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Updated 12:00 noon February 16, 2004



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Does sleeping brain 'wake up' with every snore?

Patients who snore or have other symptoms of sleep apnea often undergo testing in sleep laboratories to measure the number of breathing pauses and arousals that occur while they slumber. But doctors find these tests do not effectively predict daytime consequences suspected to arise from sleep apnea.

Now, neurologists at the U-M Health System (UMHS) and engineers at Altarum Institute in Ann Arbor have discovered evidence that the disruption of sleep in sleep apnea may be much more frequent than the breathing pauses, or apneas, themselves.

In two papers published in the February issue of the journal Sleep, the researchers describe for the first time evidence that, on average, brain waves change with each breath, not just the short periods of the night when apneas occur. Although the data are preliminary, they suggest a whole new thinking in sleep research that eventually might help doctors predict who will suffer consequences of sleep apnea, and who will respond to treatment.

"Complicated studies that require time, money and technical expertise are often performed in sleep laboratories," says Dr. Ronald Chervin, director of the Sleep Disorders Center (SDC) and Michael S. Aldrich Sleep Disorders Laboratory at UMHS.

"The most common reason is to gauge the severity of sleep apnea. A frustrating problem has been that results of these studies have not predicted the behavioral outcomes of sleep apnea very well. That makes us think that maybe we don't have the best laboratory measures; maybe we are not recording some of the most important features of sleep apnea."

Engineers at Altarum applied their long experience in signal pattern detection to develop a novel computer program that measures the extent to which brain wave activity varies on average with the breathing cycle during sleep. The research shows for the first time that, on average, brain wave activity as reflected in the electroencephalogram (EEG) did change with the breathing cycle of the child being studied, even when no pauses in breathing occurred.

Millions of people experience sleep apnea, a condition in which repeated pauses in breathing during sleep cause many arousals during the night. The nocturnal arousals, in turn, are suspected to be an important cause of daytime symptoms: sleepiness in adults, and attention problems or hyperactivity in children.

Typical measures for assessing sleep apnea involve counting the number of times a patient's breathing is obstructed or partly obstructed. But sleep specialists also know that people with sleep apnea often work harder than normal to breathe even in between these episodes.

In addition to Chervin, researchers included registered nurse Deborah Ruzicka of the UMHS SDC and several employees of Altarum.

U-M and Altarum have filed a provisional patent application on the signal-analysis algorithm used to track changes in the brain during the respiratory cycle. Funding for the study came from the National Institutes of Health, the U-M General Clinical Research Center, and Altarum.

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