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?"
All rights reserved