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TUESDAY, Feb. 16 (HealthDay News) -- The breathing woes that accompany severe sleep apnea may be counterbalanced by this silver lining: those with the condition report fewer nightmares.
"We found that people with significant sleep apnea have much fewer nightmares. They continue to dream, but they report fewer nightmares," said Dr. Jim Pagel, lead author of a study appearing in the Feb. 15 issue of the Journal of Clinical Sleep Medicine. "It's been a question for a long time about the cognitive effects of sleep apnea. . . This is one of the first studies showing a clear cognitive change with sleep apnea and, surprisingly, it's in a positive direction."
Pagel, who is director of the Sleep Disorders Center of Southern Colorado in Pueblo, added that he hopes the finding will spur more research into this aspect of sleep apnea.
"This makes sleep apnea a little sexier. The thought with apnea is it's heavy-set, snoring males and does horrible things to how long you live and whether you have heart attacks and stroke. It's not very interesting to people," he said. "I think this tie-in to dreams and nightmares makes it a little more interesting."
"This gives us more insight and questions to ask patients," said Dr. Carl Boethel, an assistant professor of internal medicine with the Texas A&M Health Science Center College of Medicine and director of the Sleep Institute, Scott & White, in Temple. "If I ask a patient about dream recall and nightmares, they may have more severe sleep apnea."
But this seemingly positive finding is not necessarily so, said another expert.
"It's not a good thing," said Shelby Freedman Harris, director of the Sleep-Wake Disorders Center at Montefiore Medical Center in New York City.
The findings could indicate a glitch in patients' cognitive processing. "There may be something more serious we need to consider," she said.
People with obstructive sleep apnea experience disruptions in their airflow while sleeping, making it difficult to breathe. The condition is marked by loud snoring, interrupted breathing and sleep disruption, and it can lead to higher rates of chronic disease and even death.
Previous studies had indicated that people with apnea actually had more nightmares. But, Harris said, "there haven't been many studies that have looked at different ranges of apnea. If you have apnea in general, some studies show that you have more nightmares but they haven't broken down into mild, moderate and severe ranges."
This latest study involved about 400 men and women, many of whom had severe sleep apnea, who were hooked up overnight to polysomnography machines and who answered questions on dream and nightmare recall.
Those with worse sleep apnea reported fewer nightmares.
More than two-thirds of people without sleep apnea reported frequent (meaning more than once a week) nightmares, vs. only 43.2 percent of patients with mild obstructive sleep apnea.
About 30 percent of those with moderate sleep apnea reported having nightmares, while only 20.6 percent of those with severe sleep apnea did so.
The authors attributed the findings to interrupted rapid eye movement (REM) sleep, which is usually when nightmares happen.
The patients did register having dreams, however.
Although the basic definition of nightmare requires recall of the dream, Harris suggested that the dreams might actually have been nightmares.
"We have no idea what those dreams were," she said. "They could be having cognitive problems while they're sleeping. Why would people with mild and moderate apnea be having nightmares while more severe cases are not?"
Visit the National Heart, Blood and Lung Institute for more on sleep apnea.