CR) ratio (p<0.001). In the subgroup analysis for non-myopia students, girls’ SE was higher than that of boys.

    Figure 2
    Figure 2

    Distribution of ocular parameters by myopia status and gender. (A) Spherical equivalent. (B) Axial length. (C) The ratio of axial length/corneal radius. The red dashed line marks the median level of all participants. AL, axial length; CR, corneal radius; D, dioptres; SE, spherical equivalent.

    View this table:
    Table 1

    Ocular parameters in different myopia status

    The myopes were, by comparison, older and more common among the girls (table 2). Myopes’ parents had lower educational levels and higher myopia rates of myopia than non-myopes’ parents. Myopes were more likely to read books too close, write with tilted heads and bad sleep habits than non-myopes. More non-myopes enjoyed reading while lying down, but this difference did not reach statistical significance in the univariate analysis.

    View this table:
    Table 2

    Characteristics of study participants

    Considering the differences in ocular parameters and myopia prevalence rates found between boys and girls, we performed multivariate analysis to test the associations between the risk factors and myopia status (myopia/no myopia) in different models (table 3). Students with myopic parents had higher myopia risk compared with those without myopic parents, and students with both parents having myopia had almost double the risk compared with those with one myopic parent. In model 2, male myopes were more likely to watch screen too close (yes vs no; adjusted OR (AOR) 1.67, p=0.010), write with a tilted head (yes vs no; AOR 1.69, p=0.006) and have bad sleep patterns (LL vs EE; AOR 1.92, p=0.020). For girls, older age (9 years vs 7 years; AOR 2.18, p=0.017) and near-distance reading (yes vs no; AOR 2.45, p<0.001) contributed to higher myopia risk, whereas a higher monthly family income reduced the risk. The habit of reading while lying down (yes vs no; AOR 0.68, p=0.037) and EL sleep pattern (EL vs EE; AOR 1.52, p=0.039) had an impact on myopia in the overall analysis (model 1), but their impact was not significant in the subgroup analysis.

    View this table:
    Table 3

    Related factors for myopia

    Discussion

    After COVID-19 pandemic, the prevalence of myopia in primary school students aged 7–9 in Pudong New Area was 25.6% (7 years: 24.6%; 8 years: 25.7%; 9 years: 33.2%) based on cycloplegic refraction. This was higher than the myopia rates found in a cross-sectional study in Nantong, where children aged 7–9 had a myopia rate ranging from 10.1% to 23.7% without cycloplegic refraction in 2022.14 The myopia rate in Shanghai 10 years ago differs from what was found in our study. Among 7-year-old students, the rate is 14.3%, while for 8-year-old students, it is 30.8%, and for 9-year-old students, it is 41.4%.15 In addition to time for outdoor activity and near screen, student age, monthly household income, parental myopia status, child eye habits and sleep status were associated with an increased risk of myopia. In particular, gender differences in myopia risk factors were observed among school children aged 7–9 years old, and the habit of reading while lying down was associated with a lower myopia risk.

    In the univariate analysis, we found that female students had a higher myopia rate than male students (28.9% vs 24.3%), but this difference was not statistically significant in the multivariate logistic regression model. Female students had a higher risk of myopia than male students, as shown by a study on second-grade primary school children in Taiwan, and this was confirmed through both univariate (OR 1.22, p<0.001) and multivariate (OR 1.24, p<0.001) analyses.4 We also found that male students had a longer AL (p<0.001) and a higher AL/CR ratio (p<0.001) than female students, but their SE levels showed no significant difference. Unlike us, Zhou et al found that the SE level of female students was consistently lower than that of male students from 2019 to 2022, and SE decreased with grade for primary and junior school students.8 This seems to suggest that if we do not take action, the overall visual condition of girls will worsen, despite finding that non-myopic girls had higher SE levels than non-myopic boys in subgroup analysis. As for BMI, Theophanous et al16 did not find any impact on myopia,17 but two studies targeting young men found an association between BMI and myopia.17 18 Preterm birth increased the risk of congenital myopia,19 but we found no association between preterm birth and myopia.

    The association between parental characteristics and myopia has been described among children in different studies.16 20 21 Our data support the notion that myopia has a strong genetic component, as evidenced by previous researches. A cohort study on preschool children found that parental myopia increased the risk of myopia in preschool children from different countries.20 Additionally, parental myopia was associated with higher AL/CR ratio and more myopic refractive error, even in children without myopia.20 Hsu et al found that second grade primary school students with one nearsighted parent had an increased risk of myopia, while those with two nearsighted parents had a higher risk.4 The relationship between parental education level and children’s myopia status was unstable. A correlation was found in The Hong Kong Children Eye Study, suggesting that higher parental education levels were associated with a higher risk of myopia in children. However, this association disappeared after accounting for other variables.21 Hsu et al found an association between maternal education level and myopia, while Saxena et al found the association became insignificant after adjusting for other variables.4 22 The association between family income and children’s myopia status has been less mentioned in most studies. Our study found that higher monthly household income was associated with a lower risk of myopia in children, particularly among girls.

    As per Rudnicka et al,23 the increase in myopia prevalence in Asians suggests genetics is not the dominant cause, studies on preventing and controlling myopia are focusing on environmental and behavioural factors, especially in outdoor activities and near screen. In our study, we observed insignificant associations between time for outdoor activities or near screen and myopia. Although associations between outdoor activity time and near screen time with myopia had been found in some cross-sectional studies, this association was not robust and became insignificant in the multivariate regression models.4 21 A school-based cluster randomised trial suggested that increased outdoor time was associated with a reduced risk of myopia onset and myopic shifts, with the protective effect being influenced by the duration of exposure and light intensity.9 The related leading hypothesis is that light triggers dopamine release in the retina, which prevents eye elongation during development. Close work might still make some effect, but exposure to bright light is what mattered most.1 In addition, exploring alternative methods to improve children’s visual acuity may be necessary due to challenges in implementing effective outdoor activities for myopia prevention.

    Children’s eye habits accompany their growth, and the impact on their vision cannot be ignored. Our data indicated that reading books too close, watching a screen too close and writing with a tilted head were associated with myopia in school-aged children, with a gender difference in the strength of this association. Close reading may contribute to myopia for girls, while watching a screen too close and writing with a slanted head may increase myopia risk for boys. Higher myopia was connected with shorter reading distance in girls, according to a Finland’s longitudinal study.24 In 2014, a survey conducted in Guangzhou with students (ranging from grades 1–9) by Guo et al, they found that close reading was correlated with a higher risk of myopia for all students. However, they only found a higher risk of myopia from close television viewing among female students.5 We believe that the emergence of such differences is reasonable. The time gap between the two studies is approximately 10 years and China’s socioeconomic development has led to increased access to mobile phones, tablets and computers. Televisions may no longer be the primary medium for children’s electronic screen usage. Even, providing children with mobile phones can temporarily reduce their frequent interruptions to their parents. We had not found any relevant descriptions in other studies regarding writing with a slanted head. Surprisingly, we also found that reading while lying down may be relevant to a lower risk of myopia among these children. So, we reviewed previous studies on the association between lying down reading and myopia risk. Zhuang et al suggest that reading while lying down was related to myopia,25 but the essence of ‘reading’ here is ‘watching screens’; Shi et al’s study defined poor reading pose as reading while lying down, walking or in a moving car, and they found a association between it and myopia.26 Finland’s study provided the closest definition to reading while lying down in our study. They found that sitting posture during reading associated with higher myopic progression, while reading face up associated with lower progression.24 Here, based on our results, we propose a bold idea—lying down and training, and in a right way (ie, appropriate distance and posture, limited time and rotating eyeballs)—may be able to block eye elongation during development.

    In our study, myopia risk was higher in the EL sleep pattern group compared with the EE sleep pattern group for all students (AOR 1.52, p=0.039). However, the LL sleep pattern group only had a higher myopia prevalence than the EE sleep pattern group among boys (AOR 1.92, p=0.020; p=0.075 in total (close to 0.05)). We did not observe a significant association between sleep duration and myopia. Recently, a systematic review found that there is still much to learn about the relationship between children myopia and sleep (including duration, quality, timing and efficiency). More accurate evaluation methods are needed.27 Nevertheless, our data suggest that sleep patterns have a more significant impact on myopia in boys compared with girls.

    Our study has limitations. The cross-sectional study design limits our ability to determine a causal relationship between myopia and its influencing factors. Although we evaluated students’ myopia by using cycloplegic refraction data, the assessment of children’s outdoor activities, close range videos, eye habits and sleep status relied on children and their parents. Also, cross-sectional design carries a risk of confounding bias and questionnaire surveys has recall bias. Correlation was found between lying down reading and lower myopia risk among school-going children aged 7–9 years, but details of reading while lying down was not specified, and with no restrictions on reading distance or time. More research is needed to determine the relationship between near work activities, such as lying reading and myopia in school-aged children of various age groups.

    In conclusion, this study evaluated myopia prevalence in school-aged children after COVID-19 pandemic. Correcting eye use behaviour and improving sleep habits may reduce myopia. And gender differences should be considered in prevention strategies for children’s myopia.

    Data availability statement

    Data are available on reasonable request.

    Ethics statements

    Patient consent for publication

    Ethics approval

    This study involves human participants and this study was approved by the Medical Ethics Committee of Eye and Dental Diseases Prevention and Treatment Center of Pudong New Area, Shanghai (No. PDYYF-LLSC-202101-SP) and adhered to the tenets of the Declaration of Helsinki. Participants and their parents signed written informed consent forms before conducting questionnaire surveys and on-site examinations. Participants gave informed consent to participate in the study before taking part.

    Acknowledgments

    The authors would like to express deepest gratitude to all the researchers and schoolchildren in this study.

    References

    1. ↵
      1. Dolgin E
      . The myopia boom. Nature 2015;519:276–8. doi:10.1038/519276a
      OpenUrlCrossRefPubMed
    2. ↵
      1. Holden BA,
      2. Fricke TR,
      3. Wilson DA, et al
      . Global prevalence of myopia and high myopia and temporal trends from 2000 through 2050. Ophthalmology 2016;123:1036–42. doi:10.1016/j.ophtha.2016.01.006
      OpenUrlCrossRefPubMed
    3. ↵
      1. Wang S,
      2. Hao X,
      3. Ma X, et al
      . Associations between poor vision, vision-related behaviors and mathematics achievement in Chinese students from the CNAEQ-PEH 2015. IJERPH 2020;17:8561. doi:10.3390/ijerph17228561
      OpenUrl
    4. ↵
      1. Hsu C-C,
      2. Huang N,
      3. Lin P-Y, et al
      . Prevalence and risk factors for myopia in second-grade primary school children in Taipei: a population-based study. J Chin Med Assoc 2016;79:625–32. doi:10.1016/j.jcma.2016.02.011
      OpenUrlPubMed
    5. ↵
      1. Guo L,
      2. Yang J,
      3. Mai J, et al
      . Prevalence and associated factors of myopia among primary and middle school-aged students: a school-based study in Guangzhou. Eye (Lond) 2016;30:796–804. doi:10.1038/eye.2016.39
      OpenUrl
    6. ↵
      1. Wang W,
      2. Zhu L,
      3. Zheng S, et al
      . Survey on the progression of myopia in children and adolescents in Chongqing during COVID-19 pandemic. Front Public Health 2021;9:646770. doi:10.3389/fpubh.2021.646770
      OpenUrl
    7. ↵
      1. Jones LA,
      2. Sinnott LT,
      3. Mutti DO, et al
      . Parental history of myopia, sports and outdoor activities, and future myopia. Invest Ophthalmol Vis Sci 2007;48:3524–32. doi:10.1167/iovs.06-1118
      OpenUrlAbstract/FREE Full Text
    8. ↵
      1. Zhou W,
      2. Li Q,
      3. Chen H, et al
      . Trends of myopia development among primary and junior school students in the post-COVID-19 epidemic period. Front Public Health 2022;10:970751. doi:10.3389/fpubh.2022.970751
    9. ↵
      1. He X,
      2. Sankaridurg P,
      3. Wang J, et al
      . Time outdoors in reducing myopia: a school-based cluster randomized trial with objective monitoring of outdoor time and light intensity. Ophthalmology 2022;129:1245–54. doi:10.1016/j.ophtha.2022.06.024
      OpenUrl
    10. ↵
      1. Buysse DJ,
      2. Reynolds CF,
      3. Monk TH, et al
      . The Pittsburgh sleep quality index: a new instrument for psychiatric practice and research. Psychiatry Res 1989;28:193–213. doi:10.1016/0165-1781(89)90047-4
      OpenUrlCrossRefPubMedWeb of Science
    11. ↵
      1. Flitcroft DI,
      2. He M,
      3. Jonas JB, et al
      . IMI - defining and classifying myopia: a proposed set of standards for clinical and epidemiologic studies. Invest Ophthalmol Vis Sci 2019;60:M20–30. doi:10.1167/iovs.18-25957
      OpenUrlCrossRefPubMed
    12. ↵
      1. Styne DM,
      2. Arslanian SA,
      3. Connor EL, et al
      . Pediatric obesity-assessment, treatment, and prevention: an endocrine society clinical practice guideline J Clin Endocrinol Metab 2017;102:2123–4. doi:10.1210/jc.2017-00561
      OpenUrl
    13. ↵
      1. Zhao J,
      2. Xu J,
      3. He Y, et al
      . Children and adolescents' sleep patterns and their associations with mental health during the COVID-19 pandemic in Shanghai, China. J Affect Disord 2022;301:337–44. doi:10.1016/j.jad.2021.12.123
      OpenUrl
    14. ↵
      1. Zhou Y,
      2. Zhang XF,
      3. Chen XJ, et al
      . Prevalence of anisometropia and influencing factors among school-age children in Nantong, China: a cross-sectional study. Front Public Health 2023;11:1190285. doi:10.3389/fpubh.2023.1190285
      OpenUrl
    15. ↵
      1. Ma Y,
      2. Qu X,
      3. Zhu X, et al
      . Age-specific prevalence of visual impairment and refractive error in children aged 3-10 years in Shanghai, China. Invest Ophthalmol Vis Sci 2016;57:6188–96. doi:10.1167/iovs.16-20243
      OpenUrlCrossRefPubMed
    16. ↵
      1. Theophanous C,
      2. Modjtahedi BS,
      3. Batech M, et al
      . Myopia prevalence and risk factors in children. Clin Ophthalmol 2018;12:1581–7. doi:10.2147/OPTH.S164641
      OpenUrl
    17. ↵
      1. Lee DC,
      2. Lee SY,
      3. Kim YC
      . An epidemiological study of the risk factors associated with myopia in young adult men in Korea. Sci Rep 2018;8:511. doi:10.1038/s41598-017-18926-2
    18. ↵
      1. Bez D,
      2. Megreli J,
      3. Bez M, et al
      . Association between type of educational system and prevalence and severity of myopia among male adolescents in Israel. JAMA Ophthalmol 2019;137:887–93. doi:10.1001/jamaophthalmol.2019.1415
      OpenUrl
    19. ↵
      1. Semeraro F,
      2. Forbice E,
      3. Nascimbeni G, et al
      . Ocular refraction at birth and its development during the first year of life in a large cohort of babies in a single center in northern Italy. Front Pediatr 2019;7:539. doi:10.3389/fped.2019.00539
    20. ↵
      1. Jiang X,
      2. Tarczy-Hornoch K,
      3. Cotter SA, et al
      . Association of parental myopia with higher risk of myopia among multiethnic children before school age. JAMA Ophthalmol 2020;138:501–9. doi:10.1001/jamaophthalmol.2020.0412
      OpenUrl
    21. ↵
      1. Tang SM,
      2. Kam KW,
      3. French AN, et al
      . Independent influence of parental myopia on childhood myopia in a dose-related manner in 2,055 trios: the Hong Kong children eye study. Am J Ophthalmol 2020;218:199–207. doi:10.1016/j.ajo.2020.05.026
      OpenUrl
    22. ↵
      1. Saxena R,
      2. Gupta V,
      3. Prasad P, et al
      . Prevalence of myopia and its risk factors in rural school children in North India: the North India myopia rural study (NIM-R study). Eye (Lond) 2022;36:2000–5. doi:10.1038/s41433-021-01797-3
      OpenUrl
    23. ↵
      1. Rudnicka AR,
      2. Kapetanakis VV,
      3. Wathern AK, et al
      . Global variations and time trends in the prevalence of childhood myopia, a systematic review and quantitative meta-analysis: implications for aetiology and early prevention. Br J Ophthalmol 2016;100:882–90. doi:10.1136/bjophthalmol-2015-307724
      OpenUrlAbstract/FREE Full Text
    24. ↵
      1. Pärssinen O,
      2. Kauppinen M
      . Associations of reading posture, gaze angle and reading distance with myopia and myopic progression. Acta Ophthalmol 2016;94:775–9. doi:10.1111/aos.13148
      OpenUrl
    25. ↵
      1. Zhuang M,
      2. Xie H,
      3. Zhang Y, et al
      . Prevalence and influence factors for myopia and high myopia in schoolchildren in Shandong, China. Cent Eur J Public Health 2022;30:190–5. doi:10.21101/cejph.a7158
      OpenUrl
    26. ↵
      1. Shi H,
      2. Fu J,
      3. Liu X, et al
      . Influence of the interaction between parental myopia and poor eye habits when reading and writing and poor reading posture on prevalence of myopia in school students in Urumqi, China. BMC Ophthalmol 2021;21:299. doi:10.1186/s12886-021-02058-3
    27. ↵
      1. Liu XN,
      2. Naduvilath TJ,
      3. Sankaridurg PR
      . Myopia and sleep in children - a systematic review. Sleep 2023;46:zsad162. doi:10.1093/sleep/zsad162

    Supplementary materials

    • Supplementary Data

      This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.

    Footnotes

    • PC and XZ are joint first authors.

    • Contributors PC: concept and editing of the manuscript, conduction of the study, data collection, data analysis, and preparation of manuscript. XZ: funding acquisition, concept and editing of the manuscript, conduction of the study and data collection, and revision of the article. WZ, FC and DQ: conduction of the study and data collection. JX: data analysis, conduction of the study and data collection. BC: funding acquisition, concept and editing of the manuscript, supervision and revision of the article. BC is responsible for the overall content as the guarantor.

    • Funding This work was supported by Shanghai Municipal Health Commission (Grant No. ZY(2021-2023)-0105), Shanghai Pudong New Area Science and Technology and Economic Commission (Grant No. PKJ2021-Y96), Shanghai Pudong New Area Health Commission (Grant No. PWYgts2021-03 and PDZY-2021-0503), Shanghai Eye Disease Prevention and Treatment Center (HYXG-QJ01).

    • Competing interests None declared.

    • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

    • Provenance and peer review Not commissioned; externally peer reviewed.

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