What Causes Sleep Apnea?
Medically reviewed by Valerie Cacho, MD
Obstructive sleep apnea is a condition that causes your airway to collapse or narrow while you sleep. As a result, oxygen can’t enter your body, and your oxygen levels may drop. This may damage your heart, lungs, and overall health.
Researchers have found four main causes of sleep apnea, including a narrow upper airway and problems controlling the muscles that keep the airway open during sleep. These causes can be interrelated, meaning more than one cause can lead to the onset of your sleep apnea symptoms.
Knowing the cause (or, what researchers call your sleep apnea “phenotype”) can help determine which treatments are most effective for your symptoms.
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Narrow or Collapsible Airway
The primary cause of sleep apnea is a narrow or collapsible airway. Think of this as trying to drink from a straw that is partially or completely blocked. While there are other causes of sleep apnea that aren’t related to how your airway looks, these causes usually occur in combination with a narrow airway.
Several factors can contribute to a narrowed or collapsible airway. These include:
Increased fat deposits in the neck, which pushes on the airway from the outside, causing it to become narrow
An enlarged tongue, which can fall back and prevent air from easily entering or escaping your mouth
More abdominal fat, which can put more pressure on the upper airway, making it easier for it to collapse
Smaller facial structures, like a small jaw
Longer length of the upper airways, which can block the airways in tall people or those with longer necks
Impairment in Muscle Control
A group of muscles called pharyngeal dilator muscles are located in your airways. These muscles help keep your airways open.
Sometimes, a dysfunction in the way these muscles work can lead to the onset of sleep apnea symptoms. Examples of disruption in these muscles include a change in how your brain controls these muscles, how well the muscles respond to messages from your brain, and if these muscles become weak over time.
Low Respiratory Arousal Threshold
Some people with sleep apnea have a low respiratory arousal threshold. This means you wake up more easily than other people do. People may even call you a “light sleeper” because of this ability.
When you have sleep apnea, you might wake up multiple times at night. Waking up frequently throughout the night or having interrupted rest leaves you feeling tired, groggy, or unrefreshed the next day.
Having a low respiratory arousal threshold can contribute to a change in your breathing and how often you wake up, further increasing your risk of developing sleep apnea.
Related: How Can You Tell If You Have Sleep Deprivation—And Why Is It Bad?
Respiratory Control Instability
Thanks to how your body and brain work, you don’t have to think about when and why to breathe. Your brain detects it for you by sensing the levels of carbon dioxide (CO2) in your body. When your CO2 becomes too high, your brain signals your body to breathe faster and deeper.
Some people have a different CO2 threshold than others—meaning that each person’s tolerance for CO2 can be different. Researchers call this phenomenon a “loop gain.” Having an increased loop gain can mean your body doesn’t respond to higher CO2 levels as fast as other people’s bodies do. As a result, you may be more likely to have periods where you stop breathing throughout the night, which may raise your risk of sleep apnea.
Is Sleep Apnea Hereditary?
Sleep apnea can be hereditary in two ways. First, your parents have certain genes that increase the risk of having sleep apnea, you might also inherit those genes. Secondly, sleep apnea can be hereditary if you inherit genetic qualities that are risk factors for developing sleep apnea. These genetic factors can include:
How much body fat you have
How your body fat is distributed throughout your body
What your face and skull structure look like
How your body controls your airway muscles
How well you sleep
Because sleep apnea is often underdiagnosed and genetic testing for it is still being studied, it’s hard to know to what exact extent sleep apnea is hereditary. However, researchers do know that having a biological parent with sleep apnea increases the risk of snoring or having periods where your breathing stops while you sleep.
Who Gets Sleep Apnea?
Some people are more likely to develop sleep apnea than others. Factors that can contribute to sleep apnea risk include:
Assigned sex at birth: People who were assigned male at birth have an increased risk of developing sleep apnea
Increasing age: Your risks for sleep apnea increase as you get older
Post-menopausal: Those assigned female at birth may experience greater rates of sleep apnea after going through menopause
Increased amount of body fat: Having a higher percentage of body fat can result in anatomy changes that lead to sleep apnea
Related: 4 Devices That Can Improve Sleep Apnea
Risk Factors
Healthcare providers consider obesity as a major risk factor for sleep apnea. About 50% of people with obesity have sleep apnea.
Other risk factors for sleep apnea include:
Age greater than 35
Body mass index (BMI) of 25 or higher
Excessive alcohol intake
Body Mass Index (BMI)
Body Mass Index, or BMI, is a biased and outdated metric that uses your weight and height to make assumptions about body fat, and by extension, your health. This metric is flawed in many ways and does not factor in your body composition, ethnicity, sex, race, and age. Despite its flaws, the medical community still uses BMI because it’s an inexpensive and quick way to analyze health data.
Having other medical conditions may also increase your risk of developing sleep apnea. These conditions include:
Hyperlipidemia (high cholesterol)
Hypertension (high blood pressure)
Managing these health conditions may help to prevent the likelihood of developing sleep apnea or reduce your symptoms if you already have a sleep apnea diagnosis.
A Quick Review
Sleep apnea is a condition that stops and restarts your breathing several times a night—leading to daytime sleepiness, headaches, and heart problems. The primary cause of sleep apnea is having a narrow or collapsible airway.
Certain risk factors, such as having other underlying medical conditions, being male, being over the age of 35, and drinking alcohol, may also increase your risk of developing sleep apnea.
If you or a loved one notices that you have symptoms of sleep apnea or experience interrupted sleep at night, it’s a good idea to get tested. Your healthcare provider can begin the diagnostic process and help you start treatment if necessary.
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