Parents, take note! Allowing kids to play in Sun may help them avoid eyeglasses in later life, say scientists who found that higher exposure to ultraviolet B radiation reduces the risk of nearsightedness.
Researchers from the London School of Hygiene and Tropical Medicine in the UK suggest that exposure to ultraviolet B (UVB) radiation between ages 14 and 29 years is associated with the highest reduction in odds of adult myopia.
Myopia is a complex trait influenced by numerous environmental and genetic factors and is becoming more common worldwide, most dramatically in urban Asia, but rises in prevalence have also been identified in the US and Europe.
Researchers examined the association of myopia with UVB radiation, serum vitamin D concentrations and vitamin D pathway genetic variants, adjusting for years in education.
The study included a random sample of participants aged 65 years and older.
Of 4,187 participants, 4,166 attended an eye examination including refraction, gave a blood sample and were interviewed by trained fieldworkers using a structured questionnaire.
After exclusion for various factors, the final study group included 371 participants with myopia and 2,797 without.
The researchers found that an increase in UVB exposure at age 14 to 19 years and 20 to 39 years was associated with reduced odds of myopia. The top third of the participants with highest years of education had twice the odds of myopia.
No independent associations between myopia and serum vitamin D3 concentrations or variants in genes associated with vitamin D metabolism were found.
An unexpected finding was that people with highest plasma lutein concentrations were at reduced odds of myopia.
"The association between UVB, education, and myopia remained even after respective adjustment. This suggests that the high rate of myopia associated with educational attainment is not solely mediated by lack of time outdoors," researchers said.
"As the protective effect of time spent outdoors is increasingly used in clinical interventions, a greater understanding of the mechanisms and life stages at which benefit is conferred is warranted," they said.
The study was published in the journal JAMA Ophthalmology.
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