Spending more time outdoors may prevent short-sightedness in children

By Sally Robertson, B.Sc.Sep 17 2015

A Chinese study has shown a decreased incidence of short-sightedness (myopia) in children who spend extra time outdoors.

Adding an extra 40 minutes of outdoor activity to children’s usual time outdoors reduced the incidence of myopia over a three year period, providing the first indicator that myopia may actually be preventable.

Christopher Quinn, president at Omni Eye Services in Iselin, New Jersey, said:

This study suggests that increased outdoor activity, which presumably means less time performing near point tasks, is mildly protective for the development of myopia.”

Myopia has reached epidemic levels in some parts of East and Southeast Asia, where up to 90% of high school graduates are now short-sighted. However, there is currently no effective intervention to prevent young adults developing myopia, even though vision scientists have long suspected that tasks requiring prolonged near visual effort may be a risk factor for the condition.

For the current study, Mingguang He (Sun Yat-sen University, Guangzhou, China) and colleagues conducted a randomized trial involving more than 1,800 first graders (aged an average of 6.6 years) from 12 primary schools in Guangzhou. They split the children into two groups. The first group were assigned an extra 40-minute class of outdoor activities, added to each school day, and parents were asked to encourage the children to spend more time outdoors when they were not at school. The second group continued with their usual pattern of outdoor activity. The children were followed for a three year period to assess the incidence rate of myopia among children who did not have the condition at baseline.

As reported in JAMA, the 3-year cumulative incidence rate of myopia was 30.4% among children from the intervention group, compared with 39.5% among children from the control group.

He and colleagues wrote:

Our study achieved an absolute difference of 9.1 percent in the incidence rate of myopia, representing a 23 percent relative reduction in incident myopia after 3 years.”

Although the reduction was not us much as they had anticipated, the researchers say the finding is still clinically important because small children who develop short-sightedness are most likely to progress to high myopia, which increases the risk of pathological myopia. Therefore, anything that might delay the onset or progression of myopia could provide long-term eye health benefits.

Quinn also points out that although short-sightedness is not as common in the U.S as it is in Asia, it is still estimated to affect at least 30% of U.S school children. “Further study to determine the exact mechanism by which increased outdoor activities reduce the development of myopia will be helpful in guiding public health strategies to reduce the development of myopia,” he suggests.