Children who spend time doing activities outdoors appear to have a lower risk of developing nearsightedness, or myopia, as it is medically termed, according to a new report written by a team from Sun Yat-sen University in Guangzhou, China, published in JAMA.
Myopia is "a vision condition in which close objects are seen clearly, but objects farther away appear blurred."
It occurs if the eyeball is too long, or the cornea - the clear front cover of the eye - has too much curvature. This causes the light entering the eye to be incorrectly focused, and makes distant objects look blurred, according to the American Optometric Association (AOA).
There is some evidence that myopia is hereditary, but research increasingly shows that the visual stress of too much close work may play a role.
The authors of the new report say that the rate of myopia appears to be growing, especially in Europe and the Middle East. In some urban areas of East and Southeast Asia, myopia is now at "epidemic levels" among young adults, affecting 80-90% of high school graduates.
The research team, led by Dr. Mingguang He, PhD, followed 1,903 primary school students over 3 years to explore what difference it would make if one 40-minute session of outdoor activity was added to the school day.
The intervention group consisted of 952 students from six schools, while the control group was made up of 951 students from six other schools. All children were free of myopia at study baseline.
Parents of children in the intervention group were encouraged to engage their children in further outdoor activities at weekends and during holidays, while the children in the control group were to continue their usual routine. The average age of the children was 6.6 years.
Better vision for those who played outdoors
After 3 years, the optical measurements of children were taken and analyzed.
The rate of myopia was 9.1% lower than among children who did not participate in the extra activities. Of the intervention group, 30.4% developed myopia over this time, compared with 39.5% of the control group. This represented a relative reduction of 23% over 3 years.
While describing this as "lower than the anticipated reduction," researchers still believed it was "clinically important." Small children who develop myopia early are more likely to develop more severe forms later in life, so delaying the onset can provide optical health benefits in the long run.
- There were 30,357 new cases of myopia in the US in 2010, compared with 34,119 new cases in 2000
- The number of people with myopia in the US is expected to rise from 33 million in 2010 to 43 million in 2050
- Myopia affected 54% of females and 46% of males in the US in 2010.
The team recommends further studies to assess long-term follow-up for the children and investigation into the generalizability of these results.
In a linked editorial, Dr. Michael Rekpa, of John Hopkins University School of Medicine, Baltimore, MD, calls for future studies to include information about the content of the activity, whether or not it can be standardized and how it differs from other studies, in order to inform decisions that could be made by schools regarding the implementation of activities.
Dr. Rekpa adds that "the intervention is essentially free" and may have other health benefits, but warns against prescribing such activities specifically to improve eyesight, as "the effect is likely to be small, and the durability uncertain."
Dr. He told Medical News Today that the outdoor activities undertaken by the children were different every day, and included music, English, drawing and moral lessons, as well as sports. Schools were provided with guidelines by the research team.
While the team did not research the association between specific activities and outcomes, he mentioned that research carried out in Australia has suggested:
"The type of activities are not associated with myopia: it is being outdoors that makes the difference."
Earlier this month, Medical News Today reported that children with a certain gene may be more prone to nearsightedness if they do a lot of close work, such as reading.