Sleep Apnea Likely if Patients Have Low Energy

August 10, 2000

New York (MedscapeWire) Aug 10 Being low on energy during the day might be caused by trouble breathing while sleeping, even if the affected person doesn't actually feel sleepy, a new study suggests. In fact, doctors and patients may be missing the real cause of some cases of daytime fatigue: a potentially serious but treatable condition known as sleep apnea. The finding, in the August issue of Chest, demonstrates that patients with undiagnosed sleep apnea don't always describe their symptoms using the term sleepiness that doctors are currently trained to listen for. In effect, the words that patients use may get in the way of the doctor's initial diagnosis. But, the paper says, if patients who are fatigued but not sleepy have laboratory sleep tests, they may show the interrupted breathing patterns of sleep apnea.

"Sleep apnea is a common and underdiagnosed condition in which breathing stops temporarily dozens or even hundreds of times a night. It can have an important impact on a person's productivity, quality of life and health if not treated," says Ronald Chervin, MD, MS, assistant professor of neurology at the University of Michigan in Ann Arbor. "Our data suggest that physicians can't rule out sleep apnea simply because their patients deny having the classic symptom of sleepiness."

The study points out how important it is for physicians to listen carefully to how patients describe their problems. In fact, Chervin made the finding by "listening" to patients both their words and their sleep patterns. He reviewed survey answers and sleep test results from 190 people who had been referred by their regular physicians for sleep studies at the University of Michigan's Michael S. Aldrich Sleep Disorders Laboratory, where Chervin is director.

The subjects or their physicians suspected a sleep disorder, so these individuals don't represent the general population. But the results from their sleep tests, and their answers to questions about how they felt, yield surprising trends that may be important to doctors and the patients who haven't yet sought help for problems with getting a good night's sleep.

In all, 73% of the study's subjects said they suffered from sleepiness, fatigue, tiredness, or lack of energy often or almost all the time. But when the 4 descriptive terms were compared independently, less than half the patients reported feeling sleepy often or always, and 62% said they lacked energy often or always, 57% reported problems with fatigue, and 61% said they felt tired. Women were more likely to describe such symptoms.

Asked which of the symptoms was most significant to them, more patients chose "lack of energy" than any other problem, and almost twice as many chose it than chose "sleepiness." Chervin and colleagues also asked subjects which symptom most kept them from accomplishing what they wanted to do during the day. Forty-four percent said lack of energy, while only 16% said sleepiness.

Women in the study reported all 4 symptoms more than men did. They were 4 times as likely to say they had a lack of energy, and 3 times as likely to state they felt tired during the day. Chervin theorizes that men may be culturally less willing to admit any of the problems asked about in the survey. Only when told they had to choose 1 of the symptoms did the men show similar rates of complaint as women. But, Chervin adds, there may be some neurophysiological differences in the way men and women perceive the effects of poor sleep.

All the subjects in the study came to the University of Michigan sleep lab to have a nighttime sleep test, followed by a daytime examination called a Multiple Sleep Latency Test that measured how quickly they started napping in a dark room. In the overnight tests, electrodes recorded the subjects' sleep stages, a blood oxygen-level sensor was used, and monitors kept close track of their breathing patterns.

To be included in the analysis, subjects had to have at least 5 episodes of absent or diminished breathing per hour in the nighttime test, and could not have narcolepsy, which is associated with excessive daytime sleepiness and involuntary sleep. The results showed that no matter how severe the sleep apnea was, patients were likely to describe their symptoms similarly. Participants with worse apnea (more than 15 interruptions per hour) reported their symptoms and named the most significant one in about the same percentages as the entire group. The study was funded by the National Institute of Neurological Disorders and Stroke.

"These results suggest that patients who deny being sleepy may not be as unlikely to have sleep apnea as is sometimes assumed," Chervin says. "We need more research, in the broader population, on relationships between symptoms patients report and the results sleep tests."

In addition to sleepiness or tiredness during the day, another symptom of sleep apnea is snoring, which is nearly always present. The most common form of the disease is called obstructive sleep apnea, in which the upper airway in the throat becomes obstructed. Breathing stops or diminishes for periods of 10 seconds to a minute or more.

Often, apnea is worsened by excessive weight, having oversized tonsils, or having other structural or neurological problems in the upper airway. There is growing evidence that it may cause high blood pressure, heart attack, heart arrhythmia, stroke, and cognitive problems.

But people with apnea often don't know they have it, because they don't seek help for what they might think is an unsolvable problem. One large epidemiological study suggested that as many as a quarter of all men and 9% of women may have breathing problems at night. Far fewer fit the common definition of obstructive sleep apnea syndrome, however, mainly because they don't report sleepiness. And doctors who hear complaints of fatigue or lack of energy from patients may first suspect other conditions, such as depression or thyroid deficiency.

Sleep apnea is typically treated successfully by a method called continuous positive air pressure, or CPAP. The patient wears a mask that fits over the nose, and connects by an air hose to a machine, slightly smaller than a shoebox, kept near the bed. The machine takes air from the room, filters it and pumps it to a higher pressure that is transmitted through the nose to the back of the throat, where it splints the throat open.

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