Written and medically reviewed by Kwaku Osafo-Mensah, MD
Pulmonary Medicine | Sleep Medicine | Diplomate, American Board of Sleep Medicine (ABSM)
Medically reviewed: August 2026
Obstructive sleep apnea and central sleep apnea can both cause repeated pauses or reductions in breathing during sleep.
But they occur for fundamentally different reasons.
In obstructive sleep apnea (OSA), the upper airway becomes narrowed or blocked while respiratory effort continues.
In central sleep apnea (CSA), breathing temporarily decreases or stops because respiratory effort itself becomes absent or markedly reduced during the event.
That distinction matters because the causes, sleep-study findings, and treatment approaches can be entirely unique.
The important question is not simply whether breathing stopped—it is why breathing stopped.
Quick Answer: Central vs. Obstructive Sleep Apnea
The simplest distinction is
Obstructive sleep apnea:
The airway is obstructed, but the person continues trying to breathe.
Central sleep apnea:
Airflow stops or substantially decreases because respiratory effort temporarily stops or markedly decreases.
A sleep study distinguishes these patterns by examining airflow together with respiratory effort.
Some patients can experience both obstructive and central events.
What Is Obstructive Sleep Apnea?
Obstructive sleep apnea occurs when the upper airway repeatedly narrows or collapses during sleep.
The brain continues sending signals to breathe, and the respiratory muscles continue working, but airflow is reduced or absent because the airway is obstructed.
During an obstructive apnea, the sleep study typically shows:
- Markedly reduced or absent airflow
- Continued respiratory effort
- Possible oxygen desaturation
- Often an arousal when the airway reopens
Obstructive sleep apnea is the most common type of sleep apnea. For a broader overview of obstructive sleep apnea—including symptoms, risk factors, diagnosis, testing, and treatment options—see Sleep Apnea: Symptoms, Testing, Treatment & What You Need to Know.
Risk can be influenced by upper-airway anatomy, body weight, age, craniofacial structure, nasal obstruction, alcohol, sedating medications, and other factors.
What Is Central Sleep Apnea?
Central sleep apnea is characterized by recurrent respiratory events in which airflow decreases or stops because respiratory effort is absent or markedly reduced during the event.
The upper airway is not necessarily mechanically blocked in the same way as during an obstructive apnea.
Instead, the problem involves instability or alteration of respiratory control.
A central apnea on a sleep study generally shows the following:
- Absent airflow
- Absent respiratory effort during the event
- Possible oxygen desaturation
- Possible arousal or subsequent ventilatory response
Central sleep apnea is not a single disease with one cause.
Different clinical conditions can produce central respiratory events through different mechanisms.
The Key Difference: Respiratory Effort
The most important physiologic distinction between obstructive and central apnea is respiratory effort.
Consider the following:
| Feature | Obstructive Apnea | Central Apnea |
|---|---|---|
| Airflow | Absent or markedly reduced | Absent or markedly reduced |
| Respiratory effort | Continues | Absent during the central portion |
| Upper-airway obstruction | Characteristic mechanism | Not the primary mechanism |
| Respiratory-control instability | May contribute to OSA physiology | Often important in CSA |
| Treatment | Directed primarily at maintaining airway patency and contributing factors | Depends strongly on cause and physiology |
This is why airflow alone cannot reliably distinguish every apnea type.
The effort channels matter.
How Does a Sleep Study Measure Respiratory Effort?
During laboratory polysomnography, respiratory effort is commonly assessed using belts positioned around the chest and abdomen.
These signals help determine whether the person continues attempting to breathe during a respiratory event.
In simplified terms:
Airflow absent + effort continues → obstructive pattern
Airflow absent + effort absent → central pattern
Actual sleep-study scoring follows standardized criteria and requires interpretation of the complete respiratory signals rather than relying on a simplified formula alone.
What Is a Mixed Apnea?
A mixed apnea contains both central and obstructive characteristics within the same respiratory event.
Typically, the event begins with absent respiratory effort and later develops respiratory effort while airflow remains absent.
In other words, the event has the following:
a central component followed by an obstructive component.
Mixed apneas illustrate why sleep-disordered breathing cannot always be divided into perfectly separate categories.
A person may demonstrate obstructive, central, and mixed events during the same study.
Does Having One Central Apnea Mean You Have Central Sleep Apnea?
No.
An occasional central apnea does not automatically establish a diagnosis of central sleep apnea syndrome.
Central events can occur in certain circumstances even in people who do not have a clinically significant central sleep apnea disorder.
Interpretation requires considering the following:
- Number of central events
- Central apnea index
- Proportion of respiratory events that are central
- Sleep stage
- Sleep-wake transitions
- Altitude
- Medications
- Medical conditions
- Overall breathing pattern
- Study quality
The presence of a central event and the diagnosis of a central sleep apnea disorder are not the same thing.
What Is the Central Apnea Index?
The Central Apnea Index (CAI) describes the average number of scored central apneas occurring per hour of sleep.
Like AHI, it is a frequency measurement.
A higher CAI indicates that central events occurred more frequently during the measured sleep period.
However, CAI should not be interpreted in isolation.
The diagnosis of a particular central sleep apnea disorder depends on the complete pattern and appropriate diagnostic criteria, not simply on one number.
AHI and CAI Are Not the Same Thing
AHI includes scored apneas and hypopneas meeting the applicable criteria.
The apnea component may include different event types.
CAI specifically describes central apneas.
For example, two people could have the same overall AHI while one has predominantly obstructive events and the other has a substantial central component.
The treatment implications could be completely unique.
For a broader explanation of respiratory indices, see AHI vs RDI vs REI: What’s the Difference on a Sleep Study?
What Causes Central Sleep Apnea?
Central sleep apnea can occur in association with several different physiologic and clinical situations.
Examples include:
- Heart failure and certain cardiovascular conditions
- Opioid or other respiratory-depressant medication exposure
- High altitude
- Neurologic disease or injury affecting respiratory control
- Certain medical disorders
- Treatment-emergent central sleep apnea
- Primary or idiopathic central sleep apnea in selected cases
The mechanism is not identical in all of these situations.
This variability is one reason treatment must be directed toward the specific type and cause of central sleep apnea, rather than treating every central event the same way.
Central Sleep Apnea and Heart Failure
Central sleep apnea can occur in patients with heart failure.
One breathing pattern associated with heart failure is Cheyne-Stokes respiration, which is characterized by a cyclical waxing and waning pattern of ventilation associated with central apneas or hypopneas.
This pattern reflects instability in respiratory control and circulation rather than simple upper-airway collapse.
Some patients with heart failure have obstructive sleep apnea, and some patients with central sleep apnea have no heart failure.
When CSA occurs in the setting of cardiovascular disease, evaluation of the underlying cardiac condition is important.
What Is Cheyne-Stokes Respiration?
Cheyne-Stokes respiration is a form of periodic breathing characterized by a repeating pattern in which ventilation gradually increases and then decreases, often followed by a central apnea or hypopnea.
The pattern may appear approximately as follows:
Breathing increases → breathing decreases → central pause → cycle repeats
It can occur in association with conditions such as heart failure and certain neurologic disorders.
Cheyne-Stokes respiration is more specific than simply saying that a patient had several central apneas.
The overall breathing pattern matters.
Opioids and Central Sleep Apnea
Opioid medications can affect respiratory control during sleep.
In some patients, chronic opioid exposure is associated with central apneas, irregular breathing, hypoventilation, or other forms of sleep-disordered breathing.
The pattern can be complex and may differ from the classic periodic breathing seen in some patients with heart failure.
Medication history is therefore an important part of evaluating central respiratory events.
Patients should not abruptly stop prescribed opioids or other medications based solely on a sleep-study result or internet information.
Medication changes should be discussed with the prescribing clinician.
High Altitude and Central Apneas
Central respiratory events can become more common at altitude.
Reduced oxygen availability stimulates ventilation, which can alter carbon dioxide levels and destabilize respiratory control during sleep.
This can produce periodic breathing and central apneas.
The pattern may improve after acclimatization or returning to a lower altitude, although individual responses vary.
Altitude is therefore an important contextual factor when interpreting a sleep study.
Neurologic Conditions and Central Sleep Apnea
Certain neurologic disorders or injuries can affect respiratory control and contribute to central sleep-disordered breathing.
The specific pattern depends on the location and nature of the neurologic problem.
This is another reason unexplained central events may require broader clinical evaluation rather than simply applying an OSA treatment algorithm.
What Is Treatment-Emergent Central Sleep Apnea?
Some patients undergoing PAP treatment for obstructive sleep apnea develop or continue to have central respiratory events even after their obstructive events have improved.
This is commonly called treatment-emergent central sleep apnea (TECSA).
Historically, the term “complex sleep apnea” has also been used.
In simplified terms:
- The patient initially has predominantly obstructive sleep apnea.
- PAP opens the obstructed airway.
- Obstructive events improve.
- Central events emerge or persist during PAP therapy.
This does not necessarily mean PAP caused a new permanent disease.
Respiratory-control physiology can become more apparent once the obstruction is treated.
Does Treatment-Emergent CSA Always Persist?
No.
Treatment-emergent central sleep apnea can resolve over time in some patients with continued appropriate PAP therapy.
In others, central events persist and may require additional evaluation or a different management strategy.
Factors such as symptoms, residual event frequency, oxygenation, cardiac function, medication use, and the PAP data all matter.
A machine-reported “central” event should also be interpreted cautiously because PAP devices infer event type from airflow and pressure signals rather than measuring respiratory effort in the same way as laboratory polysomnography.
Can CPAP Treat Central Sleep Apnea?
Sometimes, the answer depends on the type of central sleep apnea and the clinical situation.
CPAP is the standard first-line treatment for many patients with obstructive sleep apnea because it splints the upper airway open.
Central sleep apnea is more heterogeneous.
Management may include, depending on the underlying disorder:
- Optimization of an underlying medical condition
- Medication review
- CPAP in selected circumstances
- Other forms of PAP
- Supplemental oxygen in selected patients
- Adaptive servo-ventilation in appropriately selected patients
- Other specialized therapies
There is no single device or pressure setting that should be considered the universal treatment for CSA.
What Is Adaptive Servo-Ventilation?
Adaptive servo-ventilation (ASV) is a specialized form of positive airway pressure that adjusts ventilatory support in response to changes in a patient’s breathing pattern.
ASV may be considered for selected patients with certain forms of central sleep apnea, including some patients with treatment-emergent central sleep apnea.
However, ASV is not appropriate for every patient with central sleep apnea.
The patient’s underlying condition, cardiac function, type of central sleep apnea, symptoms, and other clinical factors should be considered before therapy is selected.
Particular caution is required in patients with heart failure. Evidence regarding ASV has evolved, and recommendations depend on the clinical setting, cardiac function, and the device or treatment strategy being considered.
ASV should therefore be selected through individualized clinical assessment rather than simply because central apneas are present.
That is more durable and avoids implying that the SERVE-HF finding can simply be generalized to every patient, every ASV device, and every heart-failure phenotype.
What About Bilevel PAP?
Bilevel PAP delivers different pressures during inhalation and exhalation.
But the term “bilevel” describes a broad category of therapy.
Different bilevel modes behave differently, and some include a backup respiratory rate while others do not.
Therefore:
“Central apnea = bilevel PAP” is not an appropriate general rule.
The mode must match the respiratory physiology and clinical indication.
Learn more about PAP terminology in CPAP & PAP Therapy.
Does Supplemental Oxygen Treat Central Sleep Apnea?
Supplemental oxygen may be helpful for some types of central sleep apnea or for patients with other oxygen problems.
But oxygen is not interchangeable with PAP, and it is not appropriate for every patient with central events.
The underlying cause, oxygen pattern, ventilation, cardiovascular status, and other factors must be considered.
For more about interpreting overnight oxygen data, see Sleep Apnea and Oxygen Levels: How Low Is Too Low?
Are the Symptoms Different?
Obstructive and central sleep apnea can produce overlapping symptoms.
Possible symptoms include:
- Excessive daytime sleepiness
- Fatigue
- Repeated awakenings
- Poor-quality sleep
- Morning headaches
- Difficulty concentrating
- Witnessed pauses in breathing
Loud snoring is particularly common in obstructive sleep apnea but may not be prominent in central sleep apnea.
Symptoms alone usually cannot reliably determine whether respiratory events are obstructive or central.
Objective testing is often necessary.
Can You Have Both OSA and CSA?
Yes.
Some patients demonstrate both obstructive and central respiratory events.
The proportions may also change under different circumstances, such as the following:
- PAP therapy
- Medication exposure
- Altitude
- Changes in cardiac status
- Changes in sleep stage
- Other physiologic conditions
This is why a sleep-study report should describe the types of respiratory events, not merely provide the overall AHI.
How Are OSA and CSA Diagnosed?
The diagnostic approach depends on the clinical situation.
When central sleep apnea is suspected, comprehensive polysomnography may provide important information because it records sleep along with airflow, respiratory effort, oxygen saturation, cardiac rhythm, and other physiologic signals.
A conventional home sleep apnea test is primarily used to evaluate obstructive sleep apnea in appropriately selected uncomplicated adults and may not adequately characterize more complex central breathing disorders.
For more detail, see Home Sleep Apnea Test vs. Lab Sleep Study: Which One Do You Need?
What Should You Look for on Your Sleep Study?
If your report mentions central events, useful questions include the following:
- What was my overall AHI score?
- How many events were obstructive?
- How many were central?
- What was my central apnea index?
- Were mixed apneas present?
- Was periodic breathing reported?
- Was Cheyne-Stokes respiration described?
- Did central events occur mainly during sleep-wake transitions?
- What happened to my oxygen saturation?
- Do I take medications that can affect breathing?
- Do I have cardiac, neurologic, or other relevant medical conditions?
- Did the central events appear before or after PAP was started?
- Was the test a laboratory polysomnogram or a home study?
- Do the findings meet criteria for a specific central sleep apnea disorder?
Central vs. Obstructive Sleep Apnea: Side-by-Side
| Feature | Obstructive Sleep Apnea | Central Sleep Apnea |
|---|---|---|
| Primary mechanism | Upper-airway narrowing/collapse | Reduced or absent respiratory effort from altered respiratory control |
| Respiratory effort during apnea | Continues | Absent during central event |
| Airflow during apnea | Absent or markedly reduced | Absent or markedly reduced |
| Snoring | Common | May be absent or less prominent |
| Common associations | Upper-airway anatomy, obesity, age and other risk factors | Heart failure, opioids, altitude, neurologic conditions, treatment-emergent CSA, and others |
| Home testing | Useful in appropriately selected uncomplicated adults | Often requires more comprehensive evaluation |
| Treatment approach | PAP, oral appliance, weight management, positional/anatomic therapies as appropriate | Depends strongly on cause; may include treatment of underlying condition, selected PAP modes, oxygen or other therapies |
| One treatment for everyone? | No | No |
The distinction is based on respiratory physiology, not simply on symptoms or whether the person snores.
Why Correct Classification Matters
Obstructive and central apneas may look similar to a bed partner:
The person stops breathing.
But physiologically, they are different events.
Treating upper-airway collapse and treating unstable or absent respiratory drive are not necessarily the same problem.
Correct classification can influence the following:
- Diagnostic evaluation
- Choice of PAP modality
- Medication review
- Cardiac evaluation
- Oxygen assessment
- Follow-up testing
- Other treatment decisions
The Bottom Line
Obstructive and central sleep apnea both involve abnormal breathing during sleep, but the underlying mechanisms differ.
In obstructive sleep apnea, airflow stops or decreases despite continued respiratory effort because the upper airway is narrowed or blocked.
In central sleep apnea, airflow stops or decreases because respiratory effort itself becomes absent or markedly reduced during the event.
Some patients have both patterns, and central events can also emerge during treatment of obstructive sleep apnea.
The most useful question is not simply
“Did I stop breathing?”
It is:
“When breathing stopped, was my body still trying to breathe—and what does that tell us about the underlying mechanism?”
That distinction helps guide the next diagnostic and treatment decisions.
References & Further Reading
- American Academy of Sleep Medicine (AASM). International Classification of Sleep Disorders, Third Edition, Text Revision (ICSD-3-TR). American Academy of Sleep Medicine; 2023.
- Badr MS, Khayat RN, Allam JS, et al. Treatment of central sleep apnea in adults: an American Academy of Sleep Medicine clinical practice guideline. Journal of Clinical Sleep Medicine. 2025;21(12):2181–2191. https://doi.org/10.5664/jcsm.12150
- Javaheri S, Brown LK, Randerath W, Khayat RN. SERVE-HF: more questions than answers. Chest. 2016;149(4):900–904.
https://doi.org/10.1016/j.chest.2015.12.021 - Kapur VK, Auckley DH, Chowdhuri S, et al. Clinical practice guideline for diagnostic testing for adult obstructive sleep apnea. Journal of Clinical Sleep Medicine. 2017;13(3):479–504.
https://doi.org/10.5664/jcsm.6506 - Patil SP, Ayappa IA, Caples SM, et al. Treatment of adult obstructive sleep apnea with positive airway pressure: an American Academy of Sleep Medicine clinical practice guideline. Journal of Clinical Sleep Medicine. 2019;15(2):335–343.
https://doi.org/10.5664/jcsm.7640
Medical Author & Reviewer
Kwaku Osafo-Mensah, MD
Pulmonary Medicine | Sleep Medicine
Diplomate, American Board of Sleep Medicine (ABSM)
More than 20 years of experience in sleep medicineMedically reviewed: August 2026
About the medical reviewer · Editorial Policy
Medical Disclaimer: This information is provided for general educational purposes and is not a substitute for individualized medical evaluation, diagnosis, or treatment. Discuss sleep-study findings, central or obstructive respiratory events, medications, PAP therapy, oxygen therapy, and treatment decisions with a qualified healthcare professional.