In patients who are at high likelihood of having OSA, a randomized controlled trial found that home oximetry (a non-invasive method of monitoring blood oxygenation) may be adequate and easier to obtain than formal polysomnography. High probability patients were identified by an Epworth Sleepiness Scale (ESS) score of 10 or greater and a Sleep Apnea Clinical Score (SACS) of 15 or greater. Home oximetry, however, does not measure apneic events or respiratory event-related arousals and thus does not produce an AHI value.

When infants have a lower birth weight or younger gestational age, there is a greater risk of infantile apnea. With the advancement of neonatal intensive care units and the greater technology available, there are more successful premature births compared to the past. With the greater number of premature infants being born, there is also a greater number of children with infantile apnea. Approximately 85 percent of infants born with a weight less than experience infantile apnea within the first month after birth. This risk decreases to 25 percent for infants weighing less than . Studies have found that almost 2% of the pediatric population experience obstructive sleep apnea.

Oximetry, which may be performed over one or several nights in a person's home, is a simpler, but less reliable alternative to a polysomnography. The test is only recommended when requested by a physician and should not be used to test those without symptoms. Home oximetry may be effective in guiding prescription for automatically self-adjusting continuous positive airway pressure.

In-hospital monitors in the NICU typically measure respiratory movements, heartrate, and pulse oximetry. Central apnea can be detected quickly since it results in absence of respiratory movements. Obstructive apnea can be detected when the level of oxygen has declined in the blood and/or results in slowing of the heart rate.

Home apnea monitors (which must be distinguished from infant monitors that are designed only to allow parents to listen to the infant remotely) most frequently measure only respiratory movements and/or heart rate. They are generally used with premature infants who are otherwise ready for discharge, but who continue to require supplemental oxygen or medication for mild residual AOP. Home apnea monitoring is typically required for 6–12 weeks after discharge.

Since AOP is fundamentally a problem of the immaturity of the physiological systems of the premature infant, it is a self-limited condition that will resolve when these systems mature. It is unusual for an infant to continue to have significant problems with AOP beyond 42 weeks post-conceptual age.

Infants who have had AOP are at increased risk of recurrence of apnea in response to exposure to anesthetic agents, at least until around 52 weeks post-conceptual age.

There is no evidence that a history of AOP places an infant at increased risk for SIDS. However, any premature infant (regardless of whether they have had AOP) is at increased risk of SIDS. It is important that other factors related to SIDS risk be avoided (exposure to smoking, prone sleeping, excess bedding materials, etc.)

Polysomnography in diagnosing OSA characterizes the pauses in breathing. As in central apnea, pauses are followed by a relative decrease in blood oxygen and an increase in the blood carbon dioxide. Whereas in central sleep apnea the body's motions of breathing stop, in OSA the chest not only continues to make the movements of inhalation, but the movements typically become even more pronounced. Monitors for airflow at the nose and mouth demonstrate that efforts to breathe are not only present but that they are often exaggerated. The chest muscles and diaphragm contract and the entire body may thrash and struggle.

An "event" can be either an apnea, characterised by complete cessation of airflow for at least 10 seconds, or a hypopnea in which airflow decreases by 50 percent for 10 seconds or decreases by 30 percent if there is an associated decrease in the oxygen saturation or an arousal from sleep. To grade the severity of sleep apnea, the number of events per hour is reported as the apnea-hypopnea index (AHI). An AHI of less than 5 is considered normal. An AHI of 5-15 is mild; 15-30 is moderate and more than 30 events per hour characterizes severe sleep apnea.

After a patient receives a diagnosis, the diagnosing physician can provide different options for treatment.

- Mechanical regulation of airflow and/or airway pressure:

- An experimental pacemaker for the diaphragm has shown promising results in overcoming central sleep apnea.

Mixed apnea is a combination of both central and obstructive factors. The majority of premature infants with sleep apnea have mixed apnea.

Excess body weight is thought to be an important cause of sleep apnea. In weight loss studies of obese and overweight individuals, those who lose weight show reduced apnea frequencies and improved Apnoea–Hypopnoea Index (AHI) compared to controls.

Polysomnograms can be used to help diagnose UARS. Patient who have UARS typically show multiple EEG arousals during the sleep study and little to no polygraphic evidence of obstructive sleep apnea or decreased levels of oxygen. UARS arousals, or respiratory-effort related arousals, typically last for one to three breaths. These arousals may be due to snoring, but patients do not need to snore in order to have UARS. Polysomnogram patterns must exhibit no evidence of apneas or hypopneas in order to be lead to a diagnosis of UARS. Even with polysomnography, diagnosis of UARS may be difficult because of insufficient means of measuring changes in airflow. This lack of sensitivity in detection may lead to misdiagnosis, as minor undetectable changes in airflow may still be responsible for the arousals. In order to definitively diagnose UARS, there must be a demonstrated pattern of greater negative esophageal pressures which are then followed by a rapid change to a more positive level with a sleep arousal. This can be confirmed with invasive polysomnography that uses an esophageal balloon transducer and full pneumotachograph.

Based on symptoms, patients are commonly misdiagnosed with chronic fatigue syndrome, fibromyalgia, or a psychiatric disorder such as ADHD or depression.

People with neuromuscular disorders or hypoventilation syndromes involving failed respiratory drive experience central hypoventilation. The most common treatment for this form is the use of non-invasive ventilation such as a BPAP machine.

A diagnosis of sleep apnea requires determination by a physician. The examination may require a study of an individual in a sleep lab, although the AAST has said a two belt IHT (In Home Test) will replace a PSG for diagnosing obstructive apnea. There, the patient will be monitored while at rest, and the periods when breathing ceases will be measured with respect to length and frequency. During a PSG (polysomnography) (a sleep study), a person with sleep apnea shows breathing interruptions followed by drops/reductions in blood oxygen and increases in blood carbon dioxide level.

- In adults, a pause must last 10 seconds to be scored as an apnea. However, in young children, who normally breathe at a much faster rate than adults, shorter pauses may still be considered apneas.

- Hypopneas in adults are defined as a 30% reduction in air flow for more than ten seconds, followed by oxygen-saturation declines of at least 3% or 4% per the AASM stndards. and/or EEG arousal. The Apnea-Hypopnea Index (AHI) is expressed as the number of apneas or hypopneas per hour of sleep.

As noted above, in central sleep apnea, the cessation of airflow is associated with the absence of physical attempts to breathe; specifically, polysomnograms reveal correlation between absence of rib cage and abdominal movements and cessation of airflow at the nose and lips. By contrast, in obstructive sleep apnea, pauses are not correlated with the absence of attempts to breathe and may even be correlated with more effortful breathing in an instinctive attempt to overcome the pressure on the sufferer's airway. If the majority of a sleep-apnea sufferer's apneas/hypopneas are central, his condition is classified as central; likewise, if the majority are obstructive, his condition is classified as obstructive.

One treatment for obstructive hypopnea is continuous positive airway pressure (CPAP). CPAP is a treatment in which the patient wears a mask over the nose and/or mouth. An air blower forces air through the upper airway. The air pressure is adjusted so that it is just enough to maintain the oxygen saturation levels in the blood. Another treatment is sometimes a custom fitted oral appliance. The American Academy of Sleep Medicine's protocol for obstructive sleep apnea (OSA) recommends oral appliances for those who prefer them to CPAP and have mild to moderate sleep apnea or those that do not respond to/cannot wear a CPAP. Severe cases of OSA may be treated with an oral appliance if the patient has had a trial run with a CPAP. Oral Appliances should be custom made by a dentist with training in dental sleep medicine. Mild obstructive hypopnea can often be treated by losing weight or by avoiding sleeping on one's back. Also quitting smoking, and avoiding alcohol, sedatives and hypnotics (soporifics) before sleep can be quite effective. Surgery is generally a last resort in hypopnea treatment, but is a site-specific option for the upper airway. Depending on the cause of obstruction, surgery may focus on the soft palate, the uvula, tonsils, adenoids or the tongue. There are also more complex surgeries that are performed with the adjustment of other bone structures - the mouth, nose and facial bones.

Formal criteria for diagnosis of OHS are:

- Body mass index over 30 kg/m (a measure of obesity, obtained by taking one's weight in kilograms and dividing it by one's height in meters squared)

- Arterial carbon dioxide level over 45 mmHg or 6.0 kPa as determined by arterial blood gas measurement

- No alternative explanation for hypoventilation, such as use of narcotics, severe obstructive or interstitial lung disease, severe chest wall disorders such as kyphoscoliosis, severe hypothyroidism (underactive thyroid), neuromuscular disease or congenital central hypoventilation syndrome

If OHS is suspected, various tests are required for its confirmation. The most important initial test is the demonstration of elevated carbon dioxide in the blood. This requires an arterial blood gas determination, which involves taking a blood sample from an artery, usually the radial artery. Given that it would be complicated to perform this test on every patient with sleep-related breathing problems, some suggest that measuring bicarbonate levels in normal (venous) blood would be a reasonable screening test. If this is elevated (27 mmol/l or higher), blood gasses should be measured.

To distinguish various subtypes, polysomnography is required. This usually requires brief admission to a hospital with a specialized sleep medicine department where a number of different measurements are conducted while the subject is asleep; this includes electroencephalography (electronic registration of electrical activity in the brain), electrocardiography (same for electrical activity in the heart), pulse oximetry (measurement of oxygen levels) and often other modalities. Blood tests are also recommended for the identification of hypothyroidism and polycythemia.

To distinguish between OHS and various other lung diseases that can cause similar symptoms, medical imaging of the lungs (such as a chest X-ray or CT/CAT scan), spirometry, electrocardiography and echocardiography may be performed. Echo- and electrocardiography may also show strain on the right side of the heart caused by OHS, and spirometry may show a restrictive pattern related to obesity.

Among the natural remedies are exercises to increase the muscle tone of the upper airway, and one medical practitioner noting anecdotally that professional singers seldom snore, but there have been no medical studies to fully link the two.

People generally require tracheostomy and lifetime mechanical ventilation on a ventilator in order to survive. However, it has now been shown that biphasic cuirass ventilation can effectively be used without the need for a tracheotomy. Other potential treatments for Ondine's curse include oxygen therapy and medicine for stimulating the respiratory system. Currently, problems arise with the extended use of ventilators, including fatal infections and pneumonia.

Most people with CCHS (unless they have the Late Onset form) do not survive infancy, unless they receive ventilatory assistance during sleep. An alternative to a mechanical ventilator is diaphragm pacing.

Children with CCHS develop life-threatening episodes of apnea with cyanosis, usually in the first months of life. Medical evaluation excludes lesions of the brain, heart, and lungs but demonstrates impaired responses to build-up of carbon dioxide (hypercapnia) and decreases of oxygen in the circulation (hypoxia), the two strongest stimuli to increase breathing rate.

Polysomnography shows that hypoventilation is most marked during slow-wave sleep. In the most severe cases, hypoventilation is present during other nonrapid eye movement sleep stages and even wakefulness. A subset of CCHS patients are at very high risk for developing malignant neural crest-derived tumors, such as neuroblastoma.

The sequence of "PHOX2B" reveals mutations in 91% of the cases.

As in many disorders that are very rare, an infant with this unusual form of sleep apnea suffers from the probability that their physician has most likely never seen another case and will not recognize the diagnosis. In some locations, such as France, optimal management of patients, once identified, has been aided by the creation of a national registry and the formation of a network of centers.

Statistics on snoring are often contradictory, but at least 30% of adults and perhaps as many as 50% of people in some demographics snore. One survey of 5,713 American residents identified habitual snoring in 24% of men and 13.8% of women, rising to 60% of men and 40% of women aged 60 to 65 years; this suggests an increased susceptibility to snoring with age.

The primary treatment for children is the removal of enlarged tonsils and adenoids via a tonsillectomy and adenoidectomy. Orthodontic treatment is frequently recommended and CPAP may also be necessary for children with UARS.

Obesity hypoventilation syndrome is associated with a reduced quality of life, and people with the condition incur increased healthcare costs, largely due to hospital admissions including observation and treatment on intensive care units. OHS often occurs together with several other disabling medical conditions, such as asthma (in 18–24%) and type 2 diabetes (in 30–32%). Its main complication of heart failure affects 21–32% of patients.

Those with abnormalities severe enough to warrant treatment have an increased risk of death reported to be 23% over 18 months and 46% over 50 months. This risk is reduced to less than 10% in those receiving treatment with PAP. Treatment also reduces the need for hospital admissions and reduces healthcare costs.

Sleeping in a more upright position seems to lessen catathrenia (as well as sleep apnea). Performing regular aerobic exercise, where steady breathing is necessary (running, cycling etc.) may lessen catathrenia. Strength exercise, on the other hand, may worsen catathrenia because of the tendency to hold one's breath while exercising. Yoga and/or meditation focused on steady and regular breathing may lessen catathrenia.

EDS can be a symptom of a number of factors and disorders. Specialists in sleep medicine are trained to diagnose them. Some are:

- Insufficient quality or quantity of night time sleep.

- Misalignments of the body's circadian pacemaker with the environment (e.g. jet lag, shift work or other circadian rhythm sleep disorders).

- Another underlying sleep disorder, such as narcolepsy, sleep apnea, idiopathic hypersomnia or restless legs syndrome.

- Disorders such as clinical depression or atypical depression.

- Tumors, head trauma, anemia, kidney failure, hypothyroidism or an injury to the central nervous system.

- Drug abuse.

- Genetic predisposition

- Vitamin deficiency, such as Biotin deficiency

- Particular classes of prescription and OTC medication

An adult who is compelled to nap repeatedly during the day may have excessive daytime sleepiness; however, it is important to distinguish between occasional daytime sleepiness and excessive daytime sleepiness, which is chronic.

A number of tools for screening for EDS have been developed. One is the Epworth Sleepiness Scale which grades the results of a questionnaire. The ESS generates a numerical score from zero (0) to 24 where a score of ten [10] or higher may indicate that the person should consult a specialist in sleep medicine for further evaluation.

Another tool is the Multiple Sleep Latency Test (MSLT), which has been used since the 1970s. It is used to measure the time it takes from the start of a daytime nap period to the first signs of sleep, called sleep latency. The test is based on the idea that the sleepier people are, the faster they will fall asleep.

The Maintenance of Wakefulness Test (MWT) is also used to quantitatively assess daytime sleepiness. This test is performed in a sleep diagnostic center. The test is similar to the MSLT. However, during this test the patient is instructed to try to stay awake.

The hypercapnic state is routinely used to calibrate blood-oxygen-level dependent functional magnetic resonance imaging (BOLD fMRI), a modality that is sensitive to changes in blood oxygenation. However, this calibration crucially relies on the assumption that hypercapnia has no effect on neuronal function, which is a matter of debate.

Catathrenia is a rapid eye movement sleep parasomnia consisting of end-inspiratory apnea (breath holding) and expiratory groaning during sleep. Catathrenia is distinct from both somniloquy and obstructive sleep apnea. The sound is produced during exhalation as opposed to snoring which occurs during inhalation. It is usually not noticed by the person producing the sound but can be extremely disturbing to sleep partners. Bed partners generally report hearing the person take a deep breath, hold it, then slowly exhale; often with a high-pitched squeak or groaning sound.

Catathrenia typically, sometimes even exclusively, occurs during REM sleep, although it may also occur to a lesser degree during NREM sleep. Catathrenia begins with a deep inspiration. The sufferer holds her or his breath against a closed glottis, similar to the Valsalva maneuver. After a period of time and some blood oxygen desaturation, there is an arousal, followed by expiration. Expiration can be slow and accompanied by sound caused by vibration of the vocal cords or a simple rapid exhalation with no sound.

There is debate about whether the cause is physical or neurological, a question that requires further study. While some speculate about a direct correlation to high anxiety and stress or the concept that catathrenia is purely psychological, there is only anecdotal evidence of either proposed cause.

Catathrenia has been defined as a parasomnia in the International Classification of Sleep Disorders Diagnostic and Coding Manual (ICSD-2), but there is debate about its classification.

There are a few other similaritiesamongst catathrenia sufferers that have not yet been studied properly:

- Many catathrenia sufferers mention that they also suffer from some form of stress or anxiety in their lives.

- Sufferers themselves do not feel like they are experiencing a sleep apnea; the breath-holding appears to be controlled though the unconscious. Oxygen desaturation during a catathrenia episode is usually negligible.

- Many took part in sports activities during teens and twenties some which required breath-holding which included many types of sports such as swimming and even weight lifting. They find a certain level of comfort in breath-holding, and often do it while awake.

- Observations have been made of instances of breath holding during daily activities that require concentration.

- Some sufferers recalled suffering from lucid or stress dreams during their catathrenia episodes during their sleep.

- Some sufferers complain of having a painful chest upon waking from sleep.

Because catathrenia itself is not considered life-threatening, there has been very little research done in the medical community, and many experts assume that the way to treat catathrenia is to treat the underlying sleep apnea, though there is no conclusive evidence published that catathrenia results from sleep apnea, and sleep studies show that not all sufferers of catathrenia have been diagnosed with sleep apnea.

While doctors tend to dismiss it as an inconvenience, sufferers routinely describe the condition's highly negative effects on their daily lives including tiredness, low energy, dizziness and vertigo, work problems, relationship and social issues, and other physical and mental problems that could be associated with low sleep quality.