Boys and girls aged from nine to 15, and who are in the early stages of puberty, are more sensitive to light than are older teens. Even an hour of night-time exposure to screen glare can affect levels of the hormone melatonin, which controls the wake-sleep cycle, and their ability to a get a proper night's sleep.
The brightness of the light affects the level of melatonin that is suppressed, say researchers at Brown University. They tested the effects of light on a group of 38 adolescents in their early teens, and discovered that dim 'mood' lighting supressed melatonin levels by 9 per cent, while normal room lighting suppressed it by 26 per cent, and bright 'supermarket' lights brought levels down by 37 per cent.
Even small amounts of light, such as from tablet and smartphone screens, could be enough to affect sleep, say the researchers. The same could be said for the glare from a television screen.
They advise that young adolescents shouldn't be exposed to any screen glare for at least an hour before they go to bed.
(Source: Journal of Clinical Endocrinology & Metabolism, 2015; jc.2015-2775)