SINGAPORE: Napping as part of a daily schedule “significantly improves learning and memory” for teenagers, National University of Singapore (NUS) researchers have found.
A study done on participants aged between 15 and 19 showed that napping could be beneficial, regardless of whether the participants had sufficient sleep in a 24-hour period.
Over two weeks, a shorter period of sleep at night and an afternoon nap led to “significant gains” in afternoon memory performance, NUS said in a press release on Wednesday (Mar 17).
“Critically, the reduced nocturnal sleep associated with this ‘split sleep schedule’ did not impair learning in the morning,” the university said.
“Analysis of EEG recordings of brain activity during sleep suggested that the additional opportunity to engage in slow-wave sleep during the nap could have contributed to this benefit.”
The university said that while the memory benefits of daytime naps are well-known, naps have typically been studied as a one-off supplement to nocturnal sleep, rather than as part of a regular sleep schedule.
As many students in this age group do not sleep enough, the researchers wanted to investigate how different ways of apportioning sleep across 24 hours could affect learning, the university added.
RESEARCH DONE WITH FOUR GROUPS
The researchers conducted two 15-day studies with 112 participants in a boarding school. The participants were divided into four groups.
The first factor examined was whether students had at least eight hours sleep and therefore sufficient sleep, or whether they had six-and-a-half hours, the number of hours of sleep “restricted to a level common in the local adolescent population”.
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The second factor examined was whether sleep was continuous at night, or split between sleep at night and a one-and-a-half-hour nap in the afternoon.
Their long-term memory was assessed in two ways. The first was a picture encoding task, which involved looking at 160 images. All 160 images were presented again, but with another 80 randomly added to the mix. The students were asked to indicate their confidence that images were old or new on a five-point scale.
The second involved an “educationally realistic factual knowledge task” that involved learning facts about several species of amphibians.
Splitting sleep enhanced afternoon performances for both memory tasks, regardless of whether the participants were sleep restricted or well rested. Sleep monitoring with polysomnography showed a reduced build-up of sleep pressure at night under the split sleep schedule.
The researchers suggested that slow-wave sleep during the nap may downscale synapses that are crucial for learning, refreshing them to more effectively encode new information afterwards.
"Alternatively, it could be that memory reactivation during the nap reorganised information learned in the morning, so that there is effectively more room for new information to be learnt in the afternoon," said NUS.
“Irrespective of the actual mechanism(s), the findings suggest that regular nap opportunities in schools may provide sufficient sleep and improve learning outcomes."
The study’s principal investigator Professor Michael Chee, director of the Centre for Sleep and Cognition at the Yong Loo Lin School of Medicine, added: "Demonstrating the benefit of a multi-night split sleep schedule on memory in two different tasks in the same students is a unique finding and should persuade educators to make provisions for napping."
Dr James Cousins and Dr Ruth Leong were “major contributors” to the study, NUS said. The study was funded by the National Medical Research Council, the National Research Foundation and the Far East and Lee Foundations.