Sleep Apnea: Types, Causes, Symptoms & Treatment

Sleep apnea is a breathing disorder causing brief interruptions of breathing during sleep. The involuntary breathing pauses are called apneic events. This happens either because of blockage of your airway (obstructive sleep apnea) or because your brain doesn’t correctly control your breathing (central apnea).

During the apneic event, you can’t breathe in oxygen or exhale carbon dioxide. This results in low levels of oxygen and increased levels of carbon dioxide in the blood. This alerts the brain to resume breathing and cause an arousal. With each arousal, a signal is sent from the brain to the upper airway muscles to open the airway. Breathing is resumed, often with a loud snort or gasp. Frequent arousals, although necessary for breathing to restart, prevent restorative, deep sleep.

The resulting lack of oxygen activates a survival reflex that wakes you up just enough to resume breathing. While that reflex keeps you alive, it also interrupts your sleep cycle. That prevents restful sleep and can have other effects, including putting stress on your heart that can have potentially deadly consequences.

Sleep apnea is uncommon but widespread. Experts estimate it affects about 5% to 10% of people worldwide. It is a long-term, chronic condition. For some people, it’s possible to resolve it by reducing their weight or undergoing certain treatments. For others, it may be a lifelong condition.

Many health conditions are linked to sleep apnea, including obesity, Irregular heartbeat, Heart attack, Stroke and high blood pressure. These conditions, coupled with the lack of sleep, can harm many different systems in your body. It does more than make you sleepy. When left untreated, it can contribute to heart disease, diabetes, and other long-term health risks.

Key points about sleep apnea

• Sleep apnea is a breathing disorder that causes brief times when you stop breathing during sleep.
• There are three types of sleep apnea: central sleep apnea, obstructive sleep apnea, and complex/mixed sleep apnea.
• Sleep apnea seems to run in some families, suggesting a possible hereditary basis.
• Diagnosis of sleep apnea is not simple because there can be many different causes.
• Treatment may involve behavioral changes, weight loss, CPAP therapy, and sometimes surgery.

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Types of sleep apnea

The main types of sleep apnea are:

• Obstructive sleep apnea (OSA). This is the more common form that occurs when throat muscles relax and block the flow of air into the lungs
• Central sleep apnea (CSA). This occurs when the brain doesn’t send proper signals to the muscles that control breathing
• Mixed/Complex sleep apnea or Treatment-emergent central sleep apnea. This happens when someone has OSA, diagnosed with a sleep study, that converts to CSA when receiving therapy for OSA

To understand how sleep apnea works, it helps to know a little bit about the human sleep cycle. Sleep happens in multiple stages:

• Stage 1: Light sleep. This is a short stage that begins right after you fall asleep. It accounts for about 5% of your total sleep time.
• Stage 2: Deeper sleep. This stage is deeper and makes up about 45% to 50% of all the time you spend sleeping (this number goes up as you get older).
• Stage 3: Slow wave sleep. This is the deepest sleep stage, making up about 25% of the time you spend sleeping (this number goes down with age). It’s very hard to wake someone up in stage 3 sleep, and waking up directly from it usually causes “sleep inertia,” a state of “mental fog” and slowed thinking. Parasomnias like sleepwalking and sleeptalking happen in this stage.
• REM sleep: REM stands for “rapid eye movement.” This stage is when you dream. When a person is in REM sleep, you can see their eyes moving beneath their eyelids.

When you fall asleep, you typically enter Stage 1, and then move into and cycle between Stages 2 and 3. After cycling between those stages, you’ll ultimately go into REM sleep and start dreaming. After the first REM cycle, you start a new cycle and go back into Stage 1 or 2. One cycle normally takes about 90 to 110 minutes before another begins. Most people go through four or five cycles per night (assuming they get a full eight hours of sleep).

How sleep apnea disrupts your sleep cycle

Your brain constantly monitors your body’s status and adjusts your heart rate, blood pressure, breathing, etc. Your blood oxygen levels can drop when you stop breathing because of either apnea or hypopnea.

• Apnea: This is when you stop breathing while asleep or have almost no airflow. It combines the Greek roots “a,” which means “not” and “pnea,” which refers to breathing. Combined, it means “breathless.”
• Hypopnea: This combines Greek word roots “hypo” and “pnea.” The root “hypo” means “low” or “under.” Combining these root words means “under-breathing” or “low breathing,” which means you aren’t breathing enough to maintain oxygen levels in your blood.

Your brain reacts to blood oxygen drops, from either apnea or hypopnea, by triggering a failsafe-like reflex, waking you up enough for you to breathe again. Once you resume breathing, your brain automatically tries to resume your sleep cycle.

Stages of sleep apnea

The more severe your sleep apnea is, the more often you’ll see these interruptions happen. The apnea/hypopnea index (AHI) is the average hourly number of apnea or hypopnea events, times when a person stops breathing. The AHI is the main factor determining the severity of sleep apnea. The severity is as follows:

• Mild sleep apnea: This level means a person has an AHI between 5 and 15. That means they have between 5 and 15 apnea or hypopnea events per hour. However, healthcare providers also consider symptoms at this level. If you don’t have other symptoms, they may not consider it severe enough to treat.
• Moderate sleep apnea: People with moderate sleep apnea have between 15 and 29 events per hour. That means a person who sleeps eight hours stops breathing and/or wakes up between 120 and 239 times.
• Severe sleep apnea: People with severe sleep apnea wake up 30 or more times in an hour. That means they stop breathing and/or wake up 240 times or more during a full eight hours of sleep.

Obstructive events, which are very short-lived, can affect any stage of sleep. They’re most common in Stage 1, Stage 2 and REM sleep. That’s why it’s common for people to not remember apnea events, which means they may not know they have a problem until the symptoms are noticeable. Central events are most common in Stages 1 and 2 of sleep but can occur during any stage.

Types and stages of sinusitis (sinus infection)

Symptoms of sleep apnea

The symptoms of obstructive and central sleep apneas overlap, sometimes making it difficult to determine which type you have. The most common symptoms of obstructive and central sleep apneas include:

• Feeling tired or even exhausted when waking up. Even after a full night’s sleep, people with sleep apnea commonly feel extremely tired.
• Daytime sleepiness. In more severe cases, this can cause drowsiness during driving, working or other activities.
• Snoring. This is a common feature with sleep apnea (but it isn’t something that happens in all cases). You can also have sleep apnea without snoring at all.
• Mood changes. Depression and anxiety are common symptoms of sleep apnea.
• Disruptions in brain function. These can include memory loss, trouble concentrating or other brain-related issues.
• Waking up repeatedly in the middle of the night. This symptom might be harder to notice because people usually don’t remember waking up or why they woke up. People who do this often remember waking up for another reason, like heartburn or needing to go to the bathroom.
• Pauses in breathing while asleep that others witness. A spouse, partner or other loved one may notice these symptoms while you’re asleep.
• Unusual breathing patterns. Cheyne-Stokes breathing (CSB) is a distinctive breathing pattern that can happen with central sleep apnea. CSB causes fast breathing that gets deeper and then shallower again until breathing stops altogether. After not breathing for several seconds, they’ll start breathing again, then, starting the pattern all over again.
• Insomnia.
• Night sweats and feeling restless at night.
• Sexual dysfunction.
• Waking up feeling short of breath or like you’re choking.
• Headaches, especially when waking up.

Sleep apnea in children can happen in slightly different ways. The symptoms of sleep apnea in children include:

• Hyperactivity or trouble focusing or performing poorly in school. This can look like symptoms of attention-deficit/hyperactivity disorder (ADHD).
• Loud snoring.
• Bedwetting.
• Frequent arm or leg movements while asleep.
• Sleeping in unusual positions or sleeping with their neck extended.
• Reflux (heartburn) or night sweats.

Causes of sleep apnea

Certain mechanical and structural problems in the airway cause the interruptions in breathing during sleep. Apnea happens:

• When the throat muscles and tongue relax during sleep and partially block the opening of the airway
• When the muscles of the soft palate at the base of the tongue and the uvula relax and sag, the airway becomes blocked, making breathing labored and noisy and even stopping it altogether
• In overweight people when an excess amount of tissue in the airway causes it to be narrowed
• With a narrowed airway, the person continues their efforts to breathe, but air can’t easily flow into or out of the nose or mouth
• In central sleep apnea, there is a brief lack of communication between the brain and the muscles that control breathing possibly due to underlying brain or heart conditions

Sleep apnea usually has specific causes, and there’s evidence that it may run in families. Overall, the three main types of sleep apnea, also has some differences in how and why they happen.

Obstructive sleep apnea (OSA)

Obstructive sleep apnea happens when muscles in your head and neck relax while you’re asleep, causing the surrounding tissue to press on your windpipe. That obstructs air’s ability to pass through it.

Central sleep apnea (CSA)

This form of sleep apnea happens because of a problem in your brain. Under ordinary circumstances, your brain manages your breathing all the time, including while you sleep. Central sleep apnea happens when your brain doesn’t send signals to keep breathing-related muscles working. Central sleep apnea can happen for many reasons, including:

• Heart failure.
• Low blood oxygen levels (hypoxia) because of high altitude.
• Nervous system damage, especially in your brainstem (which is what manages your breathing) or parts of your spinal cord.
• Treating obstructive sleep apnea initially with CPAP (this typically goes away with consistent CPAP use).
• Nervous system conditions like amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig’s disease).

Mixed/complex sleep apnea

There’s also a mixed/complex type of sleep apnea. This form has a combination of both obstructive events and central events. This happens when someone has OSA, diagnosed with a sleep study, that converts to CSA when receiving therapy for OSA

Symptoms and causes of paralysis

Risk factors of sleep apnea

Sleep apnea can affect anyone, even children. But certain factors increase your risk depending on the type you are having.

Factors that increase the risk of obstructive sleep apnea include:

• Excess weight. Obesity greatly increases the risk of OSA. Fat deposits around your upper airway can obstruct your breathing.
• Neck circumference. People with thicker necks might have narrower airways.
• A narrowed airway. You might have inherited a narrow throat. Tonsils or adenoids also can enlarge and block the airway, particularly in children.
• Being male. Men are 2 to 3 times more likely to have sleep apnea than are women. However, women increase their risk if they’re overweight or if they’ve gone through menopause.
• Being older. Sleep apnea occurs significantly more often in older adults.
• Family history. Having family members with sleep apnea might increase your risk.
• Use of alcohol, sedatives or tranquilizers. These substances relax the muscles in your throat, which can worsen obstructive sleep apnea.
• Smoking. Smokers are three times more likely to have obstructive sleep apnea than are people who’ve never smoked. Smoking can increase the amount of inflammation and fluid retention in the upper airway.
• Nasal congestion. If you have trouble breathing through your nose, whether from an anatomical problem or allergies, you’re more likely to develop obstructive sleep apnea.
• Medical conditions. Congestive heart failure, high blood pressure and type 2 diabetes are some of the conditions that may increase the risk of obstructive sleep apnea. Polycystic ovary syndrome, hormonal disorders, prior stroke and chronic lung diseases such as asthma also can increase risk.

Risk factors for central sleep apnea include:

• Being older. Middle-aged and older people have a higher risk of central sleep apnea.
• Being male. Central sleep apnea is more common in men than it is in women.
• Heart disorders. Having congestive heart failure increases the risk.
• Using narcotic pain medicines. Opioid medicines, especially long-acting ones such as methadone, increase the risk of central sleep apnea.
• Stroke. Having had a stroke increases the risk of central sleep apnea.

Complications of sleep apnea

Sleep apnea is a serious medical condition. Complications of obstructive sleep apnea include:

• Daytime fatigue. The repeated awakenings associated with sleep apnea make typical, restorative sleep impossible, in turn making severe daytime drowsiness, fatigue and irritability likely.You might have trouble concentrating and find yourself falling asleep at work, while watching TV or even when driving. People with sleep apnea have an increased risk of motor vehicle and workplace accidents.You might also feel quick-tempered, moody or depressed. Children and adolescents with sleep apnea might perform poorly in school or have behavior problems.
• High blood pressure or heart problems. Sudden drops in blood oxygen levels that occur during OSA increase blood pressure and strain the cardiovascular system. Having OSA increases your risk of high blood pressure, also known as hypertension. OSA might also increase your risk of recurrent heart attack, stroke and irregular heartbeats, such as atrial fibrillation. If you have heart disease, multiple episodes of low blood oxygen (hypoxia or hypoxemia) can lead to sudden death from an irregular heartbeat.
• Type 2 diabetes. Having sleep apnea increases your risk of developing insulin resistance and type 2 diabetes.
• Metabolic syndrome. This disorder, which includes high blood pressure, abnormal cholesterol levels, high blood sugar and an increased waist circumference, is linked to a higher risk of heart disease.
• Complications with medicines and surgery. Obstructive sleep apnea is also a concern with certain medicines and general anesthesia. People with sleep apnea might be more likely to have complications after major surgery because they’re prone to breathing problems, especially when sedated and lying on their backs.Before you have surgery, tell your doctor about your sleep apnea and how it’s being treated.
• Liver problems. People with sleep apnea are more likely to have irregular results on liver function tests, and their livers are more likely to show signs of scarring, known as nonalcoholic fatty liver disease.
• Sleep-deprived partners. Loud snoring can keep anyone who sleeps nearby from getting good rest. It’s common for a partner to have to go to another room, or even to another floor of the house, to be able to sleep.

Complications of Central sleep apnea include:

• Fatigue. The repeated awakening associated with sleep apnea makes typical, restorative sleep impossible. People with central sleep apnea often have severe fatigue, daytime drowsiness and irritability. You might have difficulty concentrating and find yourself falling asleep at work, while watching television or even while driving.
• Cardiovascular problems. Sudden drops in blood oxygen levels that occur during central sleep apnea can adversely affect heart health.If there’s underlying heart disease, these repeated multiple episodes of low blood oxygen, known as hypoxia or hypoxemia. This worsen prognosis and increase the risk of irregular heart rhythms.

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Prevention of sleep apnea

Sleep apnea is sometimes preventable, especially in cases where it happens because a person has excess weight or obesity. Still, some people maintain a healthy body weight or are underweight and still develop sleep apnea. For those individuals, a structural issue is usually the cause of their apnea, so they can’t prevent it.

The best things you can do to reduce your risk of sleep apnea include:

• Reach and maintain a healthy weight.
• Practice good sleep hygiene.
• Manage any existing health conditions, such as high cholesterol, high blood pressure and Type 2 diabetes.
• See your healthcare provider at least once a year for a checkup.

Diagnosis of sleep apnea

Your health care provider may make an evaluation based on your symptoms and a sleep history, which you can provide with help from someone who shares your bed or your household, if possible.

An evaluation often involves overnight monitoring of your breathing and other body functions during sleep testing at a sleep center. Home sleep testing also might be an option. 

A primary healthcare provider, pulmonologist, neurologist, or other healthcare provider with specialty training in sleep disorders may make a diagnosis and start treatment. Several tests are used to evaluate sleep apnea, including:

• Nocturnal polysomnography. During this test, you’re hooked up to equipment that monitors your heart, lung and brain activity, breathing patterns, arm and leg movements, and blood oxygen levels while you sleep.
• Home sleep tests. Your health care provider might provide you with simplified tests to be used at home to diagnose sleep apnea. These tests usually measure your heart rate, blood oxygen level, airflow and breathing patterns. Your provider is more likely to recommend polysomnography in a sleep testing facility, rather than a home sleep test, if central sleep apnea is suspected. If the results aren’t typical, your provider might be able to prescribe a therapy without further testing. Portable monitoring devices sometimes miss sleep apnea. So your health care provider might still recommend polysomnography even if your first results are within the standard range.

If you have obstructive sleep apnea, your health care provider might refer you to an ear, nose and throat specialist to rule out a blockage in your nose or throat. An evaluation by a heart specialist, known as a cardiologist, or a doctor who specializes in the nervous system, called a neurologist, might be necessary to look for causes of central sleep apnea.

Treatment of sleep apnea

There are many approaches to treating sleep apnea, depending on the specific type of sleep apnea and how severe it is. While none of these is a cure, they can help prevent apnea events or reduce how often they happen or how severe they are.

Many treatments should be a part of your daily (or nightly) routine. That can ultimately reduce or even eliminate sleep apnea’s effects on your life for as long as you use these treatments.

Possible treatments include:

• Conservative (nonmedical) treatments.
• Positive airway pressure and adaptive ventilation devices.
• Oral appliances (mouthpieces).
• Nerve stimulators.
• Surgery/medical procedures.
• Medications (central sleep apnea only).

Conservative treatments

These nonmedical treatments or approaches can typically improve obstructive sleep apnea or resolve it. They aren’t cures, but they can reduce apnea to the point where it stops happening or isn’t severe enough to cause symptoms. These include:

• Weight loss. A 10% decrease in body weight can significantly improve sleep apnea for people who have excess weight or obesity.
• Position changes while sleeping and sleep aid items. Sleeping on your back makes sleep apnea more likely to happen. Special support pillows and similar items can help change the position in which you sleep, keeping you off your back so soft tissue doesn’t press on your windpipe and block breathing.
• Nasal sprays, adhesive strips, etc. These over-the-counter products improve breathing by making it easier for air to travel through your nose. While they can’t help moderate or severe sleep apnea, they can sometimes help snoring and mild sleep apnea.
• Treating the underlying condition. Treating conditions such as heart failure can often improve central sleep apnea.
• Medication changes. Working with your doctor to decrease or stop opioid pain medications may be able to improve or even resolve central sleep apnea.

Positive airway pressure (PAP) and adaptive ventilation

Positive airway pressure is a method that uses a specialized device to increase the air pressure inside of your airway while you inhale. This method can treat obstructive, central and mixed sleep apneas.

Pushing pressurized air down your windpipe keeps it open so you can breathe. These devices push air through a hose that attaches to a special mask you wear on your face while you sleep. Masks can cover your nose, mouth or both, and there are many different types and styles to choose from.

The best-known PAP device is the Continuous Positive Airway Pressure (CPAP) machine. However, there are other types of PAP machines, too (see the CPAP Machine article for more about the different types of devices, including adaptive servo-ventilation devices). These devices increase the air pressure inside of your airway and lungs when you inhale, keeping surrounding tissue from pressing your airway shut.

Oral devices

Obstructive sleep apnea happens when soft tissue in your head or neck, especially around your mouth and jaw, press downward on your windpipe. Special mouthpiece devices can help hold your jaw and tongue in a position that keeps pressure off your windpipe. Dentists and sleep medicine specialists often work together to make these for people who need them.

Nerve stimulators

The hypoglossal nerve (the name comes from Greek and means “under the tongue”) is what controls your tongue’s movements. A nerve stimulator attached to this nerve can stimulate it, pushing your tongue slightly forward when you breathe while you’re sleeping. That keeps your tongue from relaxing and pressing backward on your windpipe while you sleep, which is one of the ways that obstructive sleep apnea happens.

An electrode attaches to the nerve under your jaw and connects to a device implanted under the skin in your chest. You can turn the stimulator on before you sleep and turn it off after you wake up. The electrical current is strong enough to keep your tongue from relaxing too much, but mild enough that it’s not uncomfortable.

A similar kind of nerve stimulation is also possible with central sleep apnea. This type of stimulation affects the phrenic nerves. This pair of nerves connect your spinal cord to the diaphragm, a layer of muscle underneath your lungs that controls your ability to inhale and exhale. Stimulating the phrenic nerve causes those muscles to flex, helping you breathe.

Surgery/Medical procedure

Surgeries on your nose, mouth and throat can help prevent blockages of your nose, throat and windpipe. However, the impact of these in adults is usually limited and varies from person to person. These surgeries include:

• Somnoplasty. This procedure uses radiofrequency (RF) to reduce soft tissue around the upper parts of your windpipe.
• Tonsillectomy/adenoidectomy. Removing your tonsils and adenoids can widen the opening where your mouth, throat and nasal passages connect. That makes it easier for air to pass through and reduces soft tissue that can block your breathing. This procedure is most helpful for children with obstructive sleep apnea.
• Uvulopalatopharyngoplasty (UPPP). This procedure removes your uvula (the teardrop-shaped soft tissue that hangs at the back of your mouth). It also removes soft tissue from your soft palate and pharynx. These widen the area where your mouth and throat meet, making it easier for air to pass through.
• Jaw surgery. Different surgery procedures can subtly change the position of your jaw so soft tissue can’t easily press back on your airway. These procedures are especially helpful for people who have sleep apnea for structural reasons like micrognathia.
• Nasal surgery. One common form of nasal surgery is septoplasty, which straightens the soft tissue in your nose, making it easier for air to travel through your nose and nasal passages.

Medications for central sleep apnea

In addition to positive airway pressure, adaptive ventilation and phrenic nerve stimulators, there are some medications that may help central sleep apnea. Some examples of these medications include hypnotic (sleep-promoting) medications, respiratory-stimulating drugs and more. However, none of these medications are formally approved or definitively accepted for this use.

People who have sleep apnea should avoid heavy drinking, and frequent use of sleeping pills or other drugs (recreational and otherwise) that cause heavy sedation. These can make sleep apnea worse. Your healthcare provider can talk to you about drugs that can cause that and how you can avoid the effects.

Diagnosis and treatment of COPD (chronic obstructive pulmonary disease)

The complications and side effects of the treatments depend on many factors, especially the treatments themselves. Your healthcare provider is the best source of information for what you can do to minimize the side effects or prevent them when possible.

The time it takes to recover or feel better after treatment for sleep apnea depends on the treatments themselves. Some people will feel better almost immediately, while others may need three to six months of consistent nightly treatment to see the full benefits. Your healthcare provider can tell you more about the timeline for your recovery and when you should expect to feel better.

Devices that treat sleep apnea, especially positive airway pressure devices, often bring very fast results. Older devices may take some tweaking and adjusting (a process known as “titration”) of the settings, but many newer devices can often adjust automatically to meet your needs (especially if your sleep apnea is mild or on the low end of moderate).

While some people may need to get used to wearing a mask to sleep, most people can overcome that fairly quickly. Many people see improvements immediately when they sleep through the night using a positive airway pressure device.

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