Why do babies sleep so much?

Early infant sleep is often broken up into so many pieces that it never seems restful, but that doesn’t mean there isn’t a lot of it. Even when babies are sleeping up to 20 hours a day, they’re still hard at work. Research suggests that, even when babies look like they’re sleeping peacefully, there’s a lot more going on beneath the surface than meets the eye.


In the beginning of a baby’s life, it might seem like there just isn’t time for learning, between all of the sleeping and all of the growing Baby does, but their education starts early, and sleep plays an important part in it. In those first few months of life, newborns sleep in fragmented bursts with frequent waking. This pattern of sleep is thought to be especially good for early learning for a few different reasons. 

In the first place, the shorter-lasting patterns, which lead to a shallower sleep, may help the brain mature. It can also help memories and learning get consolidated and stored in that fast-growing brain. More than that, even when they’re asleep, infants are processing and learning from the things they’ve done and seen when they were awake. 

For example, a 2006 study of the way 15-month-olds learn language showed that children who took a nap after hearing words in a new language were more likely not just to memorize those words, but to know how to use them, or use them creatively. A follow-up study then looked at how 15-month-olds retained the information 24 hours later, and the results suggested that sleep is a key component of committing something to long-term memory.


It may sound obvious to say that well-rested babies are happier and more social than babies who have a harder time getting enough rest, but there is actually research to back this seemingly-obvious fact. A 2008 study concluded that, of the babies who were surveyed, at ages 3, 6 and 11 months, the ones who slept longer and in more regular intervals tend to have more approachable personalities, as well as greater adaptability, and that this could last throughout babyhood.

In addition, a 1999 study showed that young toddlers, ages 14 to 16 months old, who slept poorly tended to become more distressed by mildly stressful situations than well-rested babies do.


The effect of sleep on growth is hard to pin down, since there’s no way to tell how much a baby would have grown under different circumstances. However, sleep has been linked with the body’s production of human growth hormone. Beyond that, several studies, including a 2009 study of infant growth in the first 6 months of life, drew a connection between shortened or fragmented sleep and childhood obesity.

There’s a limit to the amount of research available on the effect infant growth has on mood or learning, but the connections are there. It may be a cliche, but it’s also true – in the end, Baby sleeps so much because they are a growing child!

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