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"Despite the fact that most of our participants were from elite schools, they were not spared the adverse effects of sleep curtailment on their cognitive functions," says June Lo. (Credit: iStockphoto)

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Does a week of little sleep undo lots of studying?

Teenagers who sleep five hours a night for a week experience significant cognitive degradation, new research shows. These findings suggest that staying up to study may backfire for students.

Past research has examined the impact of insufficient sleep on cognitive functions in adolescents. However, in these studies, the extent of sleep restriction was relatively mild.

In a recent experiment, researchers evaluated 56 adolescents, aged 15 to 19 years, as they lived in a boarding school for 14 days during their school holidays. For seven nights, half of the participants received a five-hour sleep opportunity, while the other half had nine hours to sleep—the recommended sleep duration for this age group by the National Sleep Foundation in the United States. They objectively verified participants’ sleep duration using electroencephalogram (EEG) and wrist actigraphy.

In order to gauge their cognitive function, participants underwent cognitive assessments three times a day during the study. Those in the nine-hour sleep group either maintained cognitive performance or showed practice-related gains in tasks requiring arithmetic calculation and symbol decoding.

In contrast, those in the five-hour sleep group showed prominent deterioration of sustained attention, working memory, executive function, alertness, and positive mood. They also showed reduced performance gains (arising from repeated practice) with arithmetic and symbol-decoding.

The researchers discovered that two nights of nine-hour recovery sleep could not fully reverse some of these cognitive deficits.

[Sleepy teens wake at night to check social media]

“Despite the fact that most of our participants were from elite schools, they were not spared the adverse effects of sleep curtailment on their cognitive functions,” says June Lo, lead author of the study and a senior research fellow at Duke-National University of Singapore.

“The present findings should cause students, parents, and educators to reflect on how they use time more efficiently to allow for sufficient nocturnal sleep. This would enable them to realize the benefits of the hard work they put in,” adds Professor Michael Chee, senior author and director of the Centre for Cognitive Neuroscience at Duke-NUS.

Published in the journal SLEEP, this research received support from the National Research Foundation Singapore, the Singapore Ministry of Health, and the Far East Organization.

Source: National University of Singapore

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