Central Sleep Apnea: How It Differs From Obstructive Apnea

In obstructive apnea, the body tries to breathe through a closed passage. In central apnea, the passage may be open—but the command to breathe briefly fades. The pause looks similar from the outside, yet the failure begins in a different place.

Central sleep apnea (CSA) is a sleep-related breathing disorder in which airflow repeatedly stops or falls because respiratory effort itself pauses. That is the defining difference from obstructive sleep apnea, where the chest and abdomen continue working while the upper airway narrows or closes.

The distinction matters because CSA is not one single disease. It can appear with heart failure, high altitude, opioid or other medication exposure, neurological or medical conditions, or treatment for obstructive apnea. Identifying the cause is part of the diagnosis, not an optional detail added afterward.

Central vs. Obstructive Apnea: What Actually Stops?

Breathing depends on two separate systems working together. The brainstem must generate a respiratory drive, and the airway must remain open enough for air to move. Obstructive apnea mainly disrupts the second system. Central apnea mainly disrupts the first.

During an obstructive event, airflow falls but breathing effort continues. During a central event, airflow and respiratory effort fall together. A 2025 interdisciplinary review of adult CSA describes two broad mechanisms: unstable feedback control that repeatedly overshoots and undershoots, and reduced respiratory drive from brainstem dysfunction, medication effects, or other conditions.

Why Does the Breathing Signal Pause?

One common pathway is an overly sensitive feedback loop. Breathing removes carbon dioxide from the blood. If ventilation briefly overshoots, carbon dioxide can fall below the level that normally sustains breathing during sleep. Respiratory effort then pauses until carbon dioxide rises again. The resulting cycle can produce alternating stronger breathing and central pauses.

This pattern is especially important in heart failure and at high altitude. Some people with heart failure develop Cheyne–Stokes breathing: a repeating rise and fall in breathing depth separated by central events. At altitude, low oxygen stimulates faster breathing, which lowers carbon dioxide and can destabilize the sleeping control system.

A different pathway is depressed respiratory drive. Opioids are a well-known cause because they can suppress brainstem breathing control. A 2024 review of medication-induced CSA also discusses several less familiar medication associations. A complete medication and substance history matters because an exposure-related pattern can otherwise be mislabelled as unexplained or “primary” CSA.

The Main Central Sleep Apnea Patterns

CSA associated with heart failure often reflects unstable ventilatory control and may appear with Cheyne–Stokes breathing. High-altitude CSA can emerge after ascent and may improve after acclimatization or descent. Medication- or substance-induced CSA is most strongly associated with opioids, although other drugs may contribute.

CSA due to another medical or neurological condition can occur when disease affects breathing control or respiratory muscles. Primary CSA is diagnosed only when a clearer cause is not found.

Treatment-emergent central sleep apnea appears when obstructive events improve during positive-airway-pressure treatment but central events emerge or remain. This does not mean CPAP “damaged” breathing. Removing obstruction can reveal an unstable control system that was previously hidden inside the mixed pattern.

Does Treatment-Emergent CSA Go Away?

Often, but not always. A systematic review of its natural history found that most treatment-emergent central events resolved over weeks to months, while a substantial minority persisted or appeared later. The practical response is follow-up, not immediate abandonment of treatment or unsupervised changes to pressure settings.

Mask leak, repeated awakenings, excessive pressure, heart disease, medication exposure, and the original severity of obstructive apnea can all affect what appears on the machine report. Device estimates are useful for trends, but they are not as reliable as a properly interpreted sleep study for deciding whether an event is truly central.

What Symptoms Does Central Sleep Apnea Cause?

CSA can cause repeated awakenings, insomnia-like difficulty, unrefreshing sleep, morning headache, fatigue, poor concentration, and excessive daytime sleepiness. Some people wake short of breath. Others notice very little and are identified because of heart failure, opioid treatment, altitude exposure, or a sleep study performed for another reason.

Loud snoring is less central to the pattern than it is in OSA, but the two disorders can coexist. A partner may notice pauses followed by deeper breathing rather than obvious choking against a blocked airway. Symptoms still cannot determine the type without measuring effort.

Waking cognitive tests can show that attention or reaction time is worse, but they cannot tell whether the cause is CSA, OSA, insufficient sleep, medication, or something else. CT’s free brain tests collection measures waking performance rather than breathing during sleep.

How Is Central Sleep Apnea Diagnosed?

Laboratory polysomnography is the most informative test because it records airflow and breathing effort together, along with oxygen, brain activity, heart rhythm, sleep stage, and arousals. The effort channels are what separate a central pause from an obstructive one.

Home sleep apnea testing is designed mainly for selected adults with suspected uncomplicated OSA. The AASM diagnostic guideline recommends laboratory testing when heart or lung disease, neuromuscular weakness, chronic opioid use, suspected hypoventilation, stroke history, or severe insomnia complicates the picture. Those are also situations in which central events may be more relevant.

The report includes the total apnea-hypopnea index, but clinicians also examine how many events are central, when they occur, whether breathing waxes and wanes, how oxygen changes, and what conditions or medications could explain the pattern. A high event count alone does not identify the mechanism.

Why Treatment Is More Complicated Than “Use CPAP”

The 2025 AASM clinical guideline for adult CSA treatment begins with a good-practice principle: optimize the condition contributing to central events and judge treatment by symptoms and quality of life, not only by whether every event disappears.

Depending on the cause, options may include continuous positive airway pressure, bilevel pressure with a backup breathing rate, adaptive servo-ventilation, low-flow oxygen, acetazolamide, or transvenous phrenic-nerve stimulation. These are conditional, cause-specific options—not a ladder that everyone climbs in the same order.

The details matter. Bilevel pressure without a backup rate can worsen some central patterns and is not recommended as a general CSA treatment. Adaptive servo-ventilation may be considered for several CSA types, but the AASM advises experienced-center use with close monitoring in heart failure with reduced ejection fraction. Phrenic-nerve stimulation is invasive, costly, and generally considered after less invasive options.

What to Bring to an Evaluation

Bring the sleep-study report if one exists, not only the headline AHI. List heart, lung, neurological, and kidney conditions; recent altitude exposure; and every medication or substance that can affect breathing, especially opioids. Note whether central events appeared before treatment or only after PAP began.

Also record sleep and wake times, awakenings, breathlessness, daytime dozing, and any partner-observed waxing-and-waning breathing for two weeks. This history helps connect the laboratory pattern with the condition that may be driving it.

An Open Airway Does Not Guarantee a Breath

Central sleep apnea is different from obstruction because the respiratory command and effort pause together. The airway may remain open, yet airflow still stops. That difference changes the likely causes, the testing needed, and the treatment choices.

Continue through the Sleep section or return to the broader sleep-disorders guide to compare breathing disorders with insomnia, circadian conditions, parasomnias, and movement disorders. Cognitive Train’s wider brain training and cognitive testing library focuses on waking abilities; sleep-study signals answer the breathing question.