Antihistamine A type of chemical present in many cold and allergy medicines,
and some nonprescription sleep medicines, for example diphenhydramine and doxylamine. When taken at night as sleep aids, antihistamine-containing
medicines may result in daytime drowsiness.
Barbiturates Sedating medications that were used as sleep aids years
ago but are rarely prescribed for insomnia today, due to their overall safety risks.
Benzodiazepines A class of medications often prescribed for sleep problems or anxiety.
This class includes both long-acting medicines (which can linger in the body and
potentially cause daytime drowsiness) and short-acting medicines (which do not stay
in the bloodstream as long).
See Non-benzodiazepines.
Bruxism See Teeth Grinding.
Circadian Rhythms These biological rhythms include the
"internal clock,"
which influences when, how much, and how well people sleep.
Deep (slow-wave) Sleep Also called delta sleep, this type of sleep
occurs in stages 3 and 4 of NREM sleep.
Half-life Half-life refers to how long a drug stays in the body after
it has been taken.
Hypnotics Hypnotics are medications that cause sleep or partial loss
of consciousness.
Insomnia Sleep problems characterized by difficulty falling asleep,
difficulty staying asleep, or waking up earlier than desired. Insomnia results
in getting up in the morning feeling unrested and experiencing drowsiness during
the day.
Internal Clock See Circadian Rhythms.
Jet Lag Condition resulting when travel across time zones leaves a
person feeling "out of sync" with local time at his or her destination.
Melatonin A naturally occurring hormone associated with sleep. Synthetic
forms of melatonin are sold as over-the-counter sleep aids, although clinical data supporting melatonin
use are insufficient.
Microsleeps Fleeting, uncontrollable episodes of sleep occurring when
one is awake. Although they may last only a few seconds, microsleeps can cause car
accidents, machinery-related accidents, and other dangerous conditions.
Narcolepsy A sleep disorder marked by sudden, uncontrollable urges
to sleep, causing an individual to fall asleep at inappropriate times. Medications
and behavioral approaches such as scheduled naps can help control narcolepsy.
Nightmare A frightening dream that can cause an individual to wake
up. Nightmares typically occur during REM sleep.
Non-benzodiazepines A class of sleep medicines. Currently available
medicines in this group typically do not lead to daytime drowsiness.
NREM Sleep Non-rapid eye movement sleep. A stage of sleep in which
brain activity and bodily functions slow down. NREM sleep accounts for the largest
portion of the sleep cycle.
See REM Sleep.
Progressive Relaxation A technique that involves relaxing the body's
muscle groups in a progressive sequence, usually starting at the toes and moving
upward toward the head.
REM Sleep Rapid eye movement sleep. REM sleep occurs in brief spurts
of increased activity in the brain. REM is considered the dreaming stage
of sleep. It is characterized by the darting of the eyes under the eyelids.
Restless Legs Syndrome (RLS) A disorder that causes a strong urge to
move your legs. This urge to move often occurs with strange and unpleasant feelings
in your legs. Moving your legs relieves the urge and the unpleasant feelings.
Sleep Apnea A condition characterized by temporary breathing interruptions
during sleep. The pauses in breathing can occur dozens or even hundreds of times
a night. Symptoms include loud snoring
and a gasping or snorting sound when the
sleeping individual starts to breathe again. Although the individual may not be
aware of having sleep apnea, the condition can disrupt the quality of sleep and
result in daytime fatigue. The most common type, obstructive sleep apnea, occurs
when the tongue or other soft tissue blocks the airway. Treatments include breathing
devices that keep the airway open during sleep, and surgery that reduces the amount
of soft tissue near the airway.
Sleep Center A laboratory or other clinical facility equipped to diagnose
sleep disorders.
Sleep Cycle A sequence of sleep stages that usually begins with a period
of about 80 minutes of NREM sleep followed by about
10 minutes of REM sleep. This cycle of approximately
90 minutes is repeated four to six times each night. If the sequence is interrupted
(for example, by external noise or a sleep disorder), the quality of sleep can suffer.
Sleep Deprivation
A general lack of the necessary amount of sleep due to an externally imposed restriction of the opportunity to sleep.
Snoring Hoarse, often loud breathing sound that occurs during sleep.
Snoring often occurs when the soft palate in the mouth vibrates. Snoring may be
a sign of sleep apnea.
Teeth Grinding (Bruxism) Occurring during sleep, teeth grinding can
disrupt sleep and lead to daytime fatigue. It can also damage teeth, gums, and jaw
bones. To help prevent damage, dentists often recommend using a plastic mouth guard.