Types of Sleep Apnea

There are three types of sleep apnea:

1. Obstructive sleep apnea (OSA)
2. Central sleep apnea (CSA)
3. Complex or mixed (also called treatment-emergent central sleep apnea)

As explained in my article What is Sleep Apnea, the common and potentially lethal aspect of this condition is the fact that sleep is repeatedly disrupted due to impaired breathing. The underlying cause of the impaired breathing — physical vs. neurological — is the distinguishing factor when it comes to type.

Obstructive sleep apnea (OSA)

Obstructive sleep apnea, sometimes called obstructive sleep apnea syndrome (OSAS) or obstructive sleep apnea-hypopnea syndrome (OSAHS), occurs when the sleeper fully relaxes resulting in a completely or partially blocked airway.

The specific cause of a blockage can vary ranging from the tongue falling back blocking the opening in the throat (i.e., when the sleeper is supine, for example) to interference from the uvula or tonsils to a fully or partially collapsed airway. Collapsed airways during sleep can occur due to excess tissue from body fat, reduced muscle tone from aging, genetics (family history) or the use of certain medications.

The estimated world wide prevalence of obstructive sleep apnea in adults is in the range of 1 billion people. That’s roughly 1 in 5 adults.

Obstructive sleep apnea is, by far, the most common form of sleep apnea. According to Medscape, in the general population, the prevalence of central sleep apnea is less than 1%.

Central sleep apnea (CSA)

Central sleep apnea is a condition in which the brain fails to signal the respiratory muscles to breathe during sleep. It can be more of a challenge to treat than OSA because there is no physical blockage affecting the airway. With central sleep apnea there is an absence of respiratory effort associated with each apnea or hypopnea.

So, while many of the symptoms and health effects of central sleep apnea are the same as those associated with obstructive sleep apnea, the underlying causes are quite different. Central sleep apnea may involve conditions such as Parkinson’s, ALS (amyotrophic lateral sclerosis often called Lou Gehrig’s disease), Alzheimer’s, heart failure and stroke to name a few. In some cases, medications (e.g., opioids) can cause cessations from breathing effort. In other cases there is no discernible cause.

The essential difference between OSA and CSA is obstructive sleep apnea is a physical problem while central sleep apnea is mental or neurological in nature.  

Complex sleep apnea syndrome (compSAS)

Complex sleep apnea (or mixed sleep apnea) includes elements of both obstructive sleep apnea and central sleep apnea. According to mayoclinic.org, some people with obstructive sleep apnea develop central sleep apnea while being treated with continuous positive airway pressure (CPAP). This condition is known as treatment-emergent central sleep apnea.  

For most people, treatment-emergent central sleep apnea goes away with continued use of a CPAP therapy. Other people may be treated with a different kind of positive airway pressure therapy.

According to a 2016 article authored by Robert Thomas, M.D. at myapnea.org, Medicare’s criteria for diagnosing complex sleep apnea calls for

• 5 or more central apneas per hour of sleep
• central apneas make up more than 50% of all breathing events
• obstructive events are less than 5 per hour of sleep  

A 2013 study on complex sleep apnea syndrome published at the National Institutes of Health website concluded that CSA events during initial CPAP titration are transient and disappear after continued CPAP use. This study also acknowledged that the definition of complex sleep apnea is diverse in the literature.

In summary, there are three types of sleep apnea with obstructive sleep apnea being the most common – by far. Obstructive sleep apnea is the result of a physical blockage in one’s airway during sleep while the root cause of central sleep apnea stems from the brain. Complex sleep apnea is a combination of both.

Other terms that often come up when discussing the types of sleep apnea are hypopnea, RERA and UARS. These are discussed at length in the post Apnea vs. Hypopnea vs. RERA.