Published on Psychology Today
When I get up in the morning, the first thing I think about is when I can go back to sleep. Sounds a bit depressing, but we do sleep for 1/3 of our lives. When we haven’t gotten enough sleep, we yearn for more, and in fact, our bodies try to recoup it. This suggests that sleep is important for us in some way, but how?
First of all, do we actually need sleep? Yes and no. Not all animals sleep. But some animals will die if they don’t get it. Studies of sleep deprivation in rats and flies shows that enough sleep deprivation could result in death. For humans, not getting enough sleep could lead to problems functioning with daily tasks, mood disruptions, and long-term health problems. Why? Because our brains need sleep to rejuvenate, and most importantly, it helps us consolidate the memories that we made that day.
This is especially important for infants and young children whose brains are still developing in the first years of life. Newborns, for example, sleep up to 20 hours a day. As they get older, they spend more and more time awake, but infants and young children still take regular naps until between 2 and 4 years of age.
One classic study with newborns showed that sleep is especially important for the development of the immature visual system in the first few months of life. REM sleep—which stands for rapid eye movement—is particularly important for young infants. Scientists believe that brain activity during REM sleep (which is the stage of sleep when the brain is most active) helps stimulate the visual system which doesn’t get a lot of stimulation in the first few months of life. In one classic study, researchers showed newborn infants one of two images while they were awake. Half the infants saw a boring gray square, while the other half saw a square with lots of black and white lines (which is as interesting as it gets when you’re a few weeks old). They found that the group of infants who saw the more interesting square engaged in less REM sleep afterwards than newborns who saw the boring old gray one. The researchers concluded that the newborns who saw the gray square needed more REM sleep from the lack of visual stimulation that they received when they were awake—stimulation that the other group of newborns got by looking at the more interesting pattern (Boismeyer, 1977).
Besides stimulation to the visual system, sleep also allows us to consolidate, or store our memories. It also helps us learn. Several studies have shown that napping following learning in infants as young as 3 months of age can help solidify memories of the things they just saw. This benefit extends to the preschool age, and preschool children who get more REM sleep remember better than children who get less. In fact, delaying sleep after learning may actually inhibit children’s ability to recover those memories later on (Mason et al., 2021).
So if napping is so important for brain development, why then do children stop napping at some point? Researchers theorize that it has something to do with the development of the hippocampus—a peanut shaped brain structure that is deep in our temporal lobe—which plays a major role in learning and memory. Importantly, the hippocampus is not fully developed when we are born and isn’t even fully functional until the ages of 18 to 24 months, which is why remembering anything before that period is difficult or even impossible. The hippocampus continues to undergo a lot of change between infancy and the preschool years, and researchers believe that napping is particularly important during this time to allow the immature hippocampus to consolidate a smaller number of memories. In other words, when the hippocampus is still immature, it has to work harder to consolidate the day’s memories, and napping helps lessen that load (Spencer & Riggins, 2022). Once hippocampus is fully developed, napping is less necessary, which is why kids tend to drop their final nap around preschool age (Ganesh et al.,2024). Consistent with this theory, several studies have shown that kids who are still napping regularly forget things more quickly than kids who are done with naps, suggesting a more mature hippocampus for non-nappers (Ganesh et al 2024)
Clearly napping is an important thing for infants and young children. But what about older kids and adults? It turns out that napping isn’t just for babies. Adolescents need less sleep than kids do, but napping during the day has been shown to benefit adolescents, who are often sleep deprived (Ji et al., 2019). For older adults, daytime napping has shown benefits for daytime sleepiness, overall speed and accuracy of performance on motor tasks, and on learning and memory. On top of that, it does not necessarily have a negative impact on nighttime sleep (Souabni et al., 2022) The same seems to be true for napping in young and middle-aged adults, demonstrating benefits for mood, alertness, and performance on a number of cognitive tasks (Milner et al., 2008, 2009)
So far it sounds like we should all stop reading this and just take a nap instead. But not so fast: Not all studies agree that there is a benefit for napping past childhood. Instead, it seems to depend on when you nap, and for how long. One study reported, for example, that taking naps later in the day disrupts nighttime sleep (Mograss et al. 2022) while naps during the afternoon slug (between 1 and 3pm) can be beneficial (Milner et al., 2009). There is also some evidence that short naps (20-30 min) are more beneficial than long naps (> 1 hour) (Milner et al., 2009). In fact, the effectiveness of a nap for adults can depend on a lot of factors, such as the need for sleep, the stability of one’s sleep schedule, quality of sleep the night before, and how alert you are during the day.
The take home message here is that infants and children need to nap, and while adults don’t need it like kids do, a little afternoon snooze isn’t such a bad thing. If you want to make your nap count, limit the nap to under an hour, and make sure to nap early in the day as not to disrupt any nighttime sleep routines. You could even try to nap right after you’ve learned something new so that you could potentially remember it better. After all, napping isn’t just for babies.
Photo by rachel CALAMUSA/Wikimedia Commons
References
Boismeyer, J. D. (1977). Visual stimulation and wake-up sleep behavior in human neonates. Developmental Psychobiology, 10, 219-227.
Ganesh, D. B., Pandey, M., Riggins, T., Spencer, R. M., Tiwari, R., Wehland, M., & Leikin, S. (2024). Where did naptime go? Why older kids do not nap at school. doi: 10.3389/frym.2023.1224593
Ji, X., Li, J., & Liu, J. (2019). The relationship between midday napping and neurocognitive function in early adolescents. Behavioral sleep medicine, 17(5), 537-551.
Mason, G. M., Lokhandwala, S., Riggins, T., & Spencer, R. M. (2021). Sleep and human cognitive development. Sleep medicine reviews, 57, 101472.
Milner, C. E., & Cote, K. A. (2008). A dose-response investigation of the benefits of napping in healthy young, middle-aged and older adults. Sleep and Biological Rhythms, 6, 2-15.
Milner, C. E., & Cote, K. A. (2009). Benefits of napping in healthy adults: impact of nap length, time of day, age, and experience with napping. Journal of sleep research, 18(2), 272-281.
Mograss, M., Abi‐Jaoude, J., Frimpong, E., Chalati, D., Moretto, U., Tarelli, L., ... & Dang‐Vu, T. T. (2022). The effects of napping on night‐time sleep in healthy young adults. Journal of sleep research, 31(5), e13578.
Souabni, M., Souabni, M. J., Hammouda, O., Romdhani, M., Trabelsi, K., Ammar, A., & Driss, T. (2022). Benefits and risks of napping in older adults: A systematic review. Frontiers in aging neuroscience, 14, 1000707.
Spencer, R. M., & Riggins, T. (2022). Contributions of memory and brain development to the bioregulation of naps and nap transitions in early childhood. Proceedings of the National Academy of Sciences, 119(44), e2123415119.
Comments