Central sleep apnea is diagnosed primarily through an overnight sleep study called polysomnography, which monitors your breathing, brain activity, and body movements while you sleep. Unlike the more common obstructive sleep apnea, where the airway physically collapses, central sleep apnea happens when your brain temporarily stops sending signals to the muscles that control breathing. That distinction is critical to diagnosis, because the two conditions look very different on a sleep study even though they can feel similar to the person experiencing them.
What Happens During a Sleep Study
Polysomnography (PSG) is the gold standard for diagnosing central sleep apnea. You spend a night in a sleep lab with sensors attached to your scalp, chest, abdomen, and finger. The test records your brain waves, eye movements, heart rhythm, blood oxygen levels, airflow through your nose and mouth, and the rise and fall of your chest and belly as you breathe. A technician monitors the data in real time from another room.
The key measurement is what your chest and abdomen do during pauses in breathing. During normal sleep, your chest and abdomen expand together in sync each time you inhale. During a central apnea event, both stop moving entirely because the brain has paused its breathing signal. There is no airflow and no effort. A central apnea is scored when this complete pause in both airflow and breathing effort lasts at least 10 seconds.
This is what separates central from obstructive events. In obstructive sleep apnea, the airway is blocked but the body keeps trying to breathe. The chest and abdomen move out of sync, pulling in opposite directions as the diaphragm pushes against a closed throat. In central sleep apnea, the body simply isn’t trying. That absence of effort is the defining signal on the sleep study.
The Numbers That Confirm a Diagnosis
A single pause in breathing doesn’t mean you have central sleep apnea. Clinicians look at the central apnea index, which counts how many central apnea or central hypopnea events occur per hour of sleep. In adults, a count of five or more central events per hour is considered clinically significant.
There’s a second requirement: more than 50% of all respiratory events recorded during the study must be central in nature, not obstructive. Many people have a mix of both types, and if most events involve airway obstruction rather than absent effort, the diagnosis tips toward obstructive sleep apnea instead. For a primary central sleep apnea diagnosis, you also need at least one symptom of disrupted sleep, such as daytime sleepiness, insomnia, waking up short of breath, snoring, or a bed partner witnessing pauses in your breathing.
Why Home Sleep Tests Don’t Work for This
Home sleep apnea tests are widely used to screen for obstructive sleep apnea, but they are not recommended when central sleep apnea is the primary concern. These portable devices have not been cleared for detecting central events. They typically lack the brain wave monitoring (EEG) needed to accurately measure total sleep time and sleep stages, and they can’t reliably distinguish between central and obstructive hypopneas, which are partial reductions in breathing that fall short of a full pause.
If your doctor suspects central sleep apnea based on your symptoms or medical history, particularly if you have heart failure, a history of stroke, neuromuscular disease, or chronic opioid use, an in-lab polysomnography is the appropriate test. The lab setting also allows for more precise respiratory effort monitoring, sometimes including an esophageal pressure sensor that removes any ambiguity about whether breathing effort was present during an event.
The Challenge of Hypopneas
Not every breathing disruption is a complete pause. Hypopneas, which are partial reductions in airflow, are common in both central and obstructive sleep apnea, and telling them apart can be genuinely difficult. In an obstructive hypopnea, chest and abdomen movements fall out of sync partway through the event as the body strains against a narrowed airway. In a central hypopnea, chest and abdomen movements stay in sync but gradually shrink together as breathing drive fades, then gradually return as drive recovers. This creates a smooth waxing-and-waning pattern rather than the jerky, opposing movements of obstruction.
Even with laboratory-grade equipment, the true nature of hypopneas can be hard to classify with confidence. The AASM acknowledges that in patients whose events are predominantly hypopneas rather than full apneas, distinguishing central from obstructive breathing disorders is challenging without esophageal pressure monitoring, which directly measures the effort generated inside the chest.
Subtypes Your Doctor May Identify
Central sleep apnea isn’t a single condition. The current classification system recognizes six subtypes, and the sleep study helps determine which one applies to you.
- Primary central sleep apnea meets the standard criteria (five or more central events per hour, more than half of events central) without an identifiable underlying cause like heart failure or medication use.
- Central sleep apnea with Cheyne-Stokes respiration shows a distinctive crescendo-decrescendo breathing pattern: breaths get progressively deeper, then progressively shallower, then stop entirely before the cycle repeats. To qualify, the sleep study must show at least three consecutive central apneas or hypopneas separated by this waxing-waning pattern, with each full cycle lasting at least 40 seconds (typically 45 to 90 seconds). At least five such events per hour must be recorded over a minimum of two hours. This pattern is closely associated with heart failure.
- Central sleep apnea due to a medication or substance is commonly linked to opioid use. Opioids can cause central apneas, irregular breathing patterns, and sustained periods of shallow breathing during sleep. Your medication history is an essential part of the diagnostic workup.
- Central sleep apnea due to a medical disorder (without Cheyne-Stokes) covers cases caused by conditions like stroke, kidney failure, or brainstem lesions that affect respiratory control.
- Treatment-emergent central sleep apnea is diagnosed when someone being treated for obstructive sleep apnea with a CPAP or similar device has their obstructive events resolve, only for central apneas to appear or persist. This requires a follow-up titration study to detect.
- Central sleep apnea due to high altitude occurs from the body’s response to lower oxygen levels at elevation.
What Leads to Testing in the First Place
Central sleep apnea often doesn’t announce itself the way obstructive sleep apnea does. Loud snoring, the hallmark of obstructive apnea, may be mild or absent. Instead, the symptoms tend to be subtler: fragmented sleep, waking up frequently during the night, excessive daytime sleepiness, difficulty concentrating, or a bed partner noticing that your breathing stops and starts without the gasping or choking that typically follows an obstructive event.
Doctors are more likely to order a sleep study specifically looking for central sleep apnea if you have heart failure, a neurological condition affecting the brainstem, or you take opioid medications long-term. In these populations, the risk of central events is high enough that screening is part of routine care. If you’ve already been diagnosed with obstructive sleep apnea and your symptoms aren’t improving with CPAP therapy, that’s another common trigger for re-evaluation, since treatment-emergent central sleep apnea may be developing.