Role of various types of outdoor activities for school-aged children myopia in Fengyang County, Chuzhou City: a cross-sectional study

Abstract

Objectives

This study aimed to assess the association between various types of outdoor activities and myopia among school-aged children.

Design

A cross-sectional study.

Setting

Fengyang County, Chuzhou City, Anhui Province.

Participants

A total of 2123 students aged 9–19 years (mean 14.60±2.04 years) were recruited from two primary schools, four junior high schools and eight high schools between October and December 2023. 2066 students were included in the final analysis, comprising 1151 boys and 915 girls.

Main outcome measures: Daily time for various types of outdoor activities and eye parameters.

Results

Of the 2066 students enrolled, 85.04% (1757) were diagnosed with myopia. On adjustment for confounding variables, both the total (OR=0.82, 95% CI: 0.73 to 0.92, p=0.001) and low-intensity outdoor activities (OR=0.73, 95% CI: 0.58 to 0.92, p=0.008) exhibited significant associations with the presence of myopia. A gender-based subgroup analysis revealed that daily total outdoor activity hours emerged as a protective factor against myopia in male students (OR=0.83, 95% CI: 0.72 to 0.96, p=0.014), whereas for females, daily medium-intensity outdoor activities were identified as a protective factor (OR=0.44, 95% CI: 0.20 to 0.96, p=0.040). Stratified by educational level, our findings indicated that both daily total outdoor activity (OR=0.59; 95% CI: 0.46 to 0.77, p<0.001) and high-intensity outdoor activities (OR=0.44; 95% CI: 0.21 to 0.91, p=0.026) were beneficial in preventing myopia among students in primary grades 4 to 6. Conversely, for high school students, only daily low-intensity outdoor activities demonstrated a protective effect against myopia (OR=0.69; 95% CI: 0.50 to 0.94, p=0.020).

Conclusions

Outdoor activities, particularly those of low intensity, may offer a protective effect against the development of myopia in school-aged children.

STRENGTHS AND LIMITATIONS OF THIS STUDY.

• This study assessed the prevalence of myopia and outdoor activities status of schoolchildren in Fengyang County, Chuzhou City, Anhui.

• This study has divided the outdoor activities more delicately according to the intensity of the activity.

• This study encompasses a broad spectrum of student ages and rigorously accounts for numerous potential confounding variables.

• Gender and educational stage stratification were employed to conduct a comprehensive assessment of outdoor activities among school-aged children.

• This cross-sectional study employed purposive sampling, potentially introducing selection bias; second, the utilisation of questionnaires could lead to recall bias; and finally, the cycloplegic refraction and ocular biometric measurement were not conducted in the study.

Introduction

Myopia, one of the most common visual impairments, has become a global public health issue worldwide.^{1 2} It was predicted that the global myopic population will reach nearly 5 billion by 2050, with approximately 10% of the total global population suffering from high myopia, indicating that nearly 1 billion people will have suffered irreversible vision loss due to the complications of high myopia,³ including myopic retinopathy, myopic glaucoma and retinal detachments.⁴ In several East Asian countries, myopia has emerged as the most common reversible blinding eye disease.⁵ Meanwhile, the prevalence of myopia among the Chinese population has increased dramatically, exhibiting a trend towards younger ages,⁶ with nearly 90% of Chinese teenagers and young adults suffering from myopia.^{7 8}

The increased prevalence of myopia not only hinders the physical and mental health development of children and adolescents but also brings about huge social, educational and economic consequences to families and society.^{1 9} In China, there is an urgent need to identify the possible factors associated with myopia in order to prevent and control its occurrence and development in a timely manner. Genetic and environmental factors have been found to contribute to the development of myopia.^{10 11} Attempting to reduce myopia risk through direct genetic modification presents significant challenges. In view of this, research efforts have been concentrated on exploring the environmental and behavioural factors linked to the progression of myopia, aiming to identify factors that could potentially influence the onset of myopia and subsequently implement measures to mitigate its risk.

A large number of research studies have confirmed that an increase in time spent outdoors is significantly associated with a lower prevalence of myopia.12,15 However, most of these studies relied solely on questionnaires to ascertain students’ daily total outdoor time or categorically divided it into outdoor leisure and sports time, thereby failing to provide a more nuanced classification of outdoor activities. A recent study has examined the impact of outdoor activity time and outdoor exposure patterns, which were obtained using a smartwatch, on the development of myopia. Although smartwatches have demonstrated a high degree of accuracy in measuring outdoor exposure parameters, it is difficult to disseminate such devices to a large sample population, due to high economic costs.¹⁶

To obtain more detailed data on outdoor activities, we adopted a more comprehensive questionnaire. Although most previous studies have emphasised the protective effects of outdoor activities on myopia, their focus has primarily been on the duration and intensity of outdoor light exposure. The relationship between the intensity of outdoor activities and myopia requires further evidence. The present study aims to investigate the specifics of outdoor activities and explore the potential association between different levels of intensity of outdoor sports and myopia among school-aged children in Chuzhou City, Anhui Province. It provides a theoretical basis for the formulation of relevant policies to guide students’ outdoor activities in the region and contributes to the prevention, control and intervention of myopia among children and adolescents in China.

Methods

Study population

This school-based cross-sectional study was conducted between October and December 2023. The purposive sampling method was used to select the schools. Specifically, one primary school, two junior high schools and four high schools were selected from both urban and rural areas of Fengyang County, Chuzhou City, Anhui Province. A total of 14 schools, including two primary schools, four junior high schools and eight high schools, were included in the study. One class from each grade within the selected schools was randomly selected. Primary school students in grades 1–3 had difficulty completing the questionnaire independently and were therefore excluded from the study. All students in the selected classes were invited, and after the nature of the study was explained, informed consent for each child was obtained from their guardians. Students who are non-voluntary or unable to independently complete the study participants, those with a history of psychiatric disorders, those suffering from internet addiction or drug abuse, those with other ocular diseases or those who have undergone ocular surgery within the past 3 months will be excluded from this study. Additionally, verbal assent was obtained from each student. The present study has been approved by the Medical Ethics Committee of Anhui Medical University (YX2022058) and has been conducted in accordance with the principles of the Declaration of Helsinki.

Measurements

All participants completed a questionnaire under the guidance of the optometrists. We sought advice regarding the questionnaire from experts in myopia prevention and epidemiological research and subsequently developed the questionnaire based on their recommendations. Following the completion of the questionnaire, the participants underwent standardised eye measurements.

Outdoor time

The various outdoor activities are categorised into three types of activities based on their intensity: low intensity, medium intensity and high intensity. Low-intensity outdoor activities primarily encompass activities with a relatively low physical load, such as outdoor walking, picnicking and strolling in the park. Medium-intensity outdoor activities involve activities that impose a moderate physical load, such as outdoor cycling and jogging. High-intensity outdoor activities involve activities with a substantial physical load, such as outdoor running, basketball and rope skipping. The number of hours spent per day in the last week was recorded separately for each category. Separate recordings were also taken for school weekdays and school weekends. Participants were also asked: ‘How many hours per day did you spend on total outdoor activities (comprising of outdoor leisure and sports) on weekdays/weekends over the past week?’ The average daily duration of total outdoor activities and low-/medium-/high-intensity outdoor activities was calculated using the following formula: (hours spent on weekdays×5+ hours spent on weekends×2)/7.

Covariates

Gender (male/female), residency (urban/rural), school grade (primary school/junior high school/high school), study status, family status, screen status and sleep status were considered as covariates. Study status’ information mainly includes academic performance (poor/moderate/good), learning burden (light/average/heavy), extracurricular tutorial classes (yes/no), read-write distance (0–10 cm/10–20 cm/20–30 cm/30–40 cm) and study time (hour per day; weekday and weekend). Family status’ information mainly includes only child or not (yes/no), parental education (less than primary school/junior high school/high or secondary vocational school/university or college and above), parental myopia status (none/one myopia/both myopia), monthly family income (<¥1000/¥1000–¥2500/¥2500–¥4000/>¥4000) and home lighting illumination (dark/fair/bright). Screen status’ information mainly includes near screen time (ie, time for televisions, computers and mobiles/iPads/game consoles; hours per day; weekday and weekend), distance of watching Television (0–1 m/1–2 m/2–3 m/>3 m), distance of playing with computers (40–50 cm/50–60 cm/60–70 cm/70–80 cm) and distance of playing mobiles/iPads/game consoles (0–10 cm/10–20 cm/20–30 cm/30–40 cm). Sleep status information mainly includes time of falling asleep (<15 min/16–30 min/31–60 min/>60 min), sleeping with the light on (yes/no), sleep quality (bad/average/good) and sleep time (hours per day; weekdays and weekend). The average duration of study, screen and sleep per day was calculated using the following formula: (hours spent on weekdays×5+ hours spent on weekends×2)/7.

Eye measurements

Eye examinations were conducted at temporary stations set up in the school. All students underwent distance uncorrected visual acuity measurement and non-cycloplegic autorefraction, both procedures performed by experienced senior optometrists in a well-lit room. Visual acuity was measured at a distance of 5 m using a standard logarithmic visual acuity E chart (GB11533-2011), resulting in a 5-mark record. Refractive status was measured using an auto-refractor under non-ciliary muscle paralysis, and three non-cycloplegic autorefraction measurements per eye were averaged to calculate the mean spherical equivalent (SE). If any two of the three results were greater than 0.50 diopters (D) apart, additional checks were conducted during the same visit. The SE of the refractive error was calculated as the sum of the spherical power +1/2 cylindrical power. To more comprehensively reflect children’s visual function and enhance the accuracy and sensitivity of screening, myopia was defined according to a visual acuity of less than 5.0 and an SE of ≤−0.5D in either eye.¹⁷

Statistical analysis

EpiData software 3.1 was used for parallel double entry and validation of questionnaire data. Statistical analyses were performed using the Statistical Package for the Social Sciences (V.25.0; IBM Corp., Chicago, IL, USA). The normality of the continuous variable distribution was confirmed through the Shapiro-Wilk test. All continuous variables were presented as median (IQR), whereas the categorical variables were expressed as number (percentage). The correlations between myopia and various covariates were evaluated using the χ² test for categorical variables and the rank sum test for continuous variables. Parameters demonstrating a myopia-specific association in the χ² or rank sum test were further verified using univariate regression analysis. Parameters exhibiting a univariate association with a p value<0.05 were identified as confounders. Multiple logistic regressions were conducted, with the presence of myopia serving as the dependent outcome variable. The main independent variables included hours of total and low-intensity, medium-intensity and high-intensity outdoor activities per day, with adjustments for other covariates. The OR and 95% CI for the parameters were computed. The level of statistical significance was established at p<0.05 (two-sided). Factors having an OR less than 1 were deemed protective against myopia, while those with an OR above 1 were deemed risk factors for myopia.

Patient and public involvement

In this cross-sectional study on myopia among school-aged children, patients (students) and the public, including educational institutions and parents, were first involved during the research design phase through consultations with experts in myopia prevention and epidemiological research to ensure the relevance and applicability of the study to the target population. The research questions and outcome measures were developed based on their priorities, experiences and preferences, particularly focusing on the urgent need to identify factors associated with myopia and the potential protective effects of outdoor activities. They were involved in the study design by contributing to the questionnaire development and ensuring the study’s feasibility and effectiveness through collaboration with educational institutions. During recruitment and conduct, educational institutions facilitated access to the student population, and informed consent from guardians and verbal assent from students were obtained, reflecting their involvement. Although the study did not involve a direct intervention requiring burden assessment, the study design minimised participant burden through efficient data collection processes. For disseminating the study results, patients and the public will be involved by choosing relevant information/results to share, determining the timing and selecting appropriate formats through educational lectures, school announcements and other channels to ensure that the findings are accessible and beneficial to them.

Results

Demographic characteristics of participants

A total of 2123 students aged 9–19 years (mean 14.60±2.04 years) were enrolled in the current study, and 2066 questionnaires were validated for analysis, of which 55.71% (n=1151) were boys and 44.29% (n=915) were girls. Primary 4-6th grade students, middle school students and general high school students accounted for 11.96% (n=247), 35.91% (n=742) and 52.13% (n=1077), respectively. There were 829 participants (40.13%) from rural areas and 1237 participants (59.87%) from urban areas. The overall prevalence of myopia was 85.04%. The prevalence of myopia among boys was 82.10%, which was significantly lower than that of girls (88.74%; χ²: 17.673, p<0.001). The prevalence of myopia among primary 4-6th grade students was 61.54%, while for middle school students and general high school students, it is 85.04% and 90.44%, respectively, implying that the prevalence of myopia generally increased with educational stage (χ²: 131.913, p<0.001). No significant difference in the prevalence of myopia was found between urban (85.04%) and rural area students (85.04%; χ²: 0.000, p=0.999).

Outdoor activity

As shown in table 1, the hours of total outdoor activities and low-intensity, medium-intensity and high-intensity outdoor activities per day for myopic students were significantly less than for non-myopic students (Z: −6.845, p<0.001; Z: −4.550, p<0.001; Z: −3.034, p=0.002; Z: 4.292, p<0.001; respectively). Moreover, there was a clear gender-based difference in the amount of time spent outdoors, with boys spending significantly more time outdoors than girls (Z: −2.016, p=0.044). As the grades increased, the amount of time spent outdoors decreased significantly (H: 163.747, p<0.001). There is no significant difference in the amount of time students spend outdoors between urban and rural areas (Z: −0.502, p=0.615).

Table 1. Status of different categories of outdoor activities.

	Total outdoor activities (hours/day, median (IQR))	Low-intensity outdoor activities (hours/day, median (IQR))	Medium-intensity outdoor activities (hours/day, median (IQR))	High-intensity outdoor activities (hours/day, median (IQR))
Myopia status
No myopia	1.29 (0.71, 2.28)	0.33 (0.14, 0.71)	0.14 (0.00, 0.36)	0.10 (0.00, 0.36)
Myopia	0.86 (0.40, 1.50)	0.25 (0.11, 0.43)	0.10 (0.00, 0.29)	0.05 (0.00, 0.21)
P value*	<0.001	<0.001	0.002	<0.001
Gender
Male	1.00 (0.48, 1.71)	0.29 (0.14, 0.50)	0.14 (0.00, 0.30)	0.11 (0.00, 0.29)
Female	0.88 (0.40, 1.57)	0.24 (0.10, 0.43)	0.07 (0.00, 0.21)	0.00 (0.00, 0.14)
P value*	0.044	0.031	<0.001	<0.001
Residency
Rural	0.93 (0.45, 1.57)	0.28 (0.11, 0.48)	0.09 (0.00, 0.24)	0.03 (0.00, 0.21)
Urban	0.99 (0.44, 1.69)	0.29 (0.11, 0.50)	0.12 (0.00, 0.29)	0.07 (0.00, 0.29)
P value*	0.615	0.801	0.021	<0.001
Grade
Primary school	1.71 (1.00, 2.74)	0.58 (0.29, 1.00)	0.25 (0.09, 0.62)	0.19 (0.05, 0.43)
Junior high school	1.00 (0.50, 1.64)	0.29 (0.10, 0.43)	0.12 (0.00, 0.29)	0.09 (0.00, 0.29)
High school	0.71 (0.33, 1.43)	0.21 (0.09, 0.43)	0.07 (0.00, 0.24)	0.00 (0.00, 0.19)
P value†	<0.001	<0.001	<0.001	<0.001

Bold font data indicate p<0.05.

^*Compared by Mann-Whitney U test.

^†Compared by Kruskal-Wallis H test.

Other covariates

As shown in online supplemental material 1, univariate analysis indicated that gender (χ²: 17.673, p<0.001), school grade (χ²: 131.913, p<0.001), learning burden (χ²: 25.675, p<0.001), extracurricular tutorial classes (χ²:21.161, p<0.001), hours of study per day (Z: −6.520, p<0.001), parental myopia (χ²: 20.056, p<0.001), only child or not (χ²: 5.019, p=0.025), hours of screens per day (Z: −2.998, p=0.003), sleep quality (χ²: 18.381, p<0.001) and hours of sleeping per day (Z: −7.121, p<0.001) were significantly associated with the prevalence of myopia. Non-myopic students played with mobiles further away (χ²: 10.929, p=0.012), but this difference did not reach statistical significance in the univariate regression analysis. In contrast, mother’s education level of junior high school (vs less than primary school; OR=0.67, 95% CI: 0.47 to 0.95, p=0.023) and university or college and above (vs less than primary school; OR=0.61, 95% CI: 0.37 to 0.98, p=0.043) was considered a protective factor for myopia in the univariate regression analysis.

Outdoor activity and myopia

All statistically significant covariates in the univariate regression analysis were incorporated into the multivariate logistic regression analysis and mutually adjusted (online supplemental material 2). After adjusting for possible confounders, the hours of total outdoor activities per day (OR=0.82, 95% CI: 0.73 to 0.92, p=0.001) and low-intensity outdoor activities (OR=0.73, 95% CI: 0.58 to 0.92, p=0.008) were identified as associated factors for preventing myopia.

Considering the differences in the prevalence of myopia among students of different genders and educational stages, the subgroup analysis was performed to explore the protective effects of outdoor activities against myopia in different groups of students (table 2). For the subgroup analysis performed by gender, the hours of total outdoor activity per day were identified as an associated factor for preventing myopia in boys (OR=0.83, 95% CI: 0.72 to 0.96, p=0.014) but not seen in girls. In contrast, the hours of medium-intensity outdoor activities per day were identified as an associated factor for preventing myopia in girls (OR=0.44, 95% CI: 0.20 to 0.96, p=0.040) but not seen in boys. The results of subgroup analysis performed by educational stage revealed that more hours of total outdoor activity (OR=0.59, 95% CI: 0.46 to 0.77, p<0.001) and high-intensity outdoor activities (OR=0.44, 95% CI: 0.21 to 0.91, p=0.026) per day were beneficial in preventing myopia for primary 4-6th grade students, while only the hours of low-intensity outdoor activities (OR=0.69, 95% CI: 0.50 to 0.94, p=0.020) per day showed a protective effect against myopia in high school students. These observations were not observed in junior high school students.

Table 2. The association between myopia and outdoor activities from multiple logistic regression analysis.

Outdoor activities	Total		Low intensity		Medium intensity		High intensity
	AOR (95% CI)	P value	AOR (95% CI)	P value	AOR (95% CI)	P value	AOR (95% CI)	P value
Model 1	0.82 (0.73 to 0.92)	0.001	0.73 (0.58 to 0.92)	0.008	1.04 (0.79 to 1.36)	0.796	0.97 (0.71 to 1.32)	0.835
Model 2	0.83 (0.72 to 0.96)	0.014	0.75 (0.56 to 1.01)	0.057	1.15 (0.84 to 1.59)	0.379	0.84 (0.57 to 1.22)	0.348
Model 3	0.81 (0.65 to 1.00)	0.051	0.73 (0.50 to 1.07)	0.102	0.44 (0.20 to 0.96)	0.040	2.39 (0.76 to 7.52)	0.136
Model 4	0.59 (0.46 to 0.77)	<0.001	0.92 (0.56 to 1.50)	0.730	1.47 (0.89 to 2.43)	0.137	0.44 (0.21 to 0.91)	0.026
Model 5	0.82 (0.66 to 1.00)	0.055	0.90 (0.51 to 1.58)	0.716	1.19 (0.61 to 2.34)	0.606	1.29 (0.59 to 2.79)	0.522
Model 6	1.01 (0.81 to 1.26)	0.925	0.69 (0.50 to 0.94)	0.020	0.77 (0.46 to 1.28)	0.314	1.07 (0.57 to 2.00)	0.844

Model 1 for total included gender, grade, learning burden, extracurricular tutorial classes, study time, only child or not, mother’s education, parental myopia status, screen time, sleep quality and sleep time. Model 2 for boys and model 3 for girls include all variables in model 1 except gender. Model 4 for primary school, model 5 for junior high school and model 6 for high school include all variables in model 1 except grade.

Bold font data indicate p<0.05.

AOR, adjusted OR.;

Discussion

While numerous prior studies have identified an association between myopia prevalence and time spent outdoors, our school-based cross-sectional study provides a more comprehensive analysis of outdoor activity patterns, enabling a nuanced examination of the relationship between varying intensities of outdoor activities and myopia. Our findings support a protective role of both total and low-intensity outdoor activities against myopia in school-aged children in Anhui.

The results of our study reaffirm the associations observed in previous research regarding the impact of outdoor time on myopia. In 2008, Rose et al¹² conducted a study involving 3132 children aged 6 and 12 years, revealing an association between increased time spent outdoors and a lower prevalence of myopia after controlling for confounding variables. This finding garnered substantial academic attention, catalysing extensive research into the relationship between outdoor activity and myopia. The Avon Longitudinal Study of Parents and Children similarly identified a correlation between the onset of myopia and both time spent outdoors and physical activity, with outdoor time demonstrating a more significant influence.¹⁸ Consistent with these findings, our study observed that only low-intensity outdoor activities had a statistically significant protective effect against myopia when outdoor activity intensity was examined separately. Conversely, the protective effect of medium- and high-intensity outdoor activities diminished after multivariate regression analysis, becoming less pronounced. This study reinforces the hypothesis that it is the ‘outdoor’ element of activities, rather than the physical activity itself, that exerts a protective effect against myopia.

A 2½ year longitudinal survey by Jiang et al¹⁹ involving 1388 students in grades one through three found that children without myopia spent more time outdoors (1.92 hours/day) than those with new-onset myopia (1.81 hours/day). High levels of outdoor time were associated with a 58% reduction in the risk of new-onset myopia among children with one myopic parent, suggesting that outdoor activity may mitigate genetic risk to some extent. Similarly, an Australian risk factor study of 2103 children aged 6 and 12 years found that children with new-onset myopia spent less time outdoors over a 5–6 year follow-up than those without myopia, with this association particularly pronounced among younger children (6 years).²⁰ Further, Guo et al²¹ reported that children in urban areas of Beijing had a higher prevalence of myopia and significantly fewer outdoor hours compared with their rural counterparts, indicating that outdoor activity hours may partly explain regional differences in myopia prevalence. However, our study did not observe a significant difference in outdoor activity between urban and rural areas, possibly due to the relatively close geographical proximity of these regions. Wu et al²² conducted a prospective intervention trial among Taiwanese students aged 7–15 in China, where children in the intervention group were encouraged to engage in outdoor activities during recess, while those in the control group received no intervention. After 1 year, the new-onset myopia rate in the intervention group (8.41%) was significantly lower than in the control group (17.65%). Similarly, He et al²³ conducted a 3-year randomised controlled trial with first-grade students across 12 primary schools, introducing a 40-min daily outdoor session into the curriculum for the intervention group. The results showed a significantly lower cumulative incidence of myopia in the intervention group (30.4%) compared with the control group (39.5%).

Our study revealed a gender-specific difference in the protective effect of outdoor activities against myopia, with a significant association observed between outdoor activity and reduced myopia prevalence in boys, but not in girls. This finding stands in contrast to the study by Guo et al,²¹ which reported no gender differences in the effect of outdoor activities on eye axis growth and myopia incidence. A potential explanation for this discrepancy may lie in the broader age range included in our study, spanning students from grade 4 of primary school to grade 3 of high school, which may highlight the influence of age on gender-related differences. In contrast, Guo et al focused solely on students in grades 1 and 4 of primary school, possibly limiting the visibility of gender effects on myopia correlates within younger age groups.

The precise mechanisms linking reduced exposure to outdoor environments with an elevated risk of myopia remain elusive. Rose et al¹² propose that dopamine (DA) may play a crucial role in the mechanism by which outdoor activities protect against myopia. Exposure to light in outdoor environments stimulates retinal DA production, which is involved in establishing the retina’s intrinsic circadian network, modulating neural signalling and inhibiting ocular growth, thus providing a protective effect on vision.^{24 25} Additionally, the higher light intensity outdoors induces a physiological pupil constriction response, which enhances the depth of field and the clarity of the retinal image, thereby potentially reducing axial elongation and slowing myopia progression.²⁶ The differing spectral compositions of natural daylight and indoor lighting may also contribute to the protective effects of outdoor activities, a hypothesis supported by findings from animal studies.27,29

Several limitations of this study should be noted. First, purposive sampling was employed due to practical constraints, which may introduce selection bias and affect the representativeness of the sample. Second, a self-reported questionnaire was used in the present research for the purpose of gathering information on the duration of students’ engagement in outdoor activities over the previous week, accompanied by a comprehensive categorisation of the various types of outdoor activities. Nevertheless, the presence of potential recall inaccuracies may hinder students’ ability to precisely indicate the exact quantity of time they spent outdoors. Employing objective measures for outdoor activity duration could provide a more robust approach in future research. Additionally, cycloplegic refraction was not conducted, which may have introduced bias in the assessment of myopia prevalence, and the absence of ocular biometric data limits the comprehensiveness of the findings.

Conclusion

In conclusion, our study, which covers a wide age range of students and controls for considerable confounders, is in agreement with previous research that a greater number of hours spent in outdoor activities by school-aged children has significant benefits in preventing the development of myopia, with a pivotal emphasis on the contribution of low-intensity outdoor activities. In order to further investigate the association between outdoor activity intensity and myopia development, it is necessary to conduct larger and prospective studies with objectively measured outdoor activity data in the future. Nonetheless, in the face of the growing myopia problem, educational institutions and parents should actively encourage students to participate in outdoor activities as an effective means of reducing myopia.

The funding agency associated with this research did not participate in the design of the study, the collection, analysis, or interpretation of data, nor in the writing of this manuscript. Furthermore, the funding agency had no direct or indirect influence on the publication of this paper.

Data availability statement

Data are available upon reasonable request.