Natalie is a teacher and holds an MA in English Education and is in progress on her PhD in psychology.
Jerry is a new father, and he just wants to get some sleep, but his daughter Amy won't let him. Every time he goes to sleep for a few hours, Amy wakes him up with her crying. He feels exhausted and begs Amy to go back to sleep and let him get a few more winks, but she keeps waking him up.
Any parent remembers how tiring it can be to deal with a newborn who doesn't sleep through the night. But eventually, even the most finicky babies will settle into some sort of sleep schedule. This is a normal part of development, or the way people grow and change throughout life.
Let's look closer at two key components of sleep development: the volume of sleep and the type of sleep in infants.
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Volume of Sleep
Though it doesn't seem like it to Jerry, Amy is sleeping a lot. She, like other newborns, gets an average of about 16 hours of sleep per day. That's way more than most adults! In fact, it's the exact opposite of most adults: Amy and other newborns are asleep for an average of 16 hours a day and awake for an average of 8 hours a day. Adults, on the other hand, need about 8 hours of sleep, which allows them to be awake for about 16 hours every day.
Newborns need the extra sleep. Their bodies are growing and changing so rapidly that sleep allows them to shut off and let their bodies repair. Sleep is when most physical growth occurs, so babies will naturally sleep a lot. Amy's little body knows that she needs to grow, and so it shuts down and lets her sleep for the majority of a 24-hour day.
But sleep volume, like other types of growth, changes as Amy ages. By age two, most babies are averaging only 9-12 hours of sleep per day. As their growth slows down, they need less sleep.
Type of Sleep
So if Amy is sleeping 16 hours a day, why does Jerry feel like she's not letting him get enough sleep?
Sleep volume, or the number of hours spent asleep, is only one factor in sleep development. Another key component of sleep development is how a person sleeps. Newborns, like Amy, engage in polyphasic sleep, or sleeping multiple times during a 24-hour period. Amy and other newborns have 6 or 7 periods of sleep per day. That means that, though she's sleeping 16 hours a day, she's not sleeping very long at any given time.
On the other hand, Jerry and most adults engage in monophasic sleep, which involves one long sleep period per day. 'Poly' means 'many,' and 'mono' means 'one,' so you can remember that 'polyphasic' means 'many phases' and 'monophasic' means 'one phase.'
Because Jerry is used to monophasic sleep, and Amy is interrupting his one phase of sleep, it feels like he can't get very much sleep. During the night, when he is used to sleeping, Amy keeps waking him up. And during the day, when Amy takes lots of naps, Jerry isn't used to sleeping and can't take as many or as long a nap as she does.
Eventually, of course, Amy will move from polyphasic to monophasic sleep. Partly, this shift is due to natural physical development, but part of it is probably environmental as well. Jerry encourages Amy to sleep through the night so that he can, which (combined with her natural development) helps her move into monophasic sleep.
Development is the way that people change and grow throughout life. Sleep development is a product of two changes that occur in infancy: the shift from needing a higher to a lower volume of sleep and the shift from polyphasic sleep to monophasic sleep, or from sleeping many times each day to only sleeping once per day.
Following this lesson, you should be able to:
- Describe the importance of sleep to development
- Explain an infant's need for sleep in terms of volume of sleep and the type of sleep
- Differentiate between polyphasic and monophasic sleep
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Sleep-Wake Patterns in the First Two Years
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