Sleep is not as passive as it initially appears. In fact, scientists are still uncertain about exactly what happens to the brain when a person is asleep. This downtime may have diverse and essential roles in growth and development, the formation of memory, the acquisition of new skills, or the process of the brain “downsizing” itself by getting rid of unnecessary connections between nerves. However, one thing is certain: Without quality sleep, nobody can function effectively for very long.

Stages of Sleep

There are two general types of sleep — the one involved with dreaming and the other without. The type of sleep that occurs while dreaming is described as REM (rapid eye movement) sleep, and the other is called non-REM sleep. REM sleep is named because during this type of sleep, the eyes dart rapidly back and forth, even though the eyelids are shut. Dreams occur during this type of sleep, and the brain is almost as active as it is in waking states. During non-REM sleep, the brain is calm. Ironically, it is during non-REM sleep when many of the problems associated with sleep, such as bed-wetting and sleepwalking, occur.

Throughout the night, the brain goes through many cycles of REM and non-REM sleep, alternating between the two types. For infants, the cycles rotate much faster, in approximately sixty-minute intervals. As the child grows older, the cycles slow down, turning over every ninety minutes or so. It is during this transition from REM to non-REM sleep that a baby is most likely to wake up. Due to the shorter cycles, infants wake up more often at night than older children.

How Much Sleep Is Enough?

The total number of hours of sleep varies depending on the age of the child and individual differences. Just as body size and appetite differ significantly from one person to the next, the requirement for sleep also varies widely. While there is no absolute “right” amount of sleep for everyone, there are general patterns for different age groups.

It is obvious that babies generally require more sleep than older children. Newborns typically go through short two-to three-hour cycles of feeding, playing, and sleeping throughout the day. Their sleep pattern is not dictated by the sunlight at all but rather by their internal rhythm. If you add up all the hours of naps, an average newborn sleeps about fifteen to eighteen hours in a twenty-four-hour period.

As your baby becomes older, the total amount of sleep decreases, and the sleep cycle becomes more in tune with a circadian rhythm (that is, the pattern established by sunlight). By six months, most babies spend most of the night sleeping and spend longer periods of time awake during the daytime. Frequent daytime naps are essential to provide enough sleep for these babies.

By the time your child is a toddler (one to three years of age), he needs even less sleep and spends the majority of the day awake and active. Children of this age typically require twelve to fourteen hours of sleep in a twenty-four-hour period. Many of them only nap once or twice a day, spending about an hour or two asleep for each nap.

Once again, it is important to remember that there is a lot of individual variability when it comes to sleep. Many parents worry that there might be something wrong with their child because their toddler does not take naps during the day at all. As long as the child appears well rested and alert during the day and gets quality sleep time at night, there is no need to be concerned about sleep deprivation.

As your child enters adolescence, the requirement for sleep is more similar to that of an adult. However, nine to ten hours of sleep is typically necessary to ensure that your teenager is refreshed in the morning and alert enough to take on the academic tasks at school. Unfortunately, as your teenager becomes more independent, it becomes more difficult to regulate bedtime and the daytime schedule. According to many studies, most adolescents spend their days sleep-deprived — just like most adults.

How can you be sure that your child is sleeping enough? As a good rule of thumb, if your child does not wake up cranky and does not doze off during times when he is expected to be awake, he is getting enough sleep at night.