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An in-depth report on the causes, diagnosis, treatment, and prevention of sleep apnea.
Sleep apnea has a strong association with several diseases, particularly those related to the heart and circulation.
Researchers are intensively investigating why a problem in the upper airways is associated with serious conditions of the heart and circulatory system. Here are some of their findings:
At this time, however, evidence of a clear causal relationship with any of these health problems is still weak. Some studies have found no significant independent risk for heart disease from obstructive sleep apnea. The following are some discussions on the possible effects of apnea on specific health problems.
High Blood Pressure. A number of studies have found a strong association between sleep apnea and high blood pressure (hypertension). (In the past, the link between sleep apnea and hypertension was thought to be due to obesity, a risk factor for both conditions, but more recent studies contradict that theory.) A 2000 study followed patients for 4 years; the more nightly apnea episodes they had in the first year, the more likely they were to develop hypertension by the fourth year. A weak, but still higher-than-normal association with high blood pressure has also been observed in those who snore, wake frequently during the night, or have mild sleep apnea.
A 2004 data analysis of over 200,000 patient records revealed that people who took both antidepressants and antihypertensives were 18 times more likely to be diagnosed with obstructive sleep apnea than those who did not take the medications. The probability was highest among adults aged 20-39 years. These drugs do not cause sleep apnea, but antidepressants may be prescribed to treat hypertensive patients’ complaints of fatigue even if sleep apnea is the real cause. The researchers recommended that patients being treated for high blood pressure, depression, and fatigue should also be evaluated for sleep apnea.
One way that apnea may directly affect blood pressure, regardless of other risk factors:
Coronary Artery Disease and Heart Attack. Sleep apnea has been associated with heart disease regardless of the presence of high blood pressure or other heart risk factors. In a 2001 study, researchers observed that the more episodes of apnea and hypopnea a patient had, the higher the risk for a heart attack. Many of the factors associated with stroke and sleep apnea (a risk for blood clots and narrowing of the arteries) may also increase the risk for heart attacks. Obstructive sleep apnea, however, may have other effects that increase the risk for heart problems:
Stroke. Sleep apnea doubles the risk for stroke. The worse the sleep apnea, the greater the risk; moderate-to-severe obstructive sleep apnea can triple the risk of stroke. Sleep apnea is also associated with high blood pressure, a known risk factor for stroke. However, people who have sleep apnea, but not high blood pressure, are also still at increased risk for stroke. Sleep apnea in stroke patients is also associated with a higher risk for worse symptoms after a stroke, including delirium, depression, poor response to speech, and difficulty conducting daily chores.
Heart Failure. Studies suggest that 11 - 37% of patients with heart failure also have sleep apnea. Central sleep apnea is particularly linked with heart failure. The evidence for the association between heart failure and sleep apnea includes:
Atrial Fibrillation. Sleep apnea is more common in people with atrial fibrillation (irregular heartbeat) than in patients with other heart conditions. In a 2005 study published in Circulation , 49% of patients with atrial fibrillation were at risk for developing apnea, compared with 32% of general cardiology patients. An earlier study indicated that patients with untreated obstructive sleep apnea may be at increased risk for recurrence of atrial fibrillation. Patients with atrial fibrillation who received CPAP treatment had a lower risk for recurrence.
Metabolic Syndrome. The metabolic syndrome (also called Syndrome X) is a cluster of abnormalities that cause insulin resistance. Some of these factors, including hypertension and obesity, are also associated with sleep apnea. A 2004 study found that metabolic syndrome was nine times more common among patients with obstructive sleep apnea, independent of obesity.
When it comes to sleep apnea and obesity, it is not always clear which condition is responsible for the other. For example, obesity is often a risk factor and possibly a cause of sleep apnea, but it is also likely that sleep apnea increases the risk for weight gain. Some studies indicate that sleep apnea disrupts rapid eye movement (REM) sleep, which, in turn, increases the risk for obesity. Research indicates that animals deprived of REM sleep tend to eat more. People with apnea may also become too tired to exercise and so put on weight.
Sleep apnea is associated with a higher incidence of many medical conditions, other than heart and circulation. The links between apneas and the conditions are unclear.
Mental Issues in Adults . Some studies have reported that older people with sleep apnea and daytime sleepiness have lower scores on tests for mental functions, such learning and attention. One expert suggested that treating sleep apnea in older patients may correct some cases of dementia that are caused by sleep disturbances. Elderly people with sleep apnea may also be more prone to depression.
Emotional Effects of Sleep Apnea. Studies report an association between severe apnea and psychological problems. In one study, 32% of patients had symptoms of depression. Sleep-related breathing disorders can also worsen nightmares and post-traumatic stress disorder. In one study, treatment of sleep apnea eased these complaints. Certainly, daytime sleepiness interferes with quality of life. It is also possible that severe emotional problems might worsen the apnea.
Because sleep apnea so often includes noisy snoring, the condition can also adversely affect the sleep quality of a patient's bed partner. Spouses or partners may also suffer from sleeplessness and fatigue. In some cases, the snoring can disrupt relationships. Diagnosis and treatment of sleep apnea in the patient can help eliminate these problems.
Failure to Thrive. Small children with undiagnosed sleep apnea may "fail to thrive," that is, they do not gain weight or grow at a normal rate and they have low levels of growth hormone. In severe cases, this may affect the heart and central nervous system. Most often sleep apnea in children is caused by overgrown tonsils or adenoid. Their removal often completely solves all of these problems, including resolution of sleep apnea and restoring weight gain and normal growth hormone levels.
Attention Deficits and Hyperactivity. Problems in attention and hyperactivity are common in children with sleep apnea. There is some evidence that such children may be misdiagnosed with attention-deficit hyperactivity disorder. Snoring, rather than sleepiness, is a stronger risk factor for hyperactivity in many of these children, especially boys under 8 years old. (Even children who snore and do not have sleep apnea may be at higher risk for poor concentration.)
Some researchers believe that sleepiness associated with sleep apnea is the greatest risk factor for car accidents. As many as 200,000 automobile accidents in the U.S. and 1,500 deaths from such accidents are caused by sleepiness. Studies continue to report that drowsy driving is as risky as drunk driving. Several studies have suggested that people with sleep apnea have two to three times as many car accidents, and five to seven times the risk for multiple accidents.
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