Sleep apnea is a condition where your breathing repeatedly stops and restarts while you sleep. These pauses can happen dozens or even hundreds of times per night, each one lasting long enough to drop your blood oxygen levels and pull you out of deep sleep. Roughly one in three adults has at least a mild form, and many don’t know it.
How Sleep Apnea Works
The word “apnea” comes from Greek and literally means “without breath.” In practice, it refers to any pause in breathing that lasts 10 seconds or longer during sleep. A related event called a hypopnea is a partial reduction in airflow rather than a complete stop. Both count when measuring how severe someone’s sleep apnea is.
Each time breathing pauses, oxygen levels in the blood dip. The brain detects the drop and triggers a brief arousal, just enough to reopen the airway or restart the breathing signal. You rarely wake up fully, so you may have no memory of these interruptions. But the cumulative effect is significant: your body never settles into the sustained deep sleep it needs to repair tissues, regulate hormones, and consolidate memory.
Three Types of Sleep Apnea
Obstructive sleep apnea (OSA) is by far the most common. It happens when the muscles in the back of your throat relax too much during sleep, causing the soft tissue to collapse inward and physically block the airway. Fat deposits around the upper airway can make the obstruction worse, which is one reason excess weight is the single biggest risk factor. A thick neck, a naturally narrow airway, or a recessed jaw all increase the odds.
Central sleep apnea is less common and works differently. The airway stays open, but the brain temporarily fails to send the right signals to the muscles that control breathing. This form is more closely tied to heart failure, stroke, and opioid use. One recognizable pattern, called Cheyne-Stokes breathing, involves a cycle where breaths gradually get deeper and then shallower until they stop entirely for a few seconds before the cycle repeats.
Treatment-emergent (complex) sleep apnea is a combination: someone initially diagnosed with obstructive sleep apnea begins showing central apnea events once the physical obstruction is treated. It’s the rarest of the three.
Symptoms That Point to Sleep Apnea
Loud, chronic snoring is the hallmark, especially snoring that includes gasping or choking sounds. But not everyone who snores has sleep apnea, and not everyone with sleep apnea snores loudly. Other nighttime signs include restless sleep, waking up with a dry mouth or sore throat, and frequent trips to the bathroom.
Daytime symptoms are often what finally push people to seek answers. Excessive sleepiness despite what seemed like a full night’s rest, morning headaches, difficulty concentrating, and irritability are all common. Some people notice their memory or decision-making has gotten worse over months or years without an obvious explanation.
Symptoms in Children
Sleep apnea looks different in kids. Rather than daytime sleepiness, children with sleep apnea tend to show behavioral problems: hyperactivity, impulsiveness, aggression, and trouble paying attention in school. These symptoms overlap with ADHD, which means pediatric sleep apnea sometimes gets misdiagnosed. The most common cause in children is enlarged tonsils and adenoids rather than excess weight.
How Severity Is Measured
Doctors use a number called the apnea-hypopnea index, or AHI, which counts how many times your breathing stops or significantly drops per hour of sleep. According to Harvard Medical School’s classification:
- Normal: fewer than 5 events per hour
- Mild: 5 to 14 events per hour
- Moderate: 15 to 29 events per hour
- Severe: 30 or more events per hour
Someone with severe sleep apnea is experiencing a breathing disruption every two minutes, on average, throughout the night. Even mild sleep apnea can cause noticeable daytime fatigue if the events cluster during the deeper stages of sleep.
How It Affects the Rest of Your Body
Sleep apnea is not just a sleep problem. The repeated drops in oxygen trigger a chain of stress responses that reach well beyond the throat.
Each apnea episode floods the nervous system with stress hormones, raising heart rate and blood pressure. Over time, this leads to sustained high blood pressure, even during waking hours. The American Heart Association has identified obstructive sleep apnea as an independent risk factor for heart failure, coronary artery disease, irregular heart rhythms, and stroke. The connection to stroke, in particular, goes beyond what high blood pressure alone would explain: the repeated oxygen drops appear to promote blood clotting and damage blood vessel walls directly.
Sleep apnea also disrupts how the body handles blood sugar. Fragmented sleep and low oxygen increase cortisol and inflammatory markers, both of which make cells less responsive to insulin. Research in healthy young adults has shown that experimentally fragmenting sleep, even for a few nights, measurably reduces insulin sensitivity. For people who already have type 2 diabetes, untreated sleep apnea makes blood sugar harder to control.
How Sleep Apnea Is Diagnosed
The gold standard is an overnight sleep study, called polysomnography, done in a sleep lab. Sensors track brain waves, eye movement, heart rhythm, blood oxygen, breathing effort, leg movements, chin muscle activity, and body position. The combination lets technicians identify not just apnea events but also what stage of sleep you’re in when they happen and whether your body position plays a role.
For many people, a home sleep test is a simpler first step. These portable devices typically measure blood oxygen, chest movement, nasal airflow, and sometimes blood volume in small arteries. They’re effective at confirming moderate to severe obstructive sleep apnea but can miss milder cases or central sleep apnea because they don’t track brain activity or sleep stages. If a home test comes back normal but symptoms persist, an in-lab study is usually the next step.
Treatment Options
The most widely prescribed treatment is a CPAP machine (continuous positive airway pressure). It delivers a steady stream of pressurized air through a mask you wear while sleeping, keeping the airway from collapsing. The pressure level is either set to a fixed number based on a calibration study or, with an auto-adjusting version (APAP), the machine raises and lowers pressure throughout the night in response to your breathing patterns. Most people notice a dramatic improvement in daytime alertness within the first week or two of consistent use.
A bilevel machine (BiPAP) delivers higher pressure when you inhale and lower pressure when you exhale. It’s sometimes used when standard CPAP feels uncomfortable or when someone also has trouble fully exhaling, but studies generally show no clear advantage over CPAP for straightforward obstructive sleep apnea.
For people with mild to moderate sleep apnea who can’t tolerate a CPAP, a custom-fitted oral appliance is an alternative. These devices push the lower jaw slightly forward to keep the airway open. They don’t reduce apnea events as much as CPAP does, but people tend to wear them more consistently. Studies show that the actual improvements in daytime sleepiness and quality of life often end up comparable because nightly adherence is higher.
Weight loss can significantly reduce or even resolve obstructive sleep apnea in people who are overweight, since fat deposits around the airway are a primary contributor. Positional therapy (training yourself to sleep on your side rather than your back) helps a subset of people whose apnea is position-dependent. In children, surgical removal of enlarged tonsils and adenoids is the most common and effective treatment.