A child gets her eyeglass prescription checked.
National Eye Institute, National Institutes of Health
My parents were right!! A spate of studies over the past decade has found that kids who spend more time outdoors are less likely to develop near-sightedness. Outdoor time seems to protect kids even if they do a lot of “near work” (e.g., reading Goosebumps and Animorphs nonstop) and if their parents are myopic.
When I was a kid, my parents would always tell me to stop reading and go play outside. I would scoff: What kind of parents want their kid to stop reading? But maybe they had a point after all.
A team of Australian researchers recently reviewed major studies since 1993 of kids, myopia and time spent outdoors. They found more than a dozen studies, examining more than 16,000 school-age kids in total, that found children were more likely to be nearsighted or to develop nearsightedness if they spent less time outdoors. A few of the later studies also found that being outdoors protected even those kids who did a lot of near work or had myopic parents. The studies included kids living in Europe, the U.S., Asia, the Middle East and Australia.
The researchers did find three studies, comprising about 4,600 kids, where there was no association between nearsightedness and time spent outdoors. Of those three studies, one looked at a group of children that was predominantly myopic (83 percent of them were nearsighted) and spent very little time outdoors overall (just six hours a week, on average). Another study looked at younger children, aged six months to six years. Nearsightedness is rare in kids that young.
Scientists aren’t sure yet why being outside prevents kids from becoming Miss Four-Eyes early in life. There is some evidence, from studies done in lab mice, that sunlight may trigger the production of the brain chemical dopamine, which in turn prevents eyes from growing elongated. Nearsighted eyes are overly elongated. However, some conflicting studies mean that scientists can’t be sure this is what’s happening in humans.
Scientists also aren’t exactly sure how strongly outdoors time protects kids. Some studies have found a small protective effect, while others have found larger ones, the Australian reviewers report.
Interestingly, the studies that have looked at near work-stuff you do that requires you to focus on something in a close range, such as reading and writing-haven’t consistently shown that it causes nearsightedness. It may be that it’s difficult to calculate exactly how much near work a person does, the Australian team says. In addition, some research groups classify computer and TV time as near work, while others don’t. Televisions are far away enough that they don’t strain the eye too much, while computer use is about half a straining as reading, the Australian team reports.
Some scientists have proposed that frequently looking at far distances helps prevent myopia. That sounds like a good reason for outdoors time’s protective effects, but studies about this seem sparse.
Overall, the strong evidence for outdoors time preventing nearsightedness may be a good reason to get kids out more. There are even ongoing clinical trials in China and Taiwan that are examining whether getting classes of kids outside reduces the number of them who develop myopia later.
Bonus FYIs: Nearsightedness In Hollywood
Do Asians all wear glasses, like they do in the movies?
Nearsightedness is much more common in kids in certain Asian countries than in Western countries. Studies of Singapore, China, Taiwan, Japan and Korea have found that around 80 percent of kids are nearsighted. In the U.S. and Europe, 30 percent to 50 percent of kids are.
However, myopia doesn’t seem to be genetically linked to race. For example, in ethnically diverse Singapore, similar rates of myopia appear in all the ethnicities that live there, including in people of Indian origin, who are more genetically akin to Middle Eastern and European people than East Asian people. Instead, environmental factors seem to make the difference.
Do smart people really all wear glasses?
This Hollywood stereotype touches upon a truth-adults with more education are more likely to be nearsighted. Studies have also found that kids in Singapore with higher exam scores were more likely to be myopic.
This may mean that the duration or intensity with which people do near work does affect their risk for nearsightedness, even though near work studies have been inconsistent, the Australian reviewers wrote.
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