More outdoor time led to less myopic shift in children
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Key takeaways:
- Children spent an average of 90 minutes outdoors per day.
- Exposures of at least 15 continuous minutes led to less myopic shift than shorter exposures.
Spending at least 15 minutes at a time outside appeared to lead to less myopic shift among elementary school students, according to data published in JAMA Network Open.
“Previous studies have demonstrated that spending more time outdoors is an effective intervention for myopia,” Jun Chen, PhD, from the Shanghai Eye Diseases Prevention & Treatment Center at Shanghai Eye Hospital, and colleagues wrote. “The previous findings emphasized the impact of daily time outdoors and sunlight intensity on myopia, indicating a potential collaborative association between time outdoors and sunlight intensity in preventing the onset of myopia.”
The prospective cohort study included 2,976 children (51.2% girls; mean age, 7.2 years) without myopia — or nearsightedness — who participated in the Shanghai Time Outside to Reduce Myopia (STORM) trial, which recruited students from Shanghai schools to track their time spent outdoors. The researchers provided the children with smartwatches to measure their outdoor time and collected data from the watches between December 2017 to December 2018.
According to the findings, the children in the study spent an average of 90 minutes (SD, 28 minutes) outdoors per day and were exposed to an average sunlight intensity of 2,345 lux (SD, 486 lux). The most common time periods spent outdoors were in the morning, at midday and in the afternoon. The median time for one period of outdoor exposure was 11 minutes (interquartile range [IQR], 5-23 minutes) and median sunlight intensity was 2,061 (IQR, 1,060-4,812) lux.
At baseline, the average spherical equivalence was 1.26 diopter (SD, 0.67 diopter [D]) and axial length was 22.74 mm (SD, 0.69 mm).
Sunlight intensity and daily time outdoors showed an additive interaction on myopic shift (interaction effect estimate, –0.065 D; 95% CI, –0.098 D to –0.032 D; P < .001). Spending longer than 15 minutes at a time outdoors was “protective against myopic shift, with the association increasing with sunlight intensity,” the researchers wrote.
“Continuous outdoor exposure of at least 15 minutes accompanied with no less than 2,000 lux sunlight intensity was associated with less myopic shift,” they wrote. “These findings suggest that future outdoor intervention programs should focus not only on daily time outdoors but also the outdoor exposure patterns to prevent myopia.”
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