It’s well established that sleep apnea—characterized by repeated episodes of breathing cessation and partial awakening during sleep—contributes to daytime fatigue. Now, experts are beginning to realize that sleep apnea can have more serious consequences as well.
Fortunately, treatment for sleep apnea (including lifestyle measures, weight loss, and continuous positive airway pressure [CPAP]) can help resolve the sleep apnea as well as some of these related health problems.
Motor Vehicle Accidents and Sleep Apnea
Research has shown that people with sleep apnea are up to nine times more likely to have an accident while driving than people without sleep apnea. The daytime drowsiness that accompanies sleep apnea impairs driving skills, similar to someone who has a blood alcohol level over the legal limit.
But CPAP therapy for sleep apnea—which involves wearing a nasal mask that delivers a steady stream of air to maintain air pressure and keep airways open—can have a quick and dramatic effect on driving ability, according to a 2004 study.
Researchers used a driving simulator to test the skills and reflexes of 36 people with sleep apnea (18 who were just beginning CPAP and a control group of 18 who were not being treated). Participants performed the 20-minute driving test 1, 3, and 7 days into a two-week CPAP trial period; then CPAP was discontinued and all participants performed the test 1, 3, and 7 days later.
Within seven days after beginning CPAP, participants improved their reaction time and ability to keep the simulated car on the road. The control group’s scores did not improve, suggesting that the CPAP group’s improvements were not due to growing familiarity with the simulator. After discontinuing CPAP, participants’ scores remained stable during days 1 and 3 but began to worsen by day 7. This finding suggests that CPAP improves driving ability rapidly and that the benefit is not lost after a few nights of missed treatments.
Depression and Sleep Apnea
The link between depression and sleep apnea has long been acknowledged, but for the first time a study has quantified the magnitude of that link in the general population.
For a study in The Journal of Clinical Psychiatry, researchers conducted a telephone poll of nearly 19,000 Europeans and asked them questions regarding sleep quality, breathing-related sleep disorders, mental disorders, and medical conditions. The prevalence of a breathing-related sleep disorder (which includes sleep apnea and disruptive snoring) in the total pool of respondents was 4.6%; 4.3% also had major depression. More than five times as many people with depression had a breathing-related sleep disorder (18%) as people without depression (3.8%). This relationship persisted even after adjusting for breathing-related sleep disorder risk factors such as obesity and high blood pressure.
It is not known whether breathing-related sleep disorders lead to depression or vice versa, but both conditions share some symptoms (excessive daytime sleepiness and cognitive impairment). Some studies have suggested that CPAP may relieve depressive symptoms as well as breathing-related sleep disorders, but more research is needed to determine whether this is merely a placebo effect.
In the meantime, the researchers suggest that people who are diagnosed with either major depression or a breathing-related sleep disorder should also be examined for the other condition.
High Blood Pressure and Sleep Apnea
More than half of people with sleep apnea also have high blood pressure, and, unlike most people, their blood pressure levels do not fall during sleep. In fact, sleep apnea has been shown to be an independent, treatable cause of high blood pressure. One study found that sleep apnea increased the risk of a new diagnosis of high blood pressure four years later. The risk increased by 42% for people who had less than 5 sleep apnea events per hour; by 103% for 5 to 15 events per hour; and by 189% for more than 15 events per hour.
This link between sleep apnea and high blood pressure appears to persist regardless of gender, age, race, and weight. CPAP treatment appears to treat sleep apnea as well as reduce daytime and nighttime blood pressure, according to a recent review article.
Heart Problems and Sleep Apnea
Heart rate tends to slow dramatically during periods of apnea and then rise rapidly when breathing resumes. Some evidence suggests that periods of sleep apnea and low blood oxygen levels, along with persistently high blood pressure, increase the risk of coronary heart disease. This association is being studied. Stronger associations—although not direct cause-and-effect relationships—have been found between sleep apnea and other heart-related problems, as discussed below.
Left Ventricular Hypertrophy and Sleep Apnea.
Researchers have long suspected the link between sleep apnea and left ventricular hypertrophy (a thickening of the muscular wall of the left ventricle that occurs when the heart must work harder to pump blood). Indeed, a recent study found that 88% of the participants with sleep apnea had left ventricular hypertrophy. The researchers used ultrasound to measure heart size in 25 people with severe sleep apnea. After six months, all patients who complied with CPAP therapy had a significant reduction in left ventricular hypertrophy, which is linked to cardiac-related death.
Atrial Fibrillation and Sleep Apnea.
Similarly, sleep apnea is also linked to atrial fibrillation, an abnormal heart rhythm in which the atria (the upper chambers of the heart) quiver chaotically instead of contracting in a rhythmic pattern. Atrial fibrillation can cause blood clots and is a known cause of strokes.
A recent study found that untreated sleep apnea increases the risk that people who have had atrial fibrillation in the past will have a recurrence; the study also showed that CPAP therapy was associated with a reduced risk of recurrence. All participants had atrial fibrillation in the past and were at risk for recurrence; in addition, they had sleep apnea. Atrial fibrillation recurred in 42% of participants who were treated with CPAP, compared with 82% of participants who used CPAP either incorrectly or not at all.>/p>
Heart Failure and Sleep Apnea.
A link also exists between sleep apnea and heart failure (the inability of the heart to pump blood efficiently). The two conditions commonly occur together, and one study suggests that as many as 37% of people with heart failure also have sleep apnea.
A recent study suggests that treating sleep apnea may also have a beneficial effect on heart failure. Researchers assigned 24 people with heart failure and sleep apnea either to continue their current medical therapy or to add CPAP therapy to their treatment regimen. After one month, the CPAP group had significant improvements in daytime blood pressures, heart rate, and heart functioning. The researchers suggest that untreated sleep apnea may prevent the heart from resting at night, placing abnormal stress on the heart.
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