Sleep apnea is characterized by repeated episodes of breathing cessation (apnea) during sleep. These episodes last from 10 seconds to nearly a minute, ending with a brief partial arousal.
This can occur (and disrupt sleep) hundreds of times throughout one night. An estimated 12 million Americans have obstructive sleep apnea, yet 95 percent of them are undiagnosed and untreated.
Sleep apnea causes
In some people, sleep apnea is the result of a central nervous system abnormality that interferes with the normal instinct to breathe. In others, it results from a collapse and blockage of the upper airway during sleep, due to anatomical factors that narrow the upper airway (such as large tonsils), excess fat in the tissues around the throat, or an enlarged tongue.
A large neck (collar size more than 17 inches in men or 16 inches in women) is also strongly linked to sleep apnea. Some people have both the anatomical and the nervous system causes at the same time.
Obesity, older age, weakness of the airway muscles, smoking, and hypothyroidism are additional risk factors.
Consuming alcohol or sedatives before going to sleep can further reduce the activity of the airway muscles.
Sleep apnea symptoms
The most pervasive and troublesome symptom of sleep apnea is excessive daytime sleepiness caused by poor sleep at night. People with sleep apnea may fall asleep during the day while reading or even while driving, so there is a major risk of motor vehicle accidents.
They may also suffer from memory loss and personality changes. Although loud snoring is a common sign of sleep apnea, snoring itself does not indicate obstructive sleep apnea.
More than half of individuals with sleep apnea also have high blood pressure, and their blood pressure does not fall during sleep as it does in most people. In fact, sleep apnea has been shown to be an independent, treatable cause of high blood pressure. Research suggests that sleep apnea also doubles the risk of stroke in some people.
Heart rate tends to slow dramatically during periods of apnea and then rise rapidly when breathing resumes. Some evidence suggests that periods of apnea and the resulting low levels of oxygen in the blood, along with persistently high blood pressure, increase the risk of coronary heart disease and blood glucose intolerance. Researchers are currently studying these links.