There are three main types of sleep apnea: obstructive, central, and mixed (sometimes called complex). Each involves repeated pauses in breathing during sleep, but they happen for different reasons and affect different people. Understanding which type you’re dealing with matters because the causes, risk factors, and treatments vary significantly.
Obstructive Sleep Apnea (OSA)
Obstructive sleep apnea is by far the most common type. It occurs when the muscles in the back of your throat relax too much during sleep, causing the airway to physically narrow or close. Your body still tries to breathe, but air can’t get through. This is what produces the loud snoring, gasping, and choking sounds that bed partners often notice first.
OSA is remarkably widespread. An estimated 83.7 million adults in the United States are living with it, translating to roughly 32% of adults aged 20 and older. Men are affected more often than women, with prevalence rates of about 39% versus 26%. The biggest risk factors include excess weight (especially fat deposits around the upper airway), a naturally narrow throat, a large neck circumference, and older age. Alcohol, sedatives, and sleeping on your back can all worsen it.
During a sleep study, obstructive events are scored by counting how many times per hour your breathing partially or fully stops. This number, called the apnea-hypopnea index (AHI), determines severity in adults:
- Mild: 5 to fewer than 15 events per hour
- Moderate: 15 to fewer than 30 events per hour
- Severe: 30 or more events per hour
Each breathing pause can cause your blood oxygen level to dip. When oxygen saturation drops to 85% or below during the night, it’s associated with significantly higher cardiovascular risk. Over time, untreated OSA raises the likelihood of high blood pressure, heart disease, stroke, and type 2 diabetes, largely because of these repeated oxygen drops and the stress they place on the heart.
Central Sleep Apnea (CSA)
Central sleep apnea is less common and works through a completely different mechanism. Your airway stays open, but your brain temporarily stops sending the signal to breathe. There’s no effort to inhale at all during these pauses, which distinguishes it from obstructive events where the body is actively struggling against a blocked airway.
CSA is closely tied to other medical conditions. Heart failure and stroke are the most common underlying causes. Atrial fibrillation, end-stage kidney disease, and sleeping at high altitude can also trigger it. Certain medications, particularly opioids, are another well-known cause. Men and adults over 60 face higher risk.
The International Classification of Sleep Disorders recognizes six subtypes of central sleep apnea in adults:
- Primary CSA: occurs without an identifiable underlying condition
- Cheyne-Stokes breathing: a distinctive pattern where breathing gradually gets deeper, then shallower, then stops entirely, cycling in roughly 45-second loops. This form is most commonly linked to congestive heart failure or stroke.
- High-altitude CSA: triggered by the lower oxygen levels at elevation
- CSA due to other medical conditions: tied to kidney disease, stroke, or other health problems (outside of Cheyne-Stokes)
- CSA due to drugs or substances: most often caused by opioid pain medications
- Treatment-emergent CSA: central apneas that appear or persist after someone starts CPAP therapy for obstructive sleep apnea
Because CSA often reflects an underlying condition, treatment typically focuses on managing that condition first. Symptoms can overlap with OSA, including excessive daytime sleepiness, morning headaches, and difficulty concentrating. But CSA is less likely to involve loud snoring and more likely to involve abrupt awakenings with shortness of breath or a sensation of not being able to catch your breath.
Mixed (Complex) Sleep Apnea
Mixed sleep apnea combines features of both obstructive and central types. A single breathing pause can start as a central event, with no effort to breathe at all, and then transition into an obstructive event, where the body tries to inhale against a blocked airway. These mixed events show up on sleep studies as a distinct pattern: absent respiratory effort and airflow in the first portion, followed by respiratory effort without airflow in the second.
Complex sleep apnea syndrome, sometimes called CompSAS, is a related concept that often gets grouped under this heading. It describes people who are initially diagnosed with obstructive sleep apnea but develop frequent central apneas once they start CPAP therapy. To qualify for this diagnosis, CPAP must successfully reduce obstructive events to fewer than 5 per hour while central apneas remain at 5 or more per hour. These central events tend to cluster during lighter sleep stages and diminish or disappear during deeper REM sleep.
This pattern affects a meaningful minority of people starting CPAP treatment. For some, the central events resolve on their own within weeks to months as the body adjusts. Others may need a different type of breathing device that automatically adapts to both obstructive and central events.
How Sleep Apnea Differs in Children
Sleep apnea in children is a distinct condition with different causes, symptoms, and diagnostic thresholds. The most common cause of OSA in kids is enlarged tonsils and adenoids, not excess weight. Children with sleep apnea may not snore loudly the way adults do. Instead, parents might notice restless sleep, mouth breathing, bedwetting, or behavioral problems that can mimic ADHD.
The diagnostic bar is also lower. In adults, fewer than 5 breathing events per hour is considered normal. In children, as few as 1 to 2 events per hour can be enough for a diagnosis, though guidelines vary. Severity classifications differ too: mild pediatric OSA is defined as an AHI under 5, moderate between 5 and 10, and severe above 10. These thresholds are significantly lower than adult ranges, reflecting the fact that even a small number of breathing disruptions can affect a child’s development, growth, and behavior.
How the Types Are Told Apart
You can’t reliably distinguish between types based on symptoms alone. Excessive daytime sleepiness, poor concentration, and morning headaches are common across all forms. The only definitive way to determine which type you have is a sleep study, either in a lab or, for obstructive sleep apnea screening, sometimes at home.
During a lab-based study, sensors track airflow, chest and abdominal movement, brain waves, and blood oxygen levels. The key distinction is whether your body is trying to breathe during each pause. In obstructive events, sensors detect chest and abdominal effort even though air isn’t flowing. In central events, the effort itself is absent. Mixed events show the characteristic shift from one pattern to the other within a single pause.
Getting the type right matters for treatment. Standard CPAP, which delivers a constant stream of air pressure to keep the airway open, works well for obstructive sleep apnea but can sometimes worsen central apneas or reveal them for the first time. People with central or complex sleep apnea may need adaptive devices that adjust pressure breath by breath, or treatment focused on the underlying condition driving the central events.