Sleep Apnea Types, Symptoms, Causes, and Treatment
Author: Disabled World (DW)
Updated/Revised Date: 3 Nov 2026
Table of Contents:
Synopsis - Definition - About This Section - FAQs - Publications - Subtopics
Synopsis
Learn about sleep apnea, including central, obstructive, and complex types, common symptoms and causes, diagnosis with a sleep study, and CPAP treatment options.
At a Glance
- 1 - A BiPAP machine gives a higher air pressure when breathing in and a lower one when breathing out.
- 2 - Sleep apnea is classified as a dyssomnia, and each pause in breathing can occur 5 to 30 or more times an hour.
- 3 - When breathing pauses, carbon dioxide builds up in the blood and signals the brain to wake the person to breathe.
- 4 - A loss of around 5 kg to 10 kg may be enough to dramatically reduce the severity of the disorder, since obesity is a common cause.
Topic Definition
- Sleep Apnea
Sleep apnea is a sleep disorder marked by repeated pauses in breathing, or by shallow and infrequent breathing, while a person sleeps. Each pause, known as an apnea, can last from a few seconds to several minutes and may happen dozens of times an hour, while a shallow breathing event is called a hypopnea. There are three forms: central sleep apnea, where the brain fails to signal the muscles to breathe; obstructive sleep apnea, where the airway becomes blocked; and complex sleep apnea, which combines features of both. Because these interruptions lower blood oxygen and raise carbon dioxide, the condition is usually diagnosed through an overnight sleep study called a polysomnogram, and it is commonly managed with a continuous positive airway pressure device that keeps the airway open during sleep.
Overview
Sleep apnea (sleep apnoea in British English) is a sleep disorder characterized by pauses in breathing or instances of shallow or infrequent breathing during sleep.
Each pause in breathing, called an apnea, can last for several seconds to several minutes, and may occur 5 to 30 times or more in an hour. Each abnormally shallow breathing event is called a hypopnea.
Sleep apnea is classified as a dyssomnia, meaning a disorder that affects the amount, quality, or timing of sleep. When breathing is paused, carbon dioxide builds up in the bloodstream. Chemoreceptors in the brain and in the large arteries sense the high carbon dioxide levels. The brain is signaled to wake the person sleeping and breathe in air. Breathing normally will restore oxygen levels and the person will fall asleep again. Sleep apnea is often diagnosed with an overnight sleep test called a polysomnogram, or sleep study.
There are three forms of Sleep Apnea: central, obstructive, and complex:
Central Sleep Apnea
In central sleep apnea, the basic neurological controls for breathing rate malfunctions and fails to give the signal to inhale, causing the individual to miss one or more cycles of breathing.
If the pause in breathing is long enough, the percentage of oxygen in the circulation will drop to a lower than normal level (hypoxia) and the concentration of carbon dioxide will build to a higher than normal level (hypercapnia).
In turn, these conditions of hypoxia and hypercapnia will trigger additional effects on the body.
Obstructive Sleep Apnea
Common symptoms include loud snoring, restless sleep, and sleepiness during the daytime. Diagnostic tests include home oximetry or polysomnography in a sleep clinic.
The early reports of obstructive sleep apnea in the medical literature described individuals who were very severely affected, often presenting with severe hypoxemia, hypercapnia and congestive heart failure.
Tracheostomy was the recommended treatment and, though it could be life-saving, post-operative complications in the stoma were frequent.
Some treatments involve lifestyle changes, such as avoiding alcohol or muscle relaxants, losing weight, and quitting smoking.
Complex Sleep Apnea
Complex sleep apnea, now usually called treatment-emergent central sleep apnea, is a form of sleep apnea first described in the 2000s.
Patients with complex sleep apnea exhibit OSA, but upon application of positive airway pressure, the patient exhibits persistent central sleep apnea. This central apnea is most commonly noted while on CPAP therapy, after the obstructive component has been eliminated. This has long been seen in sleep laboratories, and has historically been managed either by CPAP or Bi-Level therapy.
Adaptive servo-ventilation modes of therapy have been introduced to attempt to manage this complex sleep apnea. Studies have demonstrated marginally superior performance of the adaptive servo ventilators in treating Cheyne-Stokes breathing. However, the large SERVE-HF trial, published in 2015, found that adaptive servo-ventilation raised the risk of death in people with heart failure with reduced ejection fraction and central sleep apnea, so it is not used for those patients.
Diagnosis
The diagnosis of sleep apnea is based on the conjoint evaluation of clinical symptoms (e.g., excessive daytime sleepiness and fatigue) and of the results of a formal sleep study (polysomnography, or reduced channels home-based test).
The latter aims at establishing an "objective" diagnosis indicator linked to the quantity of apneic events per hour of sleep (Apnea Hypopnea Index(AHI), or Respiratory Disturbance Index (RDI)), associated to a formal threshold, above which a patient is considered as suffering from sleep apnea, and the severity of their sleep apnea can then be quantified.
- Mild OSA (Obstructive Sleep Apneas) ranges from 5 to 14.9 events per hour of sleep.
- Moderate OSA falls in the range of 15-29.9 events per hour of sleep.
- Severe OSA would be a patient having over 30 events per hour of sleep.
Treatment of Sleep Apnea
The most common treatment and arguably the most consistently effective treatment for sleep apnea is the use of a continuous positive airway pressure (CPAP) device, which splints the patient's airway open during sleep employing a flow of pressurized air into the throat.
A CPAP machine gives the same steady pressure when breathing in and out, whereas a BiPAP machine gives a higher pressure when breathing in and a lower pressure when breathing out, and is used for people who cannot tolerate CPAP or who need more support. Other treatments include custom oral appliances, an implanted hypoglossal nerve stimulator for some people with moderate to severe obstructive sleep apnea, and, since December 2024, the weight loss medicine tirzepatide (Zepbound) for adults with moderate to severe obstructive sleep apnea and obesity.
Severity
Severity of sleep apnea depends on how often the breathing is interrupted:
- Normal - less than five interruptions an hour
- Mild sleep apnea - between 5 and 15 interruptions an hour
- Moderate sleep apnea - between 15 and 30 interruptions an hour
- Severe sleep apnea - over 30 interruptions an hour.
Causes of Sleep Apnea
- Nasal congestion and obstruction.
- Large tonsils, especially in children.
- Medications, such as sleeping tablets and sedatives.
- Facial bone shape and the size of muscles, such as an undershot jaw.
- Certain illnesses, like reduced thyroid production or the presence of a large goiter (swelling of the thyroid gland in the neck)
- Alcohol, especially in the evening, relaxes the throat muscles and hampers the brain's reaction to sleep disordered breathing.
- Obesity is one of the most common causes of sleep apnea. A loss of around 5 kg to 10 kg (11 to 22 pounds) may be enough to dramatically reduce the severity of the disorder.
Statistics
- The Wisconsin Sleep Cohort Study estimated in 1993 that roughly one in every 15 Americans was affected by at least moderate sleep apnea. It also estimated that in middle-age as many as nine percent of women and 24 percent of men were impacted, undiagnosed and untreated.
- The costs of untreated sleep apnea reach further than just health issues. It is estimated that in the U.S. the average untreated sleep apnea patient's annual health care costs $1,336 more than an individual without sleep apnea. This may cause $3.4 billion/year in additional medical costs. A 2016 analysis for the American Academy of Sleep Medicine estimated that undiagnosed obstructive sleep apnea costs the U.S. about $149.6 billion a year.
Frequently Asked Questions
What is the difference between snoring and sleep apnea?
Snoring is the sound of vibrating throat tissue, while sleep apnea involves actual pauses in breathing, and loud snoring can be one of its symptoms.
How is sleep apnea diagnosed?
It is diagnosed by evaluating symptoms such as daytime sleepiness alongside a sleep study, either a full polysomnogram or a reduced channel home based test.
What does the Apnea Hypopnea Index measure?
The Apnea Hypopnea Index counts the number of apnea and hypopnea events per hour of sleep and is used to classify sleep apnea as mild, moderate, or severe.
Can children have sleep apnea?
Yes, children can have sleep apnea, and large tonsils are a common contributing cause in younger patients.
How does alcohol affect sleep apnea?
Alcohol relaxes the throat muscles and dulls the brain response to disordered breathing, which can worsen sleep apnea, especially when consumed in the evening.
Is sleep apnea linked to other health conditions?
Yes, reduced thyroid production, a large goiter, obesity, and facial bone shape can all contribute to sleep apnea, and untreated cases raise health care costs.
What is a polysomnogram?
A polysomnogram is an overnight sleep test in which sensors record measures such as blood oxygen level, breathing events, and REM sleep stage over time.
Are there alternatives to CPAP for sleep apnea?
Options include custom oral appliances that move the jaw forward, positional therapy, weight loss, surgery, and an implanted nerve stimulator for some people. A sleep specialist can help choose the right option.
Curated and edited by Ian C. Langtree, Founder and Editor-in-Chief, Disabled World. This section is maintained by the Disabled World editorial team. Last updated: