Why do some preschoolers stop taking afternoon naps at age 3, while others don’t until they are 4 or 5 years old?

It’s an issue that many parents, no doubt, wonder about, and one that a sleep scientist at the University of Massachusetts Amherst has been thinking about for years. Lead author Rebecca Spencer offers a novel theory regarding why and when young infants transition out of naps in a paper released today, in a special sleep issue of Proceedings of the National Academy of Sciences. The brain is more important than age.

According to Spencer, professor of psychological and brain sciences, and co-author Tracy Riggins, a University of Maryland child psychologist who specializes in memory development, “this overarching theory is based on data that we’ve published over the past couple of years; it’s about putting the pieces together.”

“Collectively, we provide support for a relation between nap transitions and underlying memory and brain development. We’re saying this is a critical time of development in the brain and sleep has something to do with it.”

The unique idea links bioregulatory mechanisms governing nap transitions, focusing on the hippocampus – the memory part of the brain, and supports the practice of allowing all preschoolers and prekindergarteners the option to nap. Spencer points out that young children giving up their regular naps may appear counterintuitive.

“When little kids are napping, they consolidate emotional and declarative memories, so then you ask yourself, when this is such an important time of learning, why would they transition out of napping if napping is helping learning? Why not just keep napping?”

Previous research by Spencer and Riggins revealed “a difference in the development of the hippocampus for kids who nap and those who have transitioned out of naps,” Spencer adds.

The hippocampus is where memories are temporarily stored before being transferred to the cortex for long-term storage. The purpose of the naps, according to Spencer, is to process memories. Children endure increased “sleep pressure” when their developing hippocampus reaches the maximum number of memories that can be kept without “interference” or forgetting. To evaluate the accumulation of homeostatic sleep pressure, researchers use EEG slow-wave activity, a neurobiological signal in brain waves collected during sleep.

By allowing memories to flow to the cortex during sleep, the hippocampus has more room to retain information. Spencer says that the hippocampus is like a bucket whose size changes as it grows.

“When the hippocampus is inefficient, it’s like having a small bucket,” she adds. “Your bucket is going to fill up faster and overflow, and some memories will spill out and be forgotten. That’s what we think happens with the kids that are still napping. Their hippocampus is less mature, and they need to empty that bucket more frequently.”

When the hippocampus is fully developed, children can stop taking naps since their hippocampus has matured to the point where their “bucket” will not overflow. The researchers claim that memories can be stored until the end of the day, when information can be transferred from the hippocampus to the cortex during nighttime sleep.

According to Spencer, mounting research emphasizes how crucial it is to give all young children the chance to take naps. “Some of them still need it; others may not need it but if they take it, we know that it’s going to benefit their learning, and we know that learning is what underlies early education.” 

To move the theory forward, researchers need to keep track of children over time to study their sleep physiology, structural and functional development, and how their memories change between naps.

More scientific proof “would help parents and providers appreciate that nap transitions cannot be determined by age, and the opportunity to nap should be protected for those that need it.”

In the long run, according to Spencer, researchers might be able to create a cognitive test of memory, perhaps giving children a short assignment to see whether they’ve reached the point where they require frequent naps.

But for the time being, the data seem consistent with the significance of naps in early children’s development. Spencer warns that abrupt awakenings “could lead to suboptimal learning and memory.”

Additionally, the new framework created by the researchers “can be used to evaluate multiple untested predictions from the field of sleep science and, ultimately, yield science-based guidelines and policies regarding napping in childcare and early education settings.”

Source: 10.1073/pnas.2123415119

Image Credit: Getty

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