PNAS Sleep Special: It is the brain, not age, that determines children's naps

Why do some 4- and 5-year-olds still nap punctually every afternoon, while others start giving up habitual naps at age 3?

There's no doubt that this is something that many parents are pondering, and one that sleep scientists at the University of Massachusetts Amherst have been pondering for years
.
Now, in a paper published Monday Oct.
24 in a special issue of PNAS sleep, lead author Rebecca Spencer describes a new theory
about why and when young children stop napping.
It's not about age, it's about
the brain.

"This main theory is based on data we've published over the past few years, and overall, we provide support
for the relationship between nap transitions and underlying memory and brain development.
" We think this is a critical period for brain development and is related to
sleep.
”

This novel theory supports the practice of providing napping opportunities for all preschoolers and kindergarten preschoolers, and it links the bioregulatory mechanisms of napping transitions, focusing on the hippocampus, the memory region
of the brain.
Getting the little ones to give up their habitual naps may seem counterintuitive
.
"When the little ones are napping, they consolidate emotional and declarative memories, so you ask yourself, when this is an important time to learn, why would they give up napping if napping helps learning? Why don't you keep napping?"

Previous research has shown that "napping children and non-napping children differ in the development of the hippocampus," Spencer said
.

The hippocampus is the short-term location
of memories before they are transferred to long-term storage in the cerebral cortex.
Spencer explains, "Naps are about processing memories
.
" When young children's immature hippocampus reaches the limit of memory storage that is not "disturbed" or forgotten, children experience greater "sleep stress"
.
The researchers measured the buildup
of homeostatic sleep stress by looking at EEG slow-wave activity, a neurobiological marker in brain waves recorded during sleep.

Napping allows memories to transfer to the cerebral cortex, making room
for more information to be stored in the hippocampus.
Spencer likens the developing hippocampus to a bucket
of varying sizes.

"When the hippocampus is inefficient, it's like a barrel
," she said.
Your bucket will fill up and overflow faster, and some memories will overflow and be forgotten
.
We think this happens to children who are still napping
.
Their hippocampus is not mature enough to empty that barrel
more often.
”

When the hippocampus is more mature, children can stop napping because their hippocampus has matured to a point where their "bucket" does not overflow
.
Researchers believe they can save memories to the end of the day, and nighttime sleep can transmit information from the hippocampus to the
cerebral cortex.

Spencer said the growing body of evidence highlights the importance of
providing napping opportunities for all young children.
"Some people still need it; Others may not need it, but if they attend, we know it will benefit their learning, and we know that learning is the foundation of
early education.
”

To advance this theory, the next step is longitudinal studies with long-term follow-up of children to assess the development of sleep physiology, structure, and function, as well as memory changes
during nap transitions.

Additional scientific evidence "will help parents and service providers recognize that the transition to napping cannot be determined by age and should protect access for those who need it
.
" ”

In the long run, researchers may be able to develop a cognitive measure of memory, perhaps giving children a simple task to determine whether they have crossed the threshold
of needing regular naps.

For now, however, there is evidence to support the important role
that napping plays in young children's development.
Spencer said being forced to transition from napping "can lead to suboptimal learning and memory.
"

In addition, the new framework developed by the researchers "can be used to evaluate multiple unvalidated predictions from the field of sleep science and ultimately produce science-based guidelines and policies regarding napping
in childcare and early education settings.
" ”

Rebecca M.
C.
Spencer, Tracy Riggins.
Contributions of memory and brain development to the bioregulation of naps and nap transitions in early childhood.
Proceedings of the National Academy of Sciences, 2022; 119 (44)