Sleep Studies

Sleep studies are noninvasive, overnight exams that allow doctors to monitor your brain and body while you sleep. 

It is usually conducted in a sleep lab that is set up for overnight stays in a hospital or sleep center. 

An EEG monitors your sleep stages and the cycles of REM and non-REM/NREM sleep that you experience during the night, to determine if there is any disruption in your sleep pattern. 

Other things that are measured during a sleep study are eye movements, oxygen levels in the blood (via a sensor – there is no needle involved), heart and breathing rates, snoring, and body movements.

In most cases, the sleep data you provide will be collected by a technologist, and then it will be analyzed by your physician. 

Your results may take up to two weeks to come back, at which point you’ll schedule a follow-up to discuss them.

Types Of Sleep Studies

A sleep study collects data about a person’s body while they are sleeping. 

Depending on a person’s symptoms and the sleep disorders they may have, there are different types of sleep studies available.


During polysomnography, a sleep technician monitors a patient who stays overnight at a specialized clinic. 

A number of functions are measured throughout the night, including eye movements, brain activity, respiratory effort, blood oxygen level, body position, and snoring.

Multiple Sleep Latency Test

The multiple sleep latency test measures how quickly a person falls asleep and enters REM sleep during daytime naps. 

The primary purpose of this test is to diagnose excessive daytime sleepiness that may be caused by narcolepsy or an unknown cause (idiopathic hypersomnia).

CPAP Titration

A common treatment for sleep apnea is continuous positive airway pressure (CPAP). 

CPAP titration is the process of determining the amount of air pressure a patient needs from their CPAP so that it can be properly programmed for them to use at home. 

CPAP titration usually involves a second sleep study.

Split-Night Study

A split-night sleep study may be recommended when sleep apnea is strongly suspected. 

Split-night studies involve polysomnography during the first half of the night, followed by a CPAP titration during the second half.

Home Sleep Apnea Testing

Sleep apnea tests at home monitor a patient’s breathing patterns, heart rate, and other factors while they sleep. 

Home testing is generally less accurate than polysomnography, however, and the process is not overseen by a technician.

What Can A Sleep Study Diagnose?

Many sleep disorders can be diagnosed with a sleep study, including:


Insomnia is described as a persistent difficulty starting, staying, and consolidating sleep. 

There are many causes and symptoms of insomnia, but its diagnosis rests on two essential components: sleep difficulties that persist even when adequate opportunities for normal sleep exist, and daytime impairment that is directly related to poor sleep.

Chronic insomnia is characterized by symptoms occurring at least three times per week for at least three months. 

It is known as short-term insomnia if it lasts less than three months. 

Patients with insomnia symptoms may, in rare cases, not meet the criteria for short-term insomnia and may require some form of treatment. 

Such cases are referred to as other insomnia.

Insomnia manifests in different ways, but most diagnoses fall into one of two categories:

Sleep-Onset Insomnia

An individual experiencing sleep-onset insomnia has difficulty falling asleep. 

Some people who suffer from this type of insomnia have a difficult time relaxing in bed, as well as people whose circadian rhythm is off due to jet lag or having irregular work schedules.

Sleep Maintenance Insomnia

As the name suggests, sleep maintenance insomnia is characterized by difficulty staying asleep after falling asleep. 

The condition is common among elderly individuals, as well as those who consume alcohol, caffeine, and tobacco before bed. 

Several disorders, like sleep apnea and periodic limb movement disorder, can also cause sleep maintenance insomnia.

There are people who suffer from mixed insomnia, which involves both sleep-onset and sleep maintenance difficulties, and people with chronic insomnia may notice that these symptoms shift over time.

Sleep Apnea

The condition of sleep apnea is characterized by abnormal breathing while sleeping. 

People with sleep apnea experience multiple pauses in their breathing when they sleep. 

Temporary breathing lapses reduce the quality of sleep and affect the body’s oxygen supply, resulting in potentially serious health effects.

In the United States, sleep apnea is one of the most common sleep disorders. 

Children and adults can be affected, as well as people of both sexes, although it is more common in men.

In light of sleep apnea’s prevalence and potential health consequences, it is important that people are informed about what sleep apnea is and understand its types, symptoms, causes, and treatments.

Sleep apnea can be categorized into three types:

Obstructive Sleep Apnea (OSA)

Typically, OSA results when the airway at the back of the throat becomes physically blocked. 

This results in temporary lapses in breathing.

Central Sleep Apnea (CSA)

CSA occurs when the brain’s system for controlling breathing muscles malfunctions, resulting in slower and shallower breathing.

Mixed Sleep Apnea

A person who has both OSA and CSA is said to have mixed sleep apnea or complex sleep apnea.

Symptoms and treatments of OSA and CSA differ because the underlying causes are distinct.

Restless Leg Syndrome

Restless legs syndrome (RLS), also called Willis Ekbom disease, causes uncomfortable sensations in the legs like itchiness, prickling, pulling, or crawling. 

There is an overwhelming urge to move the legs as a result of these sensations.

A person with RLS may walk, stretch, or shake their legs to relieve the symptoms. 

A person’s symptoms tend to worsen when they’re inactive, such as when they’re relaxing or lying down. 

RLS symptoms disrupt sleep as a result.

Approximately 5-10% of adults and 2 to 4% of children in the U.S. suffer from RLS, which more often affects women than men. 

RLS can affect people of any age, but older adults usually experience the most severe symptoms.


Narcolepsy affects the sleep-wake cycle. 

Its primary symptom is excessive daytime sleepiness (EDS), which is the result of an inability of the brain to properly regulate wakefulness and sleep.

Rapid eye movement (REM) sleep occurs in the final stage of normal sleep, usually an hour after falling asleep. 

In narcolepsy, REM sleep begins much earlier than usual, often within minutes of falling asleep.

People with narcolepsy experience REM quickly due to changes in the brain that disrupt sleep. 

These disruptions can also cause daytime sleepiness and other symptoms of narcolepsy.

Types Of Narcolepsy

Narcolepsy has two types: type 1 (NT1) and type 2 (NT2).

Narcolepsy Type 1

The NT1 gene is associated with cataplexy, a condition characterized by sudden loss of muscle tone. 

NT1 is also known as “narcolepsy with cataplexy.”

Patients with NT1 do not always experience episodes of cataplexy. 

A person with NT1 may also have low levels of hypocretin-1, a brain chemical that regulates wakefulness.

Many people with hypocretin-1 deficiency eventually experience cataplexy even if it is not present at the time of diagnosis.

Narcolepsy Type 2

In the past, NT2 was called “narcolepsy without cataplexy”. 

The symptoms of NT2 are similar to those of NT1, but the patients do not exhibit cataplexy or low levels of hypocretin-1.

Persons diagnosed with NT2 can be reclassified as NT1 if they develop cataplexy or low hypocretin-1 levels later in life. 

About 10% of people with NT2 are reclassified as NT1 later on.

Periodic Limb Movement Disorder

PLMD, or periodic limb movement disorder, is a sleep disorder that affects approximately 4% to 11% of the population. 

PLMD causes repetitive jerking, cramping, or twitching of the lower limbs during sleep. 

Periodic limb movements (PLMS) occur every 5 to 90 seconds for up to an hour. 

Even if they do not wake up, the movements disrupt their sleep, causing daytime sleepiness and fatigue.

As the movements occur during sleep, the affected individual may not realize they are suffering from a sleep disorder. 

They will experience symptoms such as waking up during the night without any apparent reason or feeling tired during the day. 

These symptoms may lead them to believe they suffer from insomnia. 

A sleep partner is more likely to notice the movements and mention them to the affected individual.

While it is quite rare among children, PLMD can develop at any age. 

Comorbid sleep apnea or neuropsychiatric disorders increase a child’s risk, as does having a parent with RLS. 

Over 45% of older adults appear to be suffering from PLMD, and the risk increases significantly with age. 

Both men and women are affected equally by PLMD.


Sleepwalking, or somnambulism, is a sleep disorder marked by walking or performing other complex behaviors while mostly asleep. 

Children are more likely to suffer from it than adults, and it is more likely to occur if a person has a family history of it, is sleep deprived, or has difficulty sleeping through the night.

A sleepwalking episode can cause injury, and drowsiness during the day is associated with sleepwalking. 

Many people may not need active treatment, but when episodes are more frequent or intense, several treatment options may be beneficial.

This type of sleeping disorder is known as a parasomnia. 

Parasomnias are abnormal sleep behaviors. 

The actions that occur during parasomnia episodes are abnormal because parasomnias fluctuate between sleep and wakefulness.

A parasomnia can be classified according to the part of the sleep cycle in which it occurs. 

Sleepwalking occurs during non-REM (NREM) sleep, usually in stage III of the sleep cycle, which is also known as deep sleep. 

Sleepwalking is classified as an NREM disorder of arousal, along with sleep talking, confusional arousals, and sleep terrors.

Sleep Talking

Sleep talking, also known as somniloquy, is a sleep disorder characterized by talking during sleep without being aware of it. 

Sometimes sleep talking involves complex monologues or dialogues, or it can be simple gibberish or mumbling. 

For most people, this is a rare and short-lived condition.

The majority of people will experience at least one episode of sleep talking during their lives, making it one of the most common abnormal behaviors during sleep. 

The consequences and symptoms of sleep talking have been clarified by research, but there is still much unknown regarding the causes and treatment of this disorder.

Sleep talking has been distinguished from other forms of vocalization that can occur when sleeping, such as catathrenia, a breathing disorder that causes audible groans, or REM sleep behavior disorder (RBD), in which a person physically acts out their dreams.

REM Sleep Behavior Disorder

An individual suffering from REM sleep behavior disorder experiences vivid dreams while experiencing sudden movements and vocalizations. 

It is a specific type of parasomnia, characterized by abnormal behaviors during sleep.

The body experiences temporary muscle paralysis, called atonia, during normal REM sleep, while the brain shows wakeful activity. 

A person’s blood pressure rises, their breathing becomes irregular, and their eyes dart in all directions rapidly (hence the term “rapid eye movement”). 

In REM sleep, the temporary paralysis allows us to lie still while our brains are active while dreaming. 

A majority of skeletal muscles are affected by this paralysis, but not muscles involved in breathing, digestion, and some muscles that move the eyes. 

About 25 percent of a person’s sleep is REM, with most of it occurring during the second half of the night.

Individuals with REM sleep behavior disorder do not experience normal muscle paralysis, enabling them to act out their dreams physically. 

REM sleep behavior disorder can range from small muscle twitches and quiet sleep talking to loud shouting, punching, kicking, and grabbing their bed partner. 

Dreams associated with REM sleep behavior disorder are often intense and frightening. 

A person may dream of being chased or attacked, and they may unknowingly act out the dream in real life.

Sleep Studies Frequently Asked Questions

Sleep studies usually take place in a sleep lab during your normal sleeping hours. 

Recording brain and body activity during sleep can be used to diagnose and treat sleep disorders.

95 percent is considered normal saturation. 

Desaturation of 86 percent or less is described as mild, 80 to 85 percent as moderate, and 79 percent or less as severe.

Surface electrodes will be placed on your face and your scalp during a sleep study and will record electrical signals that will be sent to the measuring equipment. 

Your brain and muscle activity generate these signals, which are recorded digitally. 

Breathing is measured by belts around your chest and abdomen.

Stress, irregular sleep schedules, poor sleeping habits, mental health disorders such as anxiety and depression, physical illnesses and pain, medications, neurological problems, and specific sleep disorders are common causes of insomnia.

There are three types of insomnia: transient insomnia (less than one week), acute insomnia (short-term), and chronic insomnia (long-term). 

Insomnia is the most common type of sleep disorder, involving difficulty falling asleep or staying asleep, or experiencing poor quality sleep despite having ample opportunity to do so.

Acute insomnia often goes away on its own, but it can still be dangerous. 

Chronic insomnia sufferers can take steps to lessen their symptoms.

Researchers do not know what causes REM sleep disorder. 

Studies on animals suggest that it has to do with certain neural pathways in the brain. 

Without RBD, certain neural pathways inhibit muscle activity during REM sleep, and disruption of these neural pathways results in REM sleep without atonia.

Medication is usually effective in managing this condition. 

The most frequently used medicine is clonazepam (Klonopin). 

In addition, your doctor may prescribe melatonin, a dietary supplement that can alleviate symptoms.

There are several options for treating REM sleep behavior disorder, including melatonin. 

You may be prescribed melatonin by your doctor, which may alleviate or reduce your symptoms. 

The effects of melatonin are comparable to those of clonazepam and are usually well tolerated.

REM sleep is characterized by rapid eye movements, even breathing, elevated blood pressure, and paralysis (loss of muscle tone). 

Nevertheless, the brain is highly active, and its electrical activity is similar to that during wakefulness. 

Dreams are usually associated with REM sleep.

Hypocretin (also known as orexin) is a brain chemical that regulates sleep, and it is thought that narcolepsy is caused by the lack of it. 

Hypocretin is thought to be deficient as a result of the immune system attacking parts of the brain.

Narcolepsy is characterized by five main symptoms, which are referred to as CHESS (Cataplexy, Hallucinations, Excessive Daytime Sleepiness, Sleep Paralysis, Sleep Disruption).

A polysomnogram and a Multiple Sleep Latency Test (MSLT) are usually necessary for the diagnosis of narcolepsy. 

Your physician can use a polysomnogram to measure brain activity during sleep, especially how frequently and when REM cycles occur.

Narcolepsy does not affect a person’s life expectancy, except in cases of accidents like falls.

PLMD is not known to have any specific cause. 

Some medications, however, have been shown to worsen the condition. 

Some of these medications are antidepressants, antihistamines, and antipsychotics.

 Low iron levels or problems with nerve conduction caused by diabetes or kidney disease can cause PLMD.

Primary PLMD is not considered medically serious, although complications may arise as a result of the condition. 

Primary PLMD is uncommon, according to the National Sleep Foundation.

In the absence of treatment, periodic limb movement disorder (PLMD) causes significant disability. 

Despite this, it is seldom diagnosed in clinical practice, perhaps due to a lack of awareness and/or inadequate diagnostic facilities.

Adults who have obesity and excess weight often suffer from obstructive sleep apnea due to the soft tissue in their mouths and throats. 

This soft tissue can block the airway during sleep when the throat and tongue muscles are relaxed.

In general, sleep apnea is a chronic disease that does not go away. 

After adolescence, anatomical structures tend to remain fixed. 

Thus, children with sleep apnea may retain hope that their condition will be successfully and definitively treated.