Associations Between Reading and Writing Posture and Myopia Among School Students in Ningbo, China

doi:10.21203/rs.3.rs-277237/v1

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Associations Between Reading and Writing Posture and Myopia Among School Students in Ningbo, China

https://doi.org/10.21203/rs.3.rs-277237/v1

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Purpose: We conducted this study to examine the prevalence of myopia among school students in Ningbo, and to explore the associations between reading and writing posture and myopia.

Methods: A population-based and cross-sectional investigation was performed and 3256 school students aged 8 to 19 years old were recruited. Each enrolled subject underwent uncorrected distance visual acuity (UDVA) assessment using a standard logarithmic visual acuity E chart and non-cycloplegic autorefraction examination. Self-administered questionnaires were used to investigate myopia-related reading and writing posture and behavior habits.

Results: Myopia prevalence of primary school students, middle school students and high school students were 61.49%, 81.43% and 89.72%, respectively. In the associations between reading and writing posture and myopia, we identified keeping the distance between the eyes and the book could be the protective factor in female students, and in both primary school students and middle school students.

Conclusions: Keeping appropriate distance between the eyes and the book may be good for myopia prevention and control. We hope this work will bring educational and public health benefits to form appropriate reading and writing posture.

Ophthalmology

reading and writing posture

myopia

school students

keep distance

In recent decades, myopia in children and adolescents has been an important public health problem focused by the public [1]. In addition to genetic factors [2], environmental factors and habits and customs also have been proved to play an important role in the occurrence and development of children and adolescents' myopia, such as higher educational attainment and school achievement [3], greater amounts of near work [4], body stature [5], degree of urbanization [6], level of physical activity [7], level of outdoor activity [8], etc. At present, to study and control of environmental factors is the focus of myopia prevention. Among them, reading and writing posture related near vision behavior is one of the focuses of intervention [9].

To supervise and correct children's bad writing posture at any time, there is“one Chi, one fist and one Cun”principle in China (Chi and Cun are units of measurement in ancient China, one Chi = 33 cm, one Cun = 3.3 cm), that is, the distance between the eyes and the book should be about one Chi, the distance between the chest and the desk should be about one fist, and the distance between the fingers holding the pen and the tip of the pen should be about one Cun.

In China, almost all the criteria for reading and writing posture are based on the "three ones"principle. Some studies have further refined and supplemented the above criteria, and a few studies have adopted one of them alone. The distance between eyes and books is more commonly used, and the judgment standard is usually 30-33cm. Other researches related standards mainly include reading and writing distance, short-distance reading time, whether the body is sitting upright, whether there is forward or backward skew, etc.

We conducted this study to examine the prevalence of myopia among school students in Ningbo, and to explore the associations between reading and writing posture and myopia. We hope this work will bring educational and public health benefits to form appropriate reading and writing posture.

Study population

A population-based and cross-sectional investigation was performed to study the associations between reading and writing posture and myopia in Ningbo, Zhejiang. A total of 3256 school students aged 8 to 19 years old were recruited in our study, including 1088 primary school students, 1088 middle school students and 1080 high school students. Participants were selected by using a complex, stratified, multistage sample design.

Informed consent was obtained from all participants. The study was approved by the ethics committee of Ningbo Municipal Center for Disease Control and Prevention and followed the tenets of the Declaration of Helsinki.

Visual acuity measurement

Each enrolled subject underwent uncorrected distance visual acuity (UDVA) assessment using a standard logarithmic visual acuity E chart and non-cycloplegic autorefraction examination. Myopia was defined as UDVA < 5.0 and spherical equivalent (SE) < -0.50D.

Questionnaire investigation

Self-administered questionnaires were used, including students' basic information, myopia-related reading and writing posture and behavior habits. After the unified training, the investigators sent questionnaires to the school and asked the students to fill in, and the teachers would take them back. After collecting and reviewing the questionnaires, for incomplete and illogical questionnaires, investigators will check and contact the person who responded to explain it and fill in the questionnaire again.

Statistical analysis

The survey data were entered into EpiData 3.1 database. After logical check and data check, statistical analysis was performed using SPSS 20.0 software. Participants' characteristics were described using means and standard errors for continuous variables, and numbers and percentages for categorical variables. Logistic regression analysis was used to determine the associations between reading and writing posture and myopia. P< 0.05 was considered to be statistically significant.

The main characteristics of study participants were reported in Table 1. Of the 3256 school students, 33.42% is primary school students, 33.42% is middle school students and 33.17% is high school students. The average ages of three groups were 10.66, 13.59 and 16.59 years old, respectively. The proportions of male students were 53.77%, 50.37% and 46.20%, respectively. The situation of reading and writing posture was shown in Table 1 as well.

Table 1

Characteristics of all subjects included in the study.
Characteristics	Primary School (N = 1088)	Middle School (N = 1088)	High School (N = 1080)
Age	10.66 ± 0.86	13.59 ± 0.92	16.59 ± 0.89
Gender (M / F)	585 / 503	548 / 540	499 / 581
Myopia prevalence	61.49% (669 / 1088)	81.43% (886 / 1088)	89.72% (969 / 1080)
Male	58.63% (343 / 585)	78.28% (429 / 548)	87.17% (435 / 499)
Female	64.81% (326 / 503)	84.63% (457 / 540)	91.91% (534 / 581)
When you're reading and writing
The chest is more than one fist from the edge of the table
Never/ Sometimes/ Usually/ Always	135/ 340/ 321/ 290	78/ 408/ 322/ 279	92/ 434/ 330/ 218
The eyes are more than one Chi away from the book
Never/ Sometimes/ Usually/ Always	132/ 373/ 278/ 300	92/ 467/ 294/ 228	114/ 534/ 309/ 118
The finger is about one Cun away from the tip of the nose
Never/ Sometimes/ Usually/ Always	162/ 218/ 227/ 473	142/ 287/ 267/ 386	174/ 331/ 261/ 306
Does your teacher remind you that your reading and writing posture is not correct?
Never/ Sometimes/ Usually/ Always	181/ 302/ 227/ 372	191/ 419/ 231/ 243	357/ 488/ 158/ 72
Do your parents remind you that your reading and writing posture is not correct?
Never/ Sometimes/ Usually/ Always	91/ 272/ 253/ 467	97/ 274/ 326/ 387	140/ 419/ 357/ 159

Myopia prevalence of primary school students was 61.49%, 58.63% for male students and 64.81% for female students. Myopia prevalence of middle school students was 81.43%, 78.28% for male students and 84.63% for female students. Myopia prevalence of high school students was 89.72%, 87.17% for male students and 91.91% for female students (Fig. 1).

In the associations between reading and writing posture and myopia, we applied logistic regression analysis in different gender and different school types. As shown in Table 2, after adjusting for age and grade, the eyes are more than one Chi away from the book was identified as a protective factor in female students. And the more they choose to keep eyes are more than one Chi away from the book, the lower risk they will get myopic. Compared with the female students who choose "never" for "the eyes are more than one Chi away from the book", the ORs and 95% CIs for subjects who choose "sometimes", "usually", "always" were 0.522 (0.280, 0.974), 0.492 (0.253, 0.956) and 0.309 (0.150, 0.635), respectively. And in male students, the finger is about one Cun away from the tip of the nose turned out to be a protective factor as well. Compared with the male students who choose "never" for "the finger is about one Cun away from the tip of the nose", the OR and 95% CI for subjects who choose "sometimes" were 0.613 (0.390, 0.962). However, the chest is more than one fist from the edge of the table was a risk factor in female students for myopia (Usually: 1.894 (1.027, 3.494), Always: 2.005 (1.036, 3.882)). And in both male and female students, the more parents remind their reading and writing postures, they are more tend to be myopic.

Table 2

Logistic regression of myopia-related factors by gender.
Items	Male		Female
Items	OR (95% CI)	P value	OR (95% CI)	P value
Age	1.209 (1.056, 1.383)	0.006	1.267 (1.087, 1.477)	0.002
Grade	1.319 (0.868, 2.007)	0.195	1.243 (0.770, 2.006)	0.373
The chest is more than one fist from the edge of the table
Never	Reference
Sometimes	1.271 (0.781, 2.069)	0.334	1.301 (0.729, 2.324)	0.373
Usually	1.273 (0.760, 2.131)	0.359	1.894 (1.027, 3.494)	0.041
Always	1.157 (0.672, 1.994)	0.598	2.005 (1.036, 3.882)	0.039
The eyes are more than one Chi away from the book
Never	Reference
Sometimes	1.514 (0.919, 2.494)	0.103	0.522 (0.280, 0.974)	0.041
Usually	1.491 (0.864, 2.575)	0.152	0.492 (0.253, 0.956)	0.036
Always	0.925 (0.522, 1.640)	0.790	0.309 (0.150, 0.635)	0.001
The finger is about one Cun away from the tip of the nose
Never	Reference
Sometimes	0.613 (0.390, 0.962)	0.033	1.010 (0.620, 1.646)	0.967
Usually	0.782 (0.489, 1.249)	0.303	0.673 (0.413, 1.094)	0.110
Always	0.871 (0.554, 1.370)	0.550	0.925 (0.574, 1.491)	0.748
Does your teacher remind you that your reading and writing posture is not correct?
Never	Reference
Sometimes	1.029 (0.705, 1.501)	0.882	1.011 (0.677, 1.508)	0.959
Usually	0.808 (0.516, 1.266)	0.353	0.840 (0.519, 1.359)	0.478
Always	0.617 (0.370, 1.028)	0.064	0.919 (0.538, 1.568)	0.757
Do your parents remind you that your reading and writing posture is not correct?
Never	Reference
Sometimes	1.106 (0.701, 1.744)	0.666	1.431 (0.839, 2.441)	0.189
Usually	1.215 (0.740, 1.995)	0.440	2.032 (1.143, 3.614)	0.016
Always	2.222 (1.276, 3.867)	0.005	1.903 (1.051, 3.445)	0.034

The associations between reading and writing posture and myopia in different school types were similar (Table 3). After adjusting for gender and age, the eyes are more than one Chi away from the book was identified as a protective factor in both primary school (Always: 0.545 (0.300, 0.989)) and middle school (Always: 0.371 (0.154, 0.897)). And compared with the middle school students who choose "never" for "the finger is about one Cun away from the tip of the nose", the OR and 95% CI for subjects who choose "sometimes" were 0.411 (0.212, 0.794). Still, the chest is more than one fist from the edge of the table was a risk factor in middle school students and parents remind of reading and writing postures was a risk factor in primary school students.

Table 3

Logistic regression of myopia-related factors by school type.
Items	Primary School		Middle School		High School
Items	OR (95% CI)	P value	OR (95% CI)	P value	OR (95% CI)	P value
Gender	1.320 (1.021, 1.707)	0.034	1.330 (0.963, 1.838)	0.084	1.499 (0.985, 2.282)	0.059
Age	1.546 (1.327, 1.801)	< 0.001	1.154 (0.968, 1.375)	0.111	0.817 (0.651, 1.027)	0.083
The chest is more than one fist from the edge of the table
Never	Reference
Sometimes	1.251 (0.762, 2.053)	0.376	1.931 (0.948, 3.935)	0.070	0.496 (0.168, 1.470)	0.206
Usually	1.540 (0.912, 2.600)	0.107	3.600 (1.663, 7.795)	0.001	0.365 (0.122, 1.093)	0.072
Always	1.703 (0.968, 2.996)	0.065	2.792 (1.246, 6.257)	0.013	0.329 (0.106, 1.021)	0.054
The eyes are more than one Chi away from the book
Never	Reference
Sometimes	0.777 (0.463, 1.304)	0.339	1.015 (0.467, 2.204)	0.970	1.858 (0.811, 4.258)	0.143
Usually	0.969 (0.549, 1.709)	0.913	0.575 (0.252, 1.309)	0.187	1.799 (0.736, 4.400)	0.198
Always	0.545 (0.300, 0.989)	0.046	0.371 (0.154, 0.897)	0.028	1.169 (0.425, 3.218)	0.762
The finger is about one Cun away from the tip of the nose
Never	Reference
Sometimes	1.001 (0.625, 1.603)	0.996	0.411 (0.212, 0.794)	0.008	0.855 (0.418, 1.745)	0.666
Usually	0.721 (0.447, 1.164)	0.181	0.634 (0.322, 1.248)	0.187	0.790 (0.375, 1.666)	0.536
Always	0.960 (0.610, 1.509)	0.858	0.659 (0.336, 1.293)	0.225	1.232 (0.590, 2.576)	0.578
Does your teacher remind you that your reading and writing posture is not correct?
Never	Reference
Sometimes	0.928 (0.604, 1.424)	0.731	1.026 (0.617, 1.705)	0.921	1.150 (0.683, 1.938)	0.599
Usually	0.885 (0.542, 1.444)	0.625	0.863 (0.472, 1.581)	0.634	0.549 (0.278, 1.086)	0.085
Always	0.729 (0.435, 1.223)	0.231	0.925 (0.470, 1.817)	0.820	0.647 (0.202, 2.077)	0.464
Do your parents remind you that your reading and writing posture is not correct?
Never	Reference
Sometimes	1.308 (0.764, 2.239)	0.328	1.336 (0.710, 2.513)	0.369	0.905 (0.464, 1.764)	0.770
Usually	1.560 (0.869, 2.801)	0.137	1.386 (0.706, 2.722)	0.343	1.517 (0.723, 3.182)	0.271
Always	1.958 (1.073, 3.574)	0.029	1.911 (0.933, 3.916)	0.077	2.489 (0.875, 7.079)	0.087

The myopia prevalence of school students in our study was comparable with figures reported from other provinces and cities in China. A study covering 6 provinces in China discovered the prevalence of myopia among primary and middle school students was 55.7%, in which the prevalence was 35.8% in age group 6–8 years, 58.9% in age group 10–12 years, 73.4% in age group 13–15 years and 81.2% in age group 16–18 years [10, 11]. Compared with school students in other countries, myopia prevalence in our study population was considerably higher. The Ireland Eye Study examined 1626 participants, and the prevalence of myopia in participants aged 6–7 years old and aged 12–13 years old was 3.3% and 19.9%, respectively [12]. And Jorge Jorge et al. revealed the myopia prevalence of first-year university students in Portugal was only 23.4% [13].

Reading and writing posture can affect the pleasure and effectiveness of reading and writing as well as retinal image quality, convergence and accommodation demands, and binocular comfort during the process [14]. Through these factors, some investigators also consider reading and writing posture may be an important factor in the development of myopia [15–17].

In our study, we identified keeping distance from the eyes to the book and from the finger to the nose were protective factors for myopia. These findings were consistent with the previous studies. Jinhua Bao et al. published their study about close working distances were observed for Chinese myopic schoolchildren [18]. In the study of Lijuan Wu et al., the logistic regression showed that shorter near work distance to be a risk factor for myopia in high school students in Beijing (OR = 1.87; 95%CI = 1.55–2.26) [19]. In addition, reading behavior is not a fixed entity but differs with grade level and reading condition, which also suggests that reading behavior can be altered through better ergonomics and text design that may reduce myopia and help school students read better [20].

However, keeping distance from the chest to the table and parents remind of reading and writing postures were identified as risk factors for myopia, which are on the contrary to our perception. In our opinion, the distance between the chest and the edge of the table is restricted after all, and the influence to the myopia is limited too. This statistically significant result needs to be verified in a larger population sample. And in the question about the remind of reading and writing postures, we believed there was prevalence-incidence bias existing. Since school students got myopic, their parents will pay more attention to the reading and writing posture and put in more reminds, which will cause that parents remind to be a risk factor.

There were still some limitations in our study. Firstly, we mainly explored the associations between reading and writing posture and myopia, and there were still certain other myopia related factors we didn't include in our study. Secondly, there were recall bias and prevalence-incidence bias in our study due to the study design. Thirdly, the sample size is limited in our study and the results need to be verified in a larger population in the future.

In conclusion, keeping appropriate distance between the eyes and the book may be good for myopia prevention and control. We hope this work will bring educational and public health benefits to form appropriate reading and writing posture.

Competing Interests

The authors declare no competing interests and no potential conflict of interest.

Funding Info

This study was supported by Ningbo public welfare science and technology project (No. 202002N3187) and Ningbo medical science and technology project (No. 2018A68).

Author contribution

Study design: Danjie Jiang, Yan Zhang

Data acquisition: Hua Gao, Yanbo Guo, Shaoying Zhou

Statistical analysis: Danjie Jiang, Bijun Shi

Manuscript preparation and editing: Danjie Jiang

Manuscript revision/review: Yan Zhang

Data Availability

Animal Research (Ethics)

Not Applicable.

Consent to Participate (Ethics)

Informed consent was obtained from all individual participants included in the study.

Consent to Publish (Ethics)

The authors affirm that human research participants provided informed consent for publication.

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Associations Between Reading and Writing Posture and Myopia Among School Students in Ningbo, China

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