Time outdoors reduces myopia risk in subset of children
Researchers have found that nonmyopic children 7 to 10 years old have a significantly reduced risk of myopia onset if they spend more time outdoors.
Mutti and colleagues reported at the Association for Research in Vision and Ophthalmology that because previous studies have shown a protective effect of outdoor time, they sought to evaluate this effect in a range of ages.
They studied children involved in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error study who did not have myopia when they were enrolled at the ages of 6 to 12 years, according to the study abstract. Each of these age groups comprised 549 to 1,854 children.
Parents were surveyed at baseline regarding their children’s time outdoors, and the risk of myopia onset by the age of 14 years and time outdoors was adjusted for sex, ethnicity, number of myopic parents and time spent reading, according to the study.
The 6- to 8-year-old group had the highest proportion of those who became myopic, at 17% to 19%, while 7.3% of those who were 12 years old at baseline became myopic by age 14. Having two myopic parents was linked to an increased risk, while time spent reading had no effect.
“More time spent outdoors (10 more hours per week) significantly reduced the risk of myopia onset for children at baseline ages of 7, 8, 9 and 10 years,” the researchers reported in the abstract, while time outdoors had no effect for those who were 6, 11 or 12 years old at baseline.
The researchers hypothesized on an explanation for the different effect in different age groups: “At younger baseline ages it may involve low statistical power or a greater genetic component to risk.”
Lead author Donald O. Mutti, OD, PhD, FAAO , told Primary Care Optometry News, “Work by others in the U.K. on children as young as 3 and the positive effects at ages 7 to 10 had them still recommending more time outdoors early in childhood.”
The researchers stated in the study: “Lack of effect at older ages may indicate greater difficulty in preserving emmetropia when the eye is larger and closer to the criterion level of myopia.”
Mutti said he and his colleagues, “concluded that older nonmyopic children only 1 to 2 years away from myopia onset may not see the same benefit as younger children. The bottom line message was time may run out; nonmyopic kids should spend time outside early and often.” – by Nancy Hemphill, ELS, FAAO
Mutti DO, et al. Childhood age, time outdoors and the risk of juvenile-onset myopia. Presented at: Association for Research in Vision and Ophthalmology; Honolulu; April 29-May 3, 2018.
Disclosure: Mutti reported no relevant financial disclosures. Please see the full study for all remaining authors’ financial disclosures.