It’s easy to take for granted that your body will keep working when you go to sleep: your heart should keep pumping blood to your arteries, your kidneys should keep filtering blood, and your lungs should continue to exchange oxygen and carbon dioxide in and out of your bloodstream as you breathe.
But what if that doesn’t happen?
Sleep apnea is one condition that challenges our basic ideas about the automatic function of our bodies. When we experience “apneas”, our body stops doing one basic thing that’s supposed to be automatic: taking in oxygen.
And by depriving the body of oxygen, sleep apnea can lead to a host of serious health conditions, and even death.
This article will examine a particular type of sleep apnea called positional sleep apnea.
The good news is that reducing - or outright eliminating - positional sleep apnea can be as simple as changing your sleeping position (we cover how to do that in our article on positional therapy for sleep apnea).
In this article, we explain the following in plain English:
What Is Sleep Apnea?
In order to understand positional sleep apnea, it’s helpful to first understand apnea more generally.
The word apnea comes from the Greek phrase for “no air”. Apnea is a temporary stoppage of breathing, defined by two features:
- 1It lasts 10 seconds or more
- 2It occurs with a drop in oxygen blood levels
Apnea can occur for a variety of reasons, including problems with the nervous system, blockages in the airway, or from medications, among other causes.
Sleep apnea is a stoppage of breathing during sleep, and it is by far the most common type of apnea. The related word hypopnea comes the Greek phrase meaning “insufficient air”, and refers to breathing that is too slow or too shallow to allow for normal oxygen delivery. It causes many symptoms, including daytime sleepiness, low energy, and a decrease in concentration.
The American Academy of Sleep Medicine, a group of physicians who specialize in treating sleep-related disorders, officially defines sleep apnea as having at least five apnea episodes per hour.
The more apnea episodes per hour, the more severe the apnea diagnosis.
The number of apnea episodes per hour is referred to by doctors as the apnea-hypopnea index, or AHI.
What Is Positional Sleep Apnea?
Positional sleep apnea occurs when you have more sleep apnea episodes while in certain sleeping positions, most notably while lying on your back versus your side.
Doctors use the apnea-hypopnea index to determine if a person has positional sleep apnea: if a sleep apnea patient can reduce their apnea episodes by half or more by changing sleeping positions, that individual has positional sleep apnea.
To define it in simpler terms: people with positional sleep apnea have at least twice as many apneas while lying on their back than on their side.
Two Types of Positional Sleep Apnea
Like all forms of sleep apnea, positional sleep apnea can be divided into two main types, based on the cause of the apnea.
Positional obstructive sleep apnea occurs when muscles of the upper airway (the air passages through the nose, mouth and throat) relax during sleep. The process goes like this:
Snoring indicates obstruction of air flow, but snoring doesn’t necessarily mean that a person has sleep apnea.
Both apnea and hypopnea result in a significant decrease in the amount of oxygen carried in the bloodstream, sometimes up to 40%.
This oxygen reduction is sensed by the brain’s surveillance system and trips the brain’s alarm, which alerts the body to wake up from sleep to resume normal breathing.
As an individual resumes sleeping, this pattern repeats, sometimes hundreds of times over the course of sleep. The end result is that sleep gets too fragmented and doesn’t achieve a deep enough stage to provide the necessary restoration that it’s supposed to.
Positional central sleep apnea also means that a person’s breaths start and stop abnormally during sleep, and to some degree can also be made worse or better by sleeping position.
However, positional central sleep apnea has a different cause: the brain’s defective communication with the muscles that help control breathing.
Positional central sleep apnea is not as common as positional obstructive sleep apnea, but it can be more dangerous.
In positional central sleep apnea, the brain also senses the lower levels of blood oxygen, and attempts to wake the body up to resume normal breathing. That creates the same pattern as in obstructive sleep apnea. However, when the brain, the breathing muscles, or the nerve connections between them are compromised, the brain may not be able to accomplish this task very easily.
How Does Sleeping Position Affect Sleep Apnea?
The position we sleep in can have a big impact on both central and obstructive sleep apnea.
Sleep specialists recognize three primary sleeping positions:
These distinctions are important because of the effects of gravity on muscles and other tissues of the airway while in each position.
The greater the force of gravity on these tissues, the greater the chance that the upper airway will collapse and obstruct air flow.
All of these tissues, and the muscles that control them, are under the influence of gravity, and the pull of gravity can be increased or decreased with changes in sleeping position.
The supine sleeping position (sleeping on your back) is considered the position in which obstructive sleep apnea symptoms are most likely to be experienced. It works like this:
When a person shifts to a lateral sleeping position (sleeping on your side), the effects of gravity decrease. Thus, in the side-sleeper position, sleep apnea symptoms are less likely (though snoring may still occur).
In the prone sleeping position (face-down), the forces of gravity on the upper airway tissues are the smallest. Recent studies have shown that face-down sleepers are the least likely to experience obstructive sleep apnea symptoms, and researchers are increasingly recommending prone sleeping to reduce those symptoms.
What Are the Causes of Positional Sleep Apnea?
In this article we’ve explained that sleeping supine (on your back) is the primary cause of positional sleep apnea, because sleeping on your back causes gravity to collapse your upper airway, thereby cutting off the flow of air into your body.
So understanding how the upper airway works, and how your upper airway is responding to back-sleeping, is key to figuring out the best solution for your positional sleep apnea.
To understand how the upper airway works, we need to explain the bones, soft tissues, and muscles that make up that area of the body:
Bones of the Upper Airway
Fractures, displacement or abnormal development of any of these bones can result in an interruption of air flow, and eventually to obstructive sleep apnea symptoms.
Soft Tissues of the Upper Airway
Muscles of the Upper Airway
The entire airway is lined with muscles that allow it to contract and expand.
If these muscles are damaged, inactivated, or impacted by gravity, they can also cause the obstruction that leads to sleep apnea by reducing the amount of air volume that the lungs receive.
So to summarize, there are many components of your upper airway’s bone structure, soft tissues, and muscles that can cause positional sleep apnea.
But no matter what the cause is, sleep apnea can often be improved by changing the body’s position while sleeping. We cover how below, but first, let’s quickly cover the type of person who typically suffers from positional sleep apnea.
Who Gets Positional Sleep Apnea? Profile of a Typical Patient
When you imagine who gets sleep apnea, you might think of someone who is morbidly obese, male, older, snores often and gets awakened dozens of times per night.
It is certainly true that someone with these characteristics is at risk for sleep apnea.
- Less obese
And have less severe sleep apnea (i.e. mild or moderate) than a typical sufferer of obstructive sleep apnea.
There is also some evidence that Asians are more inclined to have positional sleep apnea (and those that do are also less obese, like non-Asian patients with positional sleep apnea).
Many patients who have positional sleep apnea are able to reduce their apnea symptoms, or even cure the condition altogether, by changing sleep positions from the supine (back-sleeping) position to lateral (side-sleeping) or prone (face-down) positions.
If you have sleep apnea, the milder your condition is, the greater the chance you have positional sleep apnea. According to studies, nearly 50% of people with mild sleep apnea symptoms had positional sleep apnea, compared with about 20% in those with moderate symptoms. Those with more severe symptoms had positional sleep apnea only 6.5% of the time.
How to Know If You Have Positional Sleep Apnea
There are several methods to help you determine if your sleep apnea is primarily caused by your sleeping position. They are listed here from the most accurate (but requiring the most commitment to complete) to the least accurate (but requiring the least amount of work).
Sleep study: Also called “polysomnography” by sleep specialists, a sleep study typically takes place in a hospital or medical center, where you would sleep overnight in a specially-equipped room. The study measures your brain activity, eye movements, breathing patterns and cardiac activity while you sleep. This information can be coordinated to identify the primary causes of sleep disorders.
At-home sleep study: This test is a much more simplified and less expensive version of the sleep study that uses a small monitor to track respiratory patterns, oxygen levels and heart rate.
Online sleep apnea quizzes: Many commercial and academic websites offer quizzes which can help you assess whether or not you have positional sleep apnea. The sleep specialist doctors at AASM have an online quiz to assess your risk for sleep apnea, and the advocacy group at the American Sleep Apnea Association provides links to questionnaires used by sleep medicine specialists in their offices.
Self-assessment: If you are not obese and have mild symptoms, the chance that you have positional sleep apnea is much higher. You can use the online sleep apnea quiz above to establish a baseline understanding of your symptoms, such as snoring, frequently waking up from sleep, gasping for air upon awakening, stopping breathing when resuming sleep. You can assess if changing position seems to reduce those symptoms.
Observations from your bed partner: If you share a bed with someone, you can ask your partner about whether or not you experience the symptoms of sleep apnea. You can also ask your partner if these symptoms improve when you are in the lateral or prone positions versus lying supine.
Even the less accurate methods listed here are convenient, easy to do and may help you get started on your pursuit of treatment. They can help you learn more about positional sleep apnea as you talk with your physician about improving your symptoms.
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