Small children and babies who sleep with the light on are more likely to grow up shortsighted than children who sleep in the dark, a team of US researchers reported last week.
A study of 479 children aged between 2 and 16 years shows that children who sleep with a room light on before the age of 2 are five times more likely be shortsighted than children who sleep in the dark. Night lights were also linked to short sight but not as strongly as full overhead lighting.
“Our findings suggest that the absence of a nightly period of full darkness in early childhood may be an important risk factor in the development of nearsightedness,” said Richard Stone, senior investigator and professor of ophthalmology at the Scheie Eye Institute in Pennsylvania.
“The study does not establish that night time lighting during early childhood is a direct cause of myopia … still, it would seem advisable for infants and young children to sleep at night without artificial lighting in the bedroom until further research can evaluate all the implications of our results.”
The findings, published in Nature (1999;399:113), were based on a survey of children attending an ophthalmology clinic at a US tertiary referral centre.
Parents filled in a questionnaire exploring the child’s current and past exposure to light, including lighting at home, at day care, and at school. Parents were also asked whether their child wore sunglasses.
A clear and dose dependent association between night time lighting in early childhood and short sight emerged. One tenth of children who slept in darkness had myopia compared with 34%of children who slept with a night light on and 55%of children who slept with a full light on. The results are statistically significant at the 5%level and are adjusted for age.
Critically, the researchers found no link between current night time lighting and sight problems.
The study was done against a background of an increasing prevalence of myopia.
The researchers warned that their results were not conclusive and should be treated with caution until bigger and better prospective studies are done. For example, they were unable to rule out confounding by parental shortsightedness. Shortsighted parents may be more likely to light their children’s bedrooms and are certainly more likely to have shortsighted children.
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JANE VOLLERS/PHOTONICA
Should young children sleep without artificial lighting?