What Causes Sleep Apnea? Everything You Should Know

Sleep apnea is a common condition in the United States, affecting an estimated 2-9% of adults¹, but many cases are believed to go undiagnosed.

If left untreated, sleep apnea can cause lower-quality sleep, loud snoring, or daytime tiredness. It can also affect the body's supply of oxygen, leading to potentially serious health problems² such as:

  • High blood pressure

  • Stroke

  • Heart attack

  • Diabetes

  • Heart failure

  • Cardiomyopathy (enlargement of the heart muscle tissue).

Untreated sleep apnea can also be responsible for car accidents, lost productivity at work, and work-related accidents, as well as underachievement in school in children and adolescents.

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What is sleep apnea?

Sleep apnea is a sleep disorder in which your breathing is repeatedly interrupted during sleep. Sleep apnea happens when the upper airway muscles relax during sleep and pinch off the airway, preventing you from getting enough air.

These breathing pauses can last for 10-20 seconds and can happen about five times an hour to as many as 100 or more times an hour, for up to a minute at a time.

During a sleep apnea episode, the lack of oxygen causes you to rouse slightly, open your upper airway, possibly snort and gasp, and then drift back to sleep almost immediately. In most cases, you won't even realize you are waking up.

These micro awakenings disrupt your sleep pattern and prevent the deepest, most restful sleep. This results in a much lower quality of sleep, leaving you feeling tired the next day, despite seemingly having had a full night's sleep.

There are three main types of sleep apnea:

  • Obstructive sleep apnea: This is the most common type of sleep apnea. Obstructive sleep apnea happens when air can't flow into or out of the nose or mouth, although you're trying to breathe. Breathing usually resumes with a loud gasp or body jerk. 

  • Central sleep apnea: The airway isn't blocked in central sleep apnea, but the brain fails to send the right signals to your muscles to make you start breathing. This type of sleep apnea is less common. 

  • Complex sleep apnea: Occurs when someone has both obstructive sleep apnea and central sleep apnea.

All three types of sleep apnea share certain common symptoms. Often, you won't notice the first signs of sleep apnea since they happen during sleep. Your bed partner will most likely notice that your breathing pauses, or they may complain about your loud snoring.

Symptoms of sleep apnea include:

  • Frequent, loud snoring

  • Gasping, choking, or snorting during sleep

  • Episodes in which you stop breathing during sleep 

  • Daytime sleepiness, no matter how much time you sleep

  • Restlessness during sleep

  • Sore throat or dry mouth after waking up

  • Mood disturbances such as anxiety or depression

  • Morning headaches.

What causes sleep apnea?

 Various factors can cause sleep apnea, including:


This is a common cause of sleep apnea in adults. Fat deposits in the neck and around the tongue and palate make the airway much tighter and smaller. It becomes much more constricted during sleep when lying down.

Note that non-obese people can also have obstructive sleep apnea and that not all overweight individuals have the condition.

Large tonsils

Large tonsils are the most common cause of obstructive sleep apnea in children because they narrow the upper airway. 

Endocrine disorders

The endocrine system produces hormones that can affect sleep-related breathing. Endocrine disorders like hypothyroidism (underactive thyroid), polycystic ovary syndrome (PCOS), and acromegaly (excess growth hormone) can cause tissue swelling near the airway. They are also associated with obesity, which causes sleep apnea. 

Heart failure

Sleep apnea is commonly found in people with heart failure³. That's because most patients with heart failure may have fluid buildup in their neck, which can obstruct the upper airway, causing sleep apnea. 

Anatomical characteristics

The size and positioning of a person's neck, jaw, tongue, tonsils, and other tissues near the back of the throat can directly affect airflow.

Physical attributes that can contribute to sleep apnea include a small upper airway, a small or receding jaw, a long soft palate, a high tongue position, and a deviated septum.

Genetic syndromes

Genetic syndromes that affect the skull or facial structure, especially those that cause the tongue to sit farther in the mouth, may cause sleep apnea. These include congenital central hypoventilation syndrome, cleft lip and cleft palate, and down syndrome. 

Neuromuscular conditions

Conditions that interfere with brain signals to chest and airway muscles can also cause sleep apnea. Such conditions include stroke, Lamber-Eaton myasthenic syndrome, and amyotrophic lateral sclerosis. 

Premature birth

Babies born prematurely (before 37 weeks of pregnancy) have a much higher risk for breathing problems during sleep. However, the risk decreases as the brain matures. 

What are the risk factors for developing sleep apnea?

While anyone can develop obstructive sleep apnea, certain factors can increase your risk of this condition.

Gender and age

While sleep apnea can occur at any age, the risk increases as you get older.

Age-related changes in how the brain controls breathing during sleep partly explain this, but another possible reason is that as we age, fatty tissue increases in the neck and around the neck.

Sleep apnea is more common in men than in women in younger adults, but the differences decrease with old age. 

Genetics and family history

If obstructive sleep apnea runs in your family, you may be at increased risk of having the condition.

How your airway is shaped and your cranial facial characteristics can be inherited from your family, which can all play a role in developing sleep apnea. 

Unhealthy lifestyle habits

Smoking, drinking alcohol, unhealthy eating habits, and lack of physical activity can increase your risk of developing sleep apnea.

  • Smoking can cause inflammation in the upper airway and how the brain controls sleep or muscles involved in breathing.

  • Drinking alcohol can cause tissue in the throat to relax, making it easier for the airway to become obstructed.

  • Unhealthy eating habits and a sedentary lifestyle increase your risk of obesity, resulting in sleep apnea.

Sleeping on your back

This sleeping position makes it easier for tissues around the airways to collapse and cause blockages.

How is sleep apnea diagnosed?

Proper diagnosis of sleep apnea requires a visit to a doctor if you're exhibiting symptoms. Your doctor will rule out any other possible reasons for your symptoms before diagnosing you with sleep apnea.

A diagnosis of sleep apnea begins with a complete medical history and physical examination. Your doctor will consider your signs and symptoms, whether you have a family history of sleep apnea, present risk factors, and whether you have complications of undiagnosed or untreated sleep apnea.

Your doctor will also perform a physical exam to identify any physical factors associated with sleep apnea, such as narrowing of the airway, obesity, large tonsils, or a large neck circumference.

They may also look at your jaw structure and size and tongue size and position, and check your neurological system, lungs, and heart to determine if you have any common sleep apnea complications.

To rule out other medical reasons or conditions, your doctor may conduct blood tests to check certain hormone levels and rule out endocrine disorders that could contribute to sleep apnea. They may also perform a pelvic ultrasound to rule out PCOS.

If your doctor determines that you have symptoms suggestive of sleep apnea, they may conduct a sleep study.

The only way to truly determine if someone has sleep apnea is to conduct a sleep study, typically performed overnight during regular sleeping hours, either in the sleep clinic or at home.

Sleep studies can detect apnea events (times when your breathing slows or stops during sleep), monitor your blood oxygen levels during sleep, detect low or high muscle activity levels that control breathing, and monitor heart and brain activity during sleep. It can also determine which type of sleep apnea you have.

The most common sleep studies used to diagnose sleep apnea include:

Polysomnogram (PSG)

This sleep study is performed in a sleep lab under the supervision of a trained technologist. PSG records various body functions during sleep, such as brain electrical activity, eye movement, muscle activity, heart rate, respiratory effort, airflow, and blood oxygen levels.

After the study, the number of times breathing is impaired during sleep is tallied, and the severity of sleep apnea is graded. 

Home sleep apnea test

This is typically for adults and is performed in the comfort of your home. The home sleep apnea test measures heart rate, blood oxygen levels, airflow, snoring, and breathing patterns.

Based on your home sleep test results, your doctor may still recommend a full in-hospital sleep study or recommend you start sleep apnea treatment.

Preventing sleep apnea

 The following can help you reduce the risks associated with sleep apnea:

  • Eat a healthy diet and exercise regularly: Healthy eating and staying active can help you maintain your weight and improve your overall health, reducing your risk of developing sleep apnea. 

  • Avoid sleeping on your back: Try sleeping on your side to reduce the risk of your tongue and soft palate collapsing into your airway, causing blockage and sleep apnea.  

  • Limit alcohol intake: Don't drink too much alcohol, especially shortly before going to sleep, and avoid sedatives, as they relax your muscles and suppress your central nervous signals. 

  • Stop smoking: Apart from increasing your risk of sleep apnea, smoking also puts you at risk of other health problems and illnesses such as cardiovascular disease and cancer.

The lowdown

Sleep apnea is a breathing disorder that causes intermittent disruptions of breathing during sleep.

It can be caused by obesity, large tonsils, endocrine disorders, neuromuscular disorders, heart failure, certain genetic syndromes, and premature birth.

Factors that can increase your risk of developing sleep apnea include age, unhealthy lifestyle habits, genetics, and family history.

Making lifestyle changes such as healthy eating and exercise can help reduce your risk of sleep apnea.

  1. Sleep Apnea | Sleep Foundation

  2. Sleep Apnea | NIH: National Heart, Lung, and Blood Institute

  3. Sleep apnea and heart failure | Science Direct

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