The study involved 393 consecutive patients at an AASM-accredited sleep center. They were evaluated by an overnight sleep study. Their mean age was 50.5 years with a range of 13 to 82 years. Sixty-seven percent of participants were male.
Severe OSA was common. They had a mean apnea-hypopnea index of 34.9 breathing pauses per hour of sleep. An AHI of more than 30 is considered “severe” OSA.
They were asked about dream and nightmare recall frequency. Recall was considered to be “infrequent” when it was reported once a month or less. Recall was “frequent” when it was reported at least weekly.
Results show that about 52 percent of people reported frequent dream recall. Thirty-four percent reported frequent nightmare recall.
The percent of people with frequent nightmare recall decreased as sleep apnea severity increased. Frequent nightmare recall was reported by 71.4 percent of people who did not have OSA and 43.2 percent of people with mild OSA.
The rate of frequent nightmare recall dropped to 29.9 percent in people with moderate OSA. Only 20.6 percent of people with severe OSA frequently recalled nightmares.
Average sleep apnea severity was much higher in people who reported infrequent nightmare recall. They had a mean AHI of 40.3. People who reported frequent nightmare recall had a mean AHI of 24.6.
“The results were somewhat surprising, since nightmares are frequently reported by patients with sleep apnea,” lead author Dr. Jim Pagel told the AASM.
Pagel suspects that the decline in nightmare recall may be attributed to the sleep fragmentation that is caused by OSA. This leads to a reduction in the nightly amount of rapid eye movement (REM) sleep. REM sleep is the sleep stage when nightmares generally occur.
Treating OSA with CPAP therapy leads to increases in the amount of REM sleep per night. This may cause the frequency of nightmare recall to rise when OSA is treated.
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Image by Franco Marconi