NDSU Extension Service - Ramsey County


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How Do We Sleep?

Why Do We Sleep?


                For most of us, life is busy on a good day.  On many other days, we could be described as busy, busy plus add in the upcoming holidays and you might feel like you are in hyper drive.  When life demands much, we find ways to cope and unfortunately many Americans cope by sleeping less.

                Sleep is a fundamental component of good health across the lifespan. It is both restorative and protective. Individuals who do not have adequate sleep are more likely to experience attention and memory difficulties, daytime sleepiness, lack of energy, and are at higher risk of falling or having a traffic accident.

                Inadequate sleep is associated with medical conditions, including heart and lung diseases, high blood pressure, depression, stroke, diabetes, and obesity. Not getting enough sleep can lower metabolic function, compromise immunity, be associated with cancer, increase sensitivity to pain and increase mortality.

                Our nonstop lifestyles, stress, lack of understanding about the health benefits of adequate sleep, and the presence of sleep-related problems are just a few of the reasons children and adults may fail to achieve adequate sleep.

                Sleep has distinct stages that cycle throughout the night in predictable patterns. The brain stays active throughout sleep, and each stage of sleep is linked to a distinctive pattern of electrical activity known as brain waves. Feeling rested and being able to function well depends both on total sleep time and on how much of the various stages of sleep a person gets each night.

                Sleep is divided into two basic types: rapid eye movement (REM) sleep and non-REM sleep (with four different stages). Typically, sleep begins with non-REM sleep, progressing from stage 1 through stage 4. REM sleep begins about 90 minutes after a person falls asleep, and cycles along with non-REM stages throughout the night. Stages 3 and 4 are considered deep sleep, during which it is very difficult to be awaken a person.  Deep sleep is considered the “restorative” part of sleep and is necessary for feeling well rested and energetic during the day.

                Dreams occur during REM sleep. While dreaming, arm and leg muscles are temporarily paralyzed so the sleeper cannot act out dreams. Infants spend half or more of their total sleep time in REM sleep. As a person matures, the percentage of total sleep time spent in REM decreases to about one-fifth of sleep time.

                It is known that REM sleep stimulates the brain regions used in learning and the formation of memories. Studies show, however, that other stages of sleep are also important for brain function.

                How much sleep should we be enjoying? Several factors determine how much sleep is enough.

Healthy adults, when given unlimited opportunity to sleep, will sleep on average between eight and eight and one-half hours. But normal sleep needs range from seven to nine hours.

                Sleep needs also change throughout the lifecycle. As people get older, the pattern of sleep also changes. For example, children spend more time in the deep sleep stages than do adults. Hormonal influences shift adolescents’ biological clock. Teenagers are more likely to go to bed later than younger children and adults, and to sleep later in the morning.

Some evidence suggests that the biological clock shifts in older people, toward going to sleep earlier at.

                The daily need for sleep may be driven, at least in part, by a naturally occurring compound called adenosine. It builds up in the blood while a person is awake. When a person sleeps, the body breaks down the adenosine. This molecule may help the body keep track of lost sleep and trigger sleep when needed. Because of such molecular feedback, a person cannot adapt to getting less sleep than the body requires.

                A lack of sleep puts the body under stress and may trigger the release of more adrenaline, cortisol, and other stress hormones during the day. These hormones contribute to blood pressure not dipping during sleep, thereby increasing the risk for heart disease. Inadequate sleep may also negatively affect the heart and vascular system by the increased production of proteins thought to play a role in heart disease. Some studies find that people who chronically do not get enough sleep have higher blood levels of C-reactive protein, which has been associated with a greater risk of developing hardening of the arteries (atherosclerosis).

                Following is a list of common signs of a sleep disorder. Consult a doctor if you have any of them:

• It takes more than 30 minutes to fall asleep at night.

• You awaken frequently in the night and then have trouble falling back to sleep.

• You awaken too early in the morning.

• You frequently don’t feel well rested despite spending 7-8 hours or more asleep.

• You feel sleepy during the day and fall asleep within 5 minutes if you have an opportunity to nap, or you fall asleep at inappropriate times during the day.

• Your bed partner claims you snore loudly, snort, gasp, or make choking sounds while you sleep. Or your partner notices your breathing stops for short periods. Such occurrences are symptoms of sleep apnea.

• You have creeping, tingling, or crawling feelings in your legs that are relieved by moving or massaging them, especially in the evening and when you try to fall asleep.

• While falling asleep or dozing, you have vivid, dreamlike experiences.

• You have episodes of sudden muscle weakness when you are angry, fearful, or when you laugh.

• You feel as though you cannot move when you first wake up.

• Your bed partner notes that your legs or arms jerk often during sleep.

• You regularly need to use stimulants to stay awake during the day.

                Babies, children, and teens need significantly more sleep than adults to support their rapid mental and physical development. Most parents know that growing kids need good sleep, but many don't know just how many hours kids require, and what the impact can be of missing as little as 30 to 60 minutes of sleep time. One of the reasons it's so hard to know when our kids are getting insufficient sleep is that drowsy children don't necessarily slow down the way we do—they wind up. In fact, sleepiness can look like symptoms of attention deficit-hyperactivity disorder (ADHD).

                How much sleep do you need?




May be appropriate

Not recommended


0-3 months


14 to 17 hours

11 to 13 hours

18 to 19 hours

Less than 11 hours

More than 19 hours


4-11 months


12 to 15 hours

10 to 11 hours

16 to 18 hours

Less than 10 hours

More than 18 hours


1-2 years


11 to 14 hours

9 to 10 hours

15 to 16 hours

Less than 9 hours

More than 16 hours


3-5 years


10 to 13 hours

8 to 9 hours

14 hours

Less than 8 hours

More than 14 hours

School-aged Children

6-13 years


9 to 11 hours

7 to 8 hours

12 hours

Less than 7 hours

More than 12 hours


14-17 years


8 to 10 hours

7 hours

11 hours

Less than 7 hours

More than 11 hours

Young Adults

18-25 years


7 to 9 hours

6 hours

10 to 11 hours

Less than 6 hours

More than 11 hours

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