(CBC) — For primary school children in China, spending an extra 45 minutes per day outside in a school activity class may reduce the risk of nearsightedness, or "myopia," according to a new study.
In some parts of China, 90 per cent of high school graduates have nearsightedness, and rates are lower but increasing in Europe and the Middle East, the authors write.
"There were some studies suggesting the protective effect of outdoor time in the development of myopia, but most of this evidence is from cross-sectional studies [survey] data that suggest 'association' instead of causality," said lead author Dr. Mingguang He of Sun Yat-sen University in Guangzhou. "Our study, as a randomized trial, is able to prove causality and also provide the high level of evidence to inform public policy."
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