What is Obstructive Sleep Apnea?

As the first clinical post for this new blog, I thought I would start with the basics: what is “Obstructive Sleep Apnea” (OSA)? The answer is simple, but it’s also complicated.

In brief, OSA is a common medical condition (one study found that as many as 24% of adult men and 9% of adult women have it) that occurs during sleep where there are recurrent disruptions in sleep due to partial (“hypopnea”) or complete (“apnea”) obstructions of the upper airway.

The number of these events per hour of sleep is called “the Apnea-Hypopnea Index,” or “AHI.” The American Academy of Sleep Medicine (AASM) defines the cutoff for OSA in adults as an AHI of at least 5. It doesn’t matter if these are apneas or hypopneas – they are both counted the same. These terms are easier to understand and remember when they are broken down. The suffix “-pnea” is Greek for “breath.” The “a-” prefix means “absence of,” while the “hypo-” prefix means “small.”

MRI of an open airway.

MRI of an obstructed airway.

However, there is a relatively milder form of OSA known as “The Upper Airway Resistance Syndrome” (UARS). UARS is defined by milder breathing abnormalities during sleep that do not cause a partial or complete closure in the airway during sleep because the brain is continuously disrupted out of sleep to maintain the airway. These disruptions occur because the body has to work harder to generate a full breath against a very narrow airway. These frequent disruptions make sleep very inefficient, leading to symptoms.

In both OSA and UARS, there are many varying signs and symptoms. These can include some (or all) of the following: daytime sleepiness, snoring, frequent awakenings during the night, choking or gasping during sleep, teeth clenching or grinding, getting up to urinate frequently during the night (“nocturia”), sweating during the night, racing heart beat, nasal congestion that develops as the night goes on, heartburn/acid reflux (“GERD”), parasomnias (sleepwalking, sleep talking, etc.), and even insomnia.

As demonstrated by the Sleep Heart Health Study, moderate and severe OSA can increase the risk of cardiovascular disease, including stroke, heart attack, high blood pressure, and arrhythmias (e.g. atrial fibrillation).

There will be more posts under the “OSA” tag that will discuss how all of these symptoms can be attributed potentially to OSA, so check back frequently for updates.

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