There are two kinds of sleep apnea. The most common, obstructive sleep apnea, occurs when the tongue and soft palette relax against the back of the throat, blocking the airway. The collapse in the throat causes pauses in breathing, sometimes occurring dozens of times per hour, and often lasting 30 to 45 seconds per interruption.
When a blocked airway prevents oxygen from entering the body, blood vessels constrict and blood pressure rises as much as 25 percent to 30 percent, doctors say. The activation of the sympathetic nervous system to make people wake up also increases the heart rate and blood pressure. What’s more, sleep apnea causes hormone levels to change in a way that reduces the effectiveness of insulin, leading to higher blood sugar and potentially diabetes.
Most people who have sleep apnea are unaware of these nighttime disruptions. Loud snoring and extreme daytime drowsiness are the usual symptoms of untreated obstructive sleep apnea.
The other type of sleep apnea, central sleep apnea, is a less common disorder. It results from weak signals from the brain to the diaphragm that draws air into the lungs when it contracts. It can be caused by congestive heart failure, stroke, brain damage, drugs and other problems.
The incidence of sleep apnea rises with age and can occur in men, women and children, but is more common in men. One out of 25 middle-aged men and one out of 50 middle-aged women have sleep apnea, but after menopause the prevalence in women rises steeply. It’s estimated that 3 percent of children have the sleep disorder.
Sleep apnea is more common in African Americans, Hispanics and Pacific Islanders than in Caucasians. And, if someone in your family has sleep apnea, you’re more likely to develop it than someone without a family history of the condition.
To diagnose sleep apnea, people are usually asked to stay overnight at a hospital sleep center to be studied. During that time, heart rate, oxygen saturation, brain waves, arousals and breathing movements are measured.