An apnea is a pause in breathing that lasts at least 10 seconds. It can happen during sleep, under anesthesia, or in newborns whose breathing control is still developing, but the vast majority of people searching this term are encountering it in the context of sleep apnea, a condition where breathing repeatedly stops and restarts throughout the night. An estimated 83.7 million adults in the United States have some form of obstructive sleep apnea, translating to roughly 32% of adults over age 20.
What Happens During an Apnea Event
Clinically, a single apnea event is scored when airflow drops by 90% or more from its baseline level and stays that low for at least 10 seconds. During that pause, oxygen levels in the blood dip while carbon dioxide builds up. The brain detects this shift and triggers a brief arousal, just enough to restart breathing. Most people don’t fully wake up during these arousals, so they have no memory of them in the morning. But the cycle can repeat dozens or even hundreds of times per night, fragmenting sleep and starving the body of steady oxygen.
Three Types of Sleep Apnea
Not all apneas have the same cause. The type determines both what’s going wrong and how it’s treated.
Obstructive Sleep Apnea
This is by far the most common type. The muscles in the back of the throat relax too much during sleep, and the soft tissue collapses inward, physically blocking the airway. Your lungs are still trying to breathe, but air can’t get through. Risk factors include excess weight (especially around the neck), a naturally narrow airway, and sleeping on your back. Men are affected more often than women: prevalence is about 39% in males compared to 26% in females.
Central Sleep Apnea
In central sleep apnea, the airway stays open, but the brain temporarily stops sending the signal to breathe. This reflects a malfunction in the body’s chemical sensors that monitor oxygen and carbon dioxide levels. It often appears in people with heart failure, stroke, or conditions affecting the brainstem. A hallmark pattern is breathing that gradually swells and fades in a rhythmic cycle, sometimes called Cheyne-Stokes respiration.
Complex Sleep Apnea
Some people have both problems at once: a collapsing airway and unstable breathing signals from the brain. This is called complex sleep apnea. It’s sometimes discovered when someone starts treatment for obstructive apnea and central events emerge once the physical blockage is resolved.
Symptoms Beyond Snoring
Loud snoring is the symptom most people associate with sleep apnea, but it’s far from the only one. Waking up gasping or feeling like you’re choking is common. So is excessive daytime sleepiness, the kind where you struggle to stay awake during meetings or while driving, not just feeling a little tired.
Less obvious signs include morning headaches, difficulty concentrating, memory problems, and mood changes like irritability or depression. Some people notice they’re getting up to urinate multiple times per night. Because these symptoms overlap with so many other conditions, sleep apnea often goes unrecognized for years. One case report described a young patient with severe sleep fragmentation whose primary complaints were fatigue, poor concentration, and declining academic performance, not snoring.
How Apnea Severity Is Measured
Doctors quantify sleep apnea using the Apnea-Hypopnea Index, or AHI, which counts the number of apnea and partial-blockage events per hour of sleep. The severity breakdown is straightforward:
- Mild: 5 to 14 events per hour
- Moderate: 15 to 30 events per hour
- Severe: more than 30 events per hour
Among people with obstructive sleep apnea, about 52% fall in the mild category, 30% are moderate, and 18% are severe. Even mild cases can cause meaningful daytime sleepiness and long-term health effects, particularly if left untreated for years.
How It Damages the Body Over Time
The repeated oxygen drops from apnea, called intermittent hypoxia, set off a cascade of stress responses that extend far beyond poor sleep. Each breathing pause triggers a burst of adrenaline-like hormones as the nervous system jolts the body awake. Over weeks and months, this chronic activation raises blood pressure. Animal studies show that blood pressure starts climbing within 5 to 8 days of intermittent oxygen deprivation and stays elevated even after normal breathing is restored.
The blood vessel lining also takes damage. Intermittent hypoxia impairs the vessels’ ability to relax and dilate properly while increasing constriction. Over time, this promotes thickening of artery walls and accelerates plaque buildup, the process behind atherosclerosis. The inflammatory response adds fuel: the body’s master inflammatory switch activates, driving chronic low-grade inflammation throughout the cardiovascular system.
The heart itself is affected. Untreated apnea increases susceptibility to heart attacks, enlarges infarct size if one occurs, and promotes structural changes in the heart, including thickening of the heart walls, scarring, and reduced pumping capacity. These pathways help explain why sleep apnea is strongly linked to heart failure, stroke, atrial fibrillation, type 2 diabetes, and metabolic syndrome.
Getting Diagnosed
The gold standard for diagnosing sleep apnea is an overnight sleep study called polysomnography, performed in a sleep lab. It tracks brain waves, eye movements, muscle activity, heart rhythm, breathing effort, airflow, and oxygen levels simultaneously. This gives the most complete picture and can distinguish between obstructive and central apnea.
Home sleep tests are a simpler alternative that measure basic respiratory and oxygen parameters using a portable device you wear to bed. They’re less comprehensive and results can be more variable, but they make diagnosis far more accessible, especially for people who can’t easily spend a night in a sleep lab. Home tests work best when obstructive sleep apnea is the suspected diagnosis and there are no other significant sleep or breathing conditions complicating the picture.
Treatment Options and How Well They Work
CPAP (continuous positive airway pressure) remains the most effective treatment. It delivers a steady stream of pressurized air through a mask, holding the airway open throughout the night. On average, CPAP reduces apnea events by about 31 per hour, a substantial improvement for moderate and severe cases. It also significantly reduces daytime sleepiness. The main challenge is consistency: some people find the mask uncomfortable or struggle to use it every night.
Oral appliances, sometimes called mandibular advancement devices, are custom-fitted mouthpieces that push the lower jaw slightly forward to keep the airway open. They reduce apnea events by roughly 12 per hour. That’s less effective than CPAP on paper, but for people with mild to moderate apnea who won’t tolerate a mask, they can be a practical alternative that actually gets used.
A newer option is hypoglossal nerve stimulation, a surgically implanted device that stimulates the nerve controlling tongue movement, preventing the tongue from falling back and blocking the airway during sleep. It reduces events by about 11 per hour and meaningfully improves daytime sleepiness. It’s typically reserved for people who haven’t succeeded with CPAP.
Myofunctional therapy, a set of exercises that strengthen the muscles of the mouth and throat, has also shown significant reductions in sleepiness scores. Weight loss, positional therapy (avoiding sleeping on your back), and avoiding alcohol before bed are behavioral strategies that can reduce apnea severity, particularly in milder cases.