A new study finds that midday naps boost learning in preschoolers, suggesting if policymakers eliminate classroom naps for young children to allow more time for educational activity, it could backfire.
Researchers from the University of Massachusetts Amherst write about their findings in the current online issue of the Proceedings of the National Academy of Sciences, PNAS.
They explain in their study background that despite the fact midday naps are common in early childhood, we know little about their structure and function.
However, we do know that sleep boosts memory in young adults, so perhaps naps do the same for young children.
Pressure to eliminate midday naps
Meanwhile, numbers of publicly funded preschools and enrollments in them are increasing in the US, driven by copious studies that show the long-term health and educational benefits of early education.
And parents and administrators are debating whether to eliminate daytime naps in the classroom to make way for more curriculum activity.
A possible argument in favor is that since children begin to drop their daytime sleep in early childhood anyway, these classroom naps cannot be that important - perhaps they only contain light sleep stages and do not contribute much to memory and learning by this age.
New study shows naps have learning value
But this new study fills a much-neglected gap in scientific understanding about the value of daytime naps in young children.
Based on observations and measurements of more than 40 preschool children, research psychologist Dr. Rebecca Spencer, with students Kasey Duclos and Laura Kurdziel, suggest daytime naps are important for memory consolidation and early learning.
"Here we show evidence that classroom naps support learning in preschool children by enhancing memories acquired earlier in the day compared with equivalent intervals spent awake."
They found that the children who appear to benefit the most are those who nap habitually, regardless of age.
Also, subsequent nighttime sleep does not help recover performance losses in nap-deprived youngsters.
Learning losses greater in nap-deprived preschoolers
The researchers found that children who did not have a regular daytime nap forgot more of what they learned that day, compared with days when they did have a nap.
For their study, the researchers taught the children - who were attending six preschools across western Massachusetts - a visual-spatial memory game in the mornings.
In the morning game, the children saw a grid of pictures and then had to remember where each one was located.
The researchers then tested the children's memory again in the afternoon under two conditions.
In one condition, the children were encouraged to have their regular daytime nap in the classroom. The naps lasted about 75 minutes on average. In the other condition, the children were kept awake for the equivalent amount of time.
The researchers tested the children's ability to remember the picture locations after the nap and wake periods, and also the next day, to see whether having a night's sleep affected their performance.
The results showed that after a night's sleep, nap-deprived children forgot significantly more picture locations, compared with when they did take a nap.
The authors explain that while the children performed about the same in both conditions, when tested just after learning the locations, their ability to remember the picture locations was significantly better the next day if they had taken a nap after learning the previous day.
"That means that when they miss a nap, the child cannot recover this benefit of sleep with their overnight sleep. It seems that there is an additional benefit of having the sleep occur in close proximity to the learning," they write.
Sleep spindle density correlated with memory benefit
In a separate experiment, the researchers invited another 14 preschoolers to a sleep lab so they could monitor their biophysiological changes during their daytime naps using a polysomnograph.
They found correlations between sleep spindle density - a burst of brain activity that is linked to integrating new information - and the memory benefit of sleep during the nap.
Dr. Spencer says they hope their findings will help policymakers and administrators make "educated decisions regarding the nap opportunities in the classrooms."
"Children should not only be given the opportunity, they should be encouraged to sleep by creating an environment which supports sleep," she urges.
The researchers suggest preschools should have policies on napping and call for more studies to look at how to protect and encourage naps to help young children boost their learning.
Funds from the National Heart, Lung and Blood Institute at the NIH, and a UMass Amherst college grant helped finance the study.
Another US study published in 2012 suggested that chronic missed naps could put toddlers at risk for mood-related problems later in life.