The Study
Smartwatch Measures of Outdoor Exposure and Myopia in Children
This study watched kids with smartwatches to see if being outside in bright light for a while was linked to their eyes getting less nearsighted. It found a pattern—kids who spent longer outside in bright light tended to have less eye change—but it didn’t prove that being outside caused the change.
Analysis score
Maximum 72 for a cohort study.
Where the score came from
Kids who spend time outside in bright sunlight may not become nearsighted as fast. This study found that it’s not just how long they’re outside, but how bright and how long the sunlight lasts in one go.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 552 / 100
Quality score
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Key takeaways
Summary
Based on the study abstract and findings.
- 1This small change adds up over years—enough to delay or reduce nearsightedness, especially if kids replace short, dim outdoor time with longer, brighter bouts.
- 2Kids who got at least 15 minutes of sunlight brighter than 2000 lux (like bright daylight) had their eyes change less by 0.006–0.007 diopters each year.
- 3Most kids in Shanghai got only 90 minutes total outside per day.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
JAMA Network Open
Year
2024
Authors
Jun Chen, Jingjing Wang, Ziyi Qi, Shang Liu, Lingyi Zhao, Bo Zhang, Kaige Dong, L. Du, Jinliuxing Yang, Haidong Zou, Xiangui He, Xun Xu
Related Content
Claims (6)
The rise in nearsightedness over the past several decades is due to changes in the environment, not changes in human genes.
Children aged 7 to 9 who spend at least 15 minutes daily in outdoor light of 2000 lux or brighter show a slower progression of nearsightedness by 0.006 to 0.007 diopters per year compared to those who do not, and the timing and pattern of light exposure matter for eye development.
Children who spend time outdoors with higher sunlight intensity experience a reduced rate of myopic shift, and 56.2% of this reduction is due to the combined effect of both factors together, not either one alone.
Replacing shorter or dimmer outdoor time with outdoor time lasting at least 15 minutes and exposed to at least 2000 lux is associated with less progression of nearsightedness.
Children aged 7–9 in Shanghai spend an average of 90 minutes per day outdoors under 2345 lux of sunlight, a level lower than in other countries and not enough to fully reduce the risk of myopia.
Children exposed to outdoor light for less than 15 minutes, even under bright sunlight, do not experience a measurable reduction in the progression of nearsightedness.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.