Obstructive Sleep Apnea (OSA)

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Overview

Sleep apnea, also called obstructive sleep apnea (OSA), is a common disorder that affects more than 18 million people in the United States. In many of these people, the condition is undiagnosed. OSA takes its name from the Greek word apnea, which means "without breath." People with sleep apnea literally stop breathing repeatedly during their sleep, often for a minute or longer and as many as hundreds of times during a single night.

Sleep apnea can be caused by either complete obstruction of the airway (obstructive apnea) or partial obstruction (obstructive hypopnea—hypopnea is slow, shallow breathing), both of which can wake one up. There are three types of sleep apnea—obstructive, central, and mixed. Of these, obstructive sleep apnea (OSA) is the most common. OSA occurs in approximately 2 percent of women and 4 percent of men over the age of 35.

Causes

The exact cause of OSA remains unclear. The site of obstruction in most patients is the soft palate, extending to the region at the base of the tongue. There are no rigid structures, such as cartilage or bone, in this area to hold the airway open. During the day, muscles in the region keep the passage wide open. But as a person with OSA falls asleep, these muscles relax to a point where the airway collapses and becomes obstructed.

When the airway closes, breathing stops, and the sleeper awakens to open the airway. The arousal from sleep usually lasts only a few seconds, but brief arousals disrupt continuous sleep and prevent the person from reaching the deep stages of slumber, such as rapid eye movement (REM) sleep, which the body needs in order to rest and replenish its strength. Once normal breathing is restored, the person falls asleep only to repeat the cycle throughout the night.

Typically, the frequency of waking episodes is somewhere between 10 and 60. A person with severe OSA may have more than 100 waking episodes in a single night.

Risk Factors

The primary risk factor for OSA is excessive weight gain. The accumulation of fat on the sides of the upper airway causes it to become narrow and predisposed to closure when the muscles relax.

Age is another prominent risk factor. Loss of muscle mass is a common consequence of the aging process. If muscle mass decreases in the airway, it may be replaced with fat, leaving the airway narrow and soft. Men have a greater risk for OSA. Male hormones can cause structural changes in the upper airway.

Other predisposing factors associated with OSA include:

• Anatomic abnormalities, such as a receding chin
• Enlarged tonsils and adenoids, the main causes of OSA in children
• Family history of OSA, although no genetic inheritance pattern has been proven
• Use of alcohol and sedative drugs, which relax the musculature in the surrounding upper airway
• Smoking, which can cause inflammation, swelling, and narrowing of the upper airway
• Hypothyroidism, acromegaly, amyloidosis, vocal cord paralysis, post-polio syndrome, neuromuscular disorders, Marfan's syndrome, and Down syndrome
• Nasal congestion

Studies have shown that the risk for obstructive sleep apnea is higher in patients who have recently experienced a heart attack. Some physicians recommend OSA screening in heart attack patients.

Obstructive Sleep Apnea (OSA), Overview, Causes, Risk Factors reprinted with permission from sleepdisorderchannel.com
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