About Sleep

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The Sleep Disorders Center
at Saint Francis

114 Woodland Street
Hartford, CT 06105
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Normal Sleep

Sleep is an active, vital brain function. You require sufficient sleep to function optimally while awake. Your mood, your ability to learn, and your ability to remain alert while awake depend on a good night’s sleep. Sleep enhances other vital body functions including, breathing, heart function, blood circulation, temperature control and normal growth. Normal sleep enhances these functions.

Sleep Structure

Normal sleep has a characteristic structure and progression. Sleep is comprised of two different states: rapid eye movement sleep (REM) and non-REM (NREM) sleep. NREM sleep occurs at sleep onset and quickly deepens. About 90 minutes after sleep onset, rapid eye movement (REM) sleep begins. REM and NREM sleep then alternate for the rest of the night.

The duration of sleep you need depends upon your age, sleep efficiency, and how long you have been awake. This requirement is referred to as the homeostatic sleep need. 

  • Infants sleep most of the day and night. They are awake for brief intervals spread over the entire 24-hour day.
  • During the first two years of life, sleep becomes consolidated into a single major sleep period, supplemented by an afternoon nap.
  • Sleep is most efficient during early adolescence. Ten-year-old children sleep soundly. They do not nap if overnight sleep is sufficient, in most cases between 9 and 10 hours per night. They actually grow more when they are asleep than when they are awake!
  • By age 20, most individuals need about eight hours sleep each night. That sleep requirement changes very little over the rest of an adult lifetime. Even small sleep deprivation over several nights can result in the gradual deterioration of important brain functions, including a reduction in the ability to learn and remember, a diminished social capacity and sense of well-being, and an overall lowering of mood.
  • Sleep efficiency decreases as we age. More time must be allocated to permit sufficient sleep as sleep efficiency decreases.

Biological Clock

Each of us has an internal biological clock which 'runs' by sophisticated operations that take place at the molecular level. One important function of your biological clock is synchronizing your wakeful activity with daylight, and promoting sleep during darkness.

Here’s how it works: during the light of day substances are secreted by a small cluster of cells behind your eyes at the base of your brain. These substances, called neurotransmitters, generate an alerting signal that is projected throughout your entire brain. When the light of day no longer shines, the neurotransmitters are no longer secreted.

Through this synchronization, your biological clock guides your body through regular cycles. One complete cycle lasts a few minutes longer than 24 hours. This cycle is called the circadian alerting rhythm. The word circadian is a combination of two Latin words: circa (near or close to), and dies (day).

To a great extent, the circadian rhythm is independent of external influences. It can, however, be somewhat affected by light, exercise, and social activity. The interaction between our biological alerting clock and our homeostatic need for sleep determines how vigilant we are and how likely we are to fall asleep.

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Poor-Quality Sleep

A sufficient duration of normal sleep during each 24-hour cycle promotes alertness and prepares the body for the challenges of the day.

Abnormal sleep

Abnormal sleep is nonrestorative, providing insufficient rest for the body. It’s usually caused by disturbances, called dysomnias, and the result is excessive sleepiness and fatigue during the day. Sometimes sleep behaviors or physiological changes arise during sleep. These can cause partial or complete awakening, called parasomnia. 

The loss of alertness as a result of abnormal or insufficient sleep can result in further problems for the one suffering lack of sleep, as well as for others. As one example, the risk of automobile accidents increases among drivers with insufficient normal sleep.


Difficulty falling asleep, frequent awakenings during sleep, and being unable to return to sleep, are all manifestations of insomnia. Mood disorder such as depression is a common cause.

Normal sleep can also be disrupted by any of the following:

  • Medical conditions such as heart disease, lung disease, acid reflux, and arthritis
  • Self-administered drugs such as caffeine, alcohol, and nicotine
  • Medications, including corticosteroids, beta-blockers, and many antidepressants

Circadian Sleep Disorders

Circadian sleep disorders develop whenever sleep behavior is poorly coordinated with the body's internal cycle. This is a common problem for shift workers, including police, firefighters, medical personnel, and military personnel. One very common circadian sleep disorder is well-known to those traveling cross country or internationally; it’s referred to as jet lag.  

Night owls - those who function best during the evening and go to bed late – tend to develop two types of sleep problems:

  1. Difficulty falling asleep
  2. The need to sleep later

Night owls may try to compensate by attempting to sleep earlier than their usual bedtime, but are often defeated because their “biological alerting mechanism” is still very active.

Parasomnias - Abnormal behavior during sleep

The transition between sleep and being fully awakened is notably unstable. For most, this transition is uneventful. But some experience bizarre behaviors or unpleasant experiences, called parasomnias, during this transition.

Parasomnias may include:

  • Sleepwalking
  • Sleep talking
  • Enuresis
  • Night terrors
  • Confusional arousals

Those manifesting a parasomnia may seem possessed, or indifferent to those trying to interact with them. Parasomnia behaviors can be quite complex, such as opening a door or eating a snack. They’re usually followed by a return to sleep with no later memory of the event.

Sometimes parasomnias persist from childhood into adulthood. Parasomnias may also develop in adulthood as a result of sleep deprivation, medication, substance abuse, or neurological disorders.

One parasomnia that usually develops in older adults is REM behavior disorder (RBD). This parasomnia is characterized by the physical acting out of dreams. Those manifesting RBD may lunge out of bed, or strike their bed partner. A small percentage of those with RBD later develop a chronic neurological condition. RBD episodes can be controlled with medication.

Care for Parasomnia

Alert as they may seem, it’s a good idea to reduce the risk of injury to sleepwalkers by protecting them from dangerous obstacles and stairways. Those forcibly awakened from a parasomnia event may be initially disoriented, and may struggle violently until fully awake.

Parasomnias can usually be minimized by returning to a regular bedtime routine and a sufficient duration of normal sleep. In some cases, medication may be needed to stabilize sleep.

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