NEW YORK: Messaging in the dark affects sleep, health and performance in school, says a study.
Students who text for longer durations in the dark sleep only for a few hours and thus remain sleepy during the day as compared to those who stopped messaging when they went to bed, researchers from Rutgers University in New Jersey, US, said.
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Texting before lights out did not affect academic performance, the study showed.
Although females reportedly messaged more and experienced daytime sleepiness, they had better academic performance than males. Researchers attributed this to the fact that the girls texted primarily before turning off the light.
"We need to be aware that teenagers are using electronic devices excessively and have a unique physiology," said Xue Ming, a professor at the Rutgers University.
Adolescents should be getting eight and a half hours of sleep at night, the researchers said, adding that deficiency in sleep can affect their Rapid Eye Movement (REM) -- the period during sleep most important to learning, memory consolidation and social adjustment in adolescents.
When sleep is delayed but rising time is not, REM sleep will be cut short, which can affect learning and memory, the researchers explained.
The effects of "blue light" emitted from smartphones and tablets are intensified when viewed in a dark room.
This short wavelength light can have a strong impact on daytime sleepiness symptoms since it can delay melatonin release -- a hormone that helps control sleep, making it more difficult to fall asleep - even when seen through closed eyelids, researchers noted in the study published in the Journal of Child Neurology.
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To conduct her study, Ming distributed surveys to three New Jersey high schools - a suburban, an urban public school and a private school - and evaluated the 1,537 responses contrasting grades, sexes, messaging duration and whether the texting occurred before or after lights out.