The two types of sleep apnea are obstructive sleep apnea (OSA) and central sleep apnea (CSA). Both cause repeated pauses in breathing during sleep, but they happen for completely different reasons. OSA is by far the more common type, affecting roughly 32% of U.S. adults, while CSA is relatively rare and usually linked to other medical conditions like heart failure or stroke.
Obstructive Sleep Apnea: A Physical Blockage
Obstructive sleep apnea happens when the muscles in the back of your throat relax too much while you sleep. These muscles support the soft palate, the tongue, and the walls of the throat. When they go slack, the airway narrows or closes entirely as you breathe in. Your body briefly stops getting air, oxygen levels in the blood drop, and carbon dioxide builds up until your brain jolts you awake just enough to reopen the airway. This cycle can repeat dozens or even hundreds of times per night.
The hallmark symptom of OSA is loud, chronic snoring, often punctuated by choking or gasping sounds. Bed partners usually notice the problem before the person with OSA does. Daytime sleepiness, morning headaches, difficulty concentrating, and irritability are common because sleep is constantly fragmented, even if you don’t remember waking up.
OSA is strongly tied to body weight. Excess tissue around the neck and throat makes the airway more likely to collapse. But anatomy plays a role too: a naturally narrow airway, enlarged tonsils, or a recessed jaw all raise the risk. Men are significantly more likely to develop OSA than women, with prevalence around 39% in males compared to 26% in females. The condition becomes more common with age as muscle tone naturally decreases.
Central Sleep Apnea: A Signaling Problem
Central sleep apnea has nothing to do with a blocked airway. Instead, the brain temporarily stops sending signals to the muscles that control breathing. The part of the brainstem responsible for regulating heart rate and respiration simply fails to tell your body to inhale. You don’t struggle against a closed airway. You just stop breathing because the instruction never arrives.
CSA is far less common than OSA and tends to show up alongside other serious health conditions. Heart failure is the strongest association: about 4.8% of people with heart failure have CSA. Stroke, neurological diseases, and chronic use of opioid medications also increase risk. Like OSA, it is more common in men and in older adults. One characteristic breathing pattern seen in CSA is a gradual rise and fall in breathing effort, where airflow slowly builds, peaks, fades, and then stops altogether before the cycle restarts.
The symptoms overlap quite a bit with OSA: daytime fatigue, poor sleep quality, and difficulty concentrating. But people with CSA are less likely to snore loudly and more likely to notice shortness of breath or a sensation of breathlessness when they wake during the night. Because CSA is often driven by an underlying condition, treating that condition is a central part of managing it.
How the Two Types Are Diagnosed
Both types are diagnosed with a sleep study, either in a sleep lab or with a home testing device. The study tracks how many times per hour your breathing stops or becomes dangerously shallow. This number is called the apnea-hypopnea index, or AHI. Harvard Medical School classifies severity on a simple scale:
- Mild: 5 to 14 events per hour
- Moderate: 15 to 29 events per hour
- Severe: 30 or more events per hour
Fewer than 5 events per hour is considered normal. The sleep study also reveals whether the pauses are obstructive (you’re trying to breathe but can’t) or central (your body makes no effort to breathe at all), which is how doctors distinguish between the two types.
Treatment Differs Between Types
For obstructive sleep apnea, the standard treatment is a CPAP machine, which delivers a steady stream of air pressure through a mask to keep the airway open while you sleep. Weight loss, positional therapy (sleeping on your side), and oral appliances that reposition the jaw can also help in milder cases. For more severe OSA, CPAP remains the most effective option.
Central sleep apnea is trickier to treat because the problem originates in the brain rather than the throat. CPAP alone often isn’t enough. In fact, some patients with CSA do poorly on standard CPAP because the steady pressure doesn’t address the underlying signaling issue. A more advanced device called adaptive servo-ventilation (ASV) monitors breathing patterns in real time and adjusts air pressure breath by breath to fill in the gaps when the brain fails to trigger an inhale. Research published by the European Respiratory Society found ASV effective at controlling both the breathing pauses and the symptoms in patients whose central apnea didn’t respond to CPAP.
Addressing the root cause matters too. If CSA is driven by heart failure, optimizing heart treatment can reduce or resolve the apnea. If opioid medications are the trigger, adjusting the medication regimen with a doctor may be necessary.
When Both Types Occur Together
Some people have what’s known as complex sleep apnea syndrome, where treatment for obstructive sleep apnea unmasks central apnea that wasn’t previously apparent. This typically happens when someone starts CPAP therapy: the machine successfully eliminates the airway collapse, but central breathing pauses emerge or become more frequent.
The leading explanation involves carbon dioxide levels. When CPAP opens the airway and improves gas exchange, blood CO2 can drop below the threshold that triggers the brain’s breathing reflex. Without that chemical nudge, the brain temporarily stops initiating breaths. A second theory points to over-pressurization: if the CPAP pressure is set too high, stretch receptors in the lungs send signals that inhibit the breathing center, essentially telling the brain to pause inhalation as a protective reflex against overinflation.
Complex sleep apnea is managed by carefully adjusting CPAP pressure to avoid over-correction, sometimes deliberately allowing a mild degree of airway resistance to keep the brain’s breathing drive intact. When that approach isn’t enough, adaptive servo-ventilation is the typical next step.