New York: Parents, take note! A new study has found that night-time texting habits of teenagers may be to blame for their falling grades and increased yawning in school.
Researchers from Rutgers University in US distributed survey to three New Jersey high schools and evaluated the 1,537 responses contrasting grades, sexes, messaging duration and whether the texting occurred before or after lights out.
They found that students who turned off their devices or who messaged for less than 30 minutes after lights out performed significantly better in school than those who messaged for more than 30 minutes after lights out.
Students who texted longer in the dark also slept fewer hours and were sleepier during the day than those who stopped messaging when they went to bed. Texting before lights out did not affect academic performance, the study found.
"Students tend to go to sleep late and get up late. When we go against that natural rhythm, students become less efficient," said Xue Ming from Rutgers University.
Although females reported more messaging overall and more daytime sleepiness, they had better academic performance than males.
"I attribute this to the fact that the girls texted primarily before turning off the light," Ms Ming said.
"The effects of 'blue light' emitted from smartphones and tablets are intensified when viewed in a dark room," she said.
This short wavelength light can have a strong impact on daytime sleepiness symptoms since it can delay melatonin release, making it more difficult to fall asleep - even when seen through closed eyelids, she said.
"When we turn the lights off, it should be to make a gradual transition from wakefulness to sleep. If a person keeps getting text messages with alerts and light emission, that also can disrupt his circadian rhythm," Ms Ming said.
"Rapid Eye Movement (REM) sleep is the period during sleep most important to learning, memory consolidation and social adjustment in adolescents. When falling asleep is delayed but rising time is not, REM sleep will be cut short, which can affect learning and memory," she said.
The findings were published in the Journal of Child Neurology.