Sleep Disorders Glossary S

Sleep Disorders Glossary - S

Seasonal affective disorder [SAD]

SAD is the acronym for Seasonal affective disorder; form of depression occurring at certain seasons of the year, especially when the individual has less exposure to sunlight

The SCN generates a circadian rhythm of neuronal activity, which regulates many different body functions over a 24-hour period.

Sedative / Sleeping Pills

Sedative - also called a sleeping pill or hypnotic. It is a medication that has a calming effect and may be used to treat nervousness or restlessness. Sometimes used as a synonym for hypnotic.

Sedentary Situation

Sedentary situation is that, which does not require physical activity, such as working at a desk, watching television, sitting in a meeting or in a theater, etc.

Selective Serotonin Reuptake Inhibitors

Selective serotonin reuptake inhibitors are antidepressant drugs that act by blocking the reuptake of serotonin so that more serotonin is available to act on receptors in the brain. Examples include: Zoloft, Prozac, and Paxil.


Septoplasty is a surgical procedure to correct the shape of the septum of the nose. The goal of this procedure is to correct defects or deformities of the septum.


Septum is the thin partition or membrane that divides two cavities or soft masses of tissue in an organism.


Serotonin An organic compound, C 10H 12N 2O, formed from tryptophan and found in animal and human tissue, especially the brain, blood serum, and gastric mucous membranes, and active as a neurotransmitter and in vasoconstriction, stimulation of the smooth muscles, and regulation of cyclic body processes.

In animal studies, the inhibition of the formation of serotonin led to severe insomnia.


Shift-work is working during times other than the normal daytime hours of 9:00 a.m. to 5:00 p.m.


Siesta - rest or nap after the midday meal . This allows people in tropical climates to avoid the hottest part of the day; it also takes advantage of the body's normal post-lunch (postprandial) dip in alertness.

Short-term insomnia

Short-term insomnia is the temporary sleeplessness that occurs due to the ongoing stress, a temporary illness, or a traumatic experience.


A natural periodic state of rest for the mind and body, in which the eyes usually close and consciousness is completely or partially lost, so that there is a decrease in bodily movement and responsiveness to external stimuli.

During sleep the brain in humans and other mammals undergoes a characteristic cycle of brain-wave activity that includes intervals of dreaming.

Sleep Apnea

Sleep apnea is a serious sleep disorder that occurs when a persons breathing is interrupted during sleep. People with untreated sleep apnea stop breathing repeatedly during their sleep, sometimes hundreds of times during the night.

Sleep apnea is a true breathing obstruction, which requires the sleeper to awaken to begin breathing again. A person with sleep apnea wakes up many times a night to regain breathing, but usually remembers nothing at all about the awakenings.

Sleep Architecture

Sleep architecture is the structure of the sleep cycle and wakefulness as it occurs over a period of sleep. NREM/REM stage and cycles of sleep and time spent in each stage. It is Also called sleep timing mechanism. It is o ften displayed in the form of a histogram.

Sleep Center

Sleep center is a localized area in the brain believed to control sleep.

Sleep Cycle

Sleep cycle is the cycle in which non-REM and REM sleep alternate in 90- to 110- minute phases. A normal sleep pattern has 4 to 5 sleep cycles. Sleep cycle is term used by scientists and sleep researchers to describe the pattern of sleep stages, especially the NREM-REM cycle.

Sleep Debts

Sleep debt is the cumulative effect of not getting enough sleep. The body seems to maintain an awareness of the cumulative amount of a person's missed sleep, when that person does not get enough sleep. Unlike sleep debt, a sleep surplus cannot be accumulated .

Sleep Deprivation

Sleep is defined as lack of adequate sleep. Sleep deprivation develops as a result of periods of less sleep than you normally get. The average person gets 8 hours of sleep for every 16 hours they are awake.

Thus, individuals exist in a daily equilibrium in which a relatively small amount of sleep loss causes increased sleepiness i.e. sleep deprivation.

Sleep Disorders

Sleep disorders are the disorders in sleep pattern. Sleep is a complex neurological state. Its primary function is rest and restoring the body's energy levels.

Repeated interruption of sleep by breathing abnormalities such as cessation of breathing (apnea) or heavy snoring, leads to fragmented sleep and abnormal oxygen and carbon dioxide levels in the blood.

Sleep Efficiency / Sleep Efficiency Index

Sleep efficiency is the proportion of sleep in the period potentially filled by sleep; that is, the ratio of total sleep time in bed.

Sleep Episode

Sleep Episode is the total time interval of sleep that may be voluntary or involuntary.

Sleep Extension

Sleep Extension - Extending sleep time by increasing the bedtime.

Sleep Fragmentation

Sleep Fragmentation - Brief arousals that occur throughout the night, that reduce the total amount of time spent in the deeper levels of sleep. Frequent episodes of sleep fragmentation lead to sleep deprivation. sleep interruption due to frequent or sustained awakenings or early morning awakenings.

Sleep Hygiene

Sleep hygiene is the practice of following simple guidelines to ensure restful, effective sleep promoting daytime alertness and helping avoid the onset of sleep disorders. Trouble sleeping and daytime sleepiness can be indications of poor sleep hygiene .

Sleep Hyperhidrosis / Night Sweats

Night sweats, scientifically known as Sleep hyperhidrosis, is defined as, the occurrence of excessive sweating during sleep i.e., Sweating at night even when it isn't excessively hot in your bedroom and day sweats were defined as, excessive sweating during the daytime.

Sleep Inertia

Sleep inertia is a physiological state characterised by a decline in motor dexterity and a subjective feeling of grogginess, immediately following an abrupt awakening from deep sleep. Typically, sleep inertia lasts between 1 and 30 minutes.

Sleepiness / Somnolence / Drowsiness

Sleepiness somnolence, drowsiness is quality or state of being sleepy. It is state where the subject finds it difficult to maintain the wakeful state and falls asleep if not actively kept aroused. Differs from simply a feeling of physical tiredness or listlessness.

Sleep Interruption

Sleep interruption is the breaks in the sleep architecture resulting in arousal and wakefulness.

Sleep Latency

Sleep latency the length of time that it takes to go from full wakefulness to falling asleep. During daytime, a sleep latency of 15-25 minutes is considered normal. A shorter sleep-latency is likely a sign that the person suffers from sleep-deprivation. A sleep-latency of less than five minutes would indicate either very unhealthy daytime sleepiness or some sort of sleep-disorder.

Sleep Log (Diary)

Sleep Log (Diary) is the daily, written record of a person's sleep-wake pattern containing such information as time of retiring and arising, bedtime, estimated total sleep time, number and duration of sleep interruptions, quality of sleep, daytime naps, medications usage or caffeine beverages, and nature of waking activities.

Sleep Maintenance Insomnia

Sleep maintenance insomnia is the inability to stay asleep or to resume sleep after waking in the middle of the sleep cycle.

Sleep Medicine

Sleep medicine is the science of the study of sleep and its processes. It also refers to the clinical practice of assessing and treating sleep disorders.

Sleep Mentation

Sleep mentation - the imagery and thinking (and emotion) experienced during sleep.

It is the thoughts, feelings, images, perceptions, hallucinations, and active dreams that take place during sleep.

Sleep Onset

Sleep onset is the transition from the awake to the sleep state, normally into NREM stage 1. It is t he time from when a person attempts to fall asleep until the onset of sleep. This sleep onset normally leads to NREM stage 1 sleep, but in certain conditions, such as infancy and narcolepsy, may lead to REM stage sleep.

Sleep Onset Imagery

Sleep Onset Imagery is a kaleidoscope of images and experiences during the moments following the sleep onset.

Sleep Onset Insomnia

Sleep onset insomnia is the insomnia characterized by a delay in falling asleep, lasting 30 minutes or longer, at the time when one goes to bed. The common cause of sleep onset insomnia is anxiety.

Sleep Onset REM Period (SOREMP)

Sleep Onset REM Period (SOREMP) is a typical beginning of sleep by entrance directly into stage REM . It is the REM periods within 15 minutes of sleep onset, considered to confirm the diagnosis of narcolepsy. As a result, narcoleptics often experience Hypnagogic Hallucinations as they are falling asleep.

Sleep Paralysis

Sleep paralysis is a condition characterized by paralysis of the body shortly after waking up (known as hypnopompic paralysis) or, less often, shortly before falling asleep (known as hypnagogic paralysis).

Sleep Period

Sleep Period is the time taken to complete one cycle of sleep activity.

Sleep Related Accidents

Sleep Related Accidents are the accidents caused by individuals who were sleep deprived and had impaired judgment.

Sleep Restriction

Sleep Restriction is a limitation of the number of sleep hours.

Sleep Restriction Therapy / Sleep Deprivation Therapy

Sleep restriction therapy is a behavioral treatment developed by Dr. Arthur Spielman and colleagues that follows a simple principle: Restricting the bedtime to only the number of hours asleep, then increase bedtime as sleep effectiveness increases.

Sleeping Sickness / African Sleeping Sickness

An often fatal, endemic infectious disease of humans and animals in tropical Africa, caused by either of two trypanosomes (Trypanosoma rhodesiense or T. gambiense) transmitted by the tsetse fly and characterized by fever, severe headache, and lymph node swelling in the early stages, followed by extreme weakness, sleepiness, and deep coma. Also called African sleeping sickness.

Sleep Spindles

Sleep spindles are one of several measures employed by the brain to keep a sleeper in an unconscious state. A Sleep spindle is burst of brain activity visible on an EEG that occurs during stage 2 sleep. It consists of 12-16 Hz waves that occur for 0.5 to 1.5 seconds.

Sleep Stage Demarcation

Sleep Stage Demarcation - The significant polysomnographic characteristics that distinguish the boundaries of the sleep stages. It is the distinctive stages of sleep as demonstrated by EEG patterns. See Stages 1-4; REM Sleep.

Sleep Stage 1 / NREM Stage 1

During the first stage of sleep, we're half awake and half asleep. We drift in and out of sleep for about 5 to 10 minutes and can be awakened easily. Our eyes move very slowly and muscle activity slows. People awakened from stage 1 sleep often remember fragmented visual images.

Sleep Stage 2 / NREM Stage 2

Our eye movement stops and our brain waves (fluctuations of electrical activity that can be measured by electrodes) become slower, with occasional bursts of rapid waves called sleep spindles. The breathing pattern and heart rate start to slow down.

Sleep Stage 3 / NREM Stage 3

Stage 3, with delta waves, also called delta rhythms (1

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