Patients with chronic posttraumatic stress disorder (PTSD) are at increased risk for altered REM sleep without atonia (RSWA), new research suggests.
Atonia is the normal temporary paralysis of arms and legs that occurs during REM sleep; RSWA is characterized by abnormal muscle activity during sleep.
A study of more than 100 civilians showed that those with chronic PTSD, either alone or with REM sleep behavior disorder (RBD), had significantly higher levels of RSWA than a group of their healthy peers.
In addition, higher levels of RSWA were found in the participants with both PTSD and RBD than in those with PTSD only.
"These data provide the first evidence for abnormal RSWA control in [civilian] patients with chronic PTSD," the researchers note.
"This suggests a unique biology in PTSD, which may overlap with that of RBD and could imply a future risk for neurodegenerative disease in PTSD similar to RBD patients," coinvestigator John Feemster, medical student at the Medical College of Wisconsin, Wausau, and research assistant at the Mayo Clinic Center for Sleep Medicine, Rochester, Minnesota, told Medscape Medical News.
Shared Clinical Features
The researchers note that sleep disturbances and "traumatic nightmares" are common symptoms in PTSD.
"Previous studies suggest military combat-associated PTSD and psychiatric illness may share clinical features," including RSWA and idiopathic RBD (iRBD), they add.
RBD includes the presence of RSWA and a history of dream-enacting behavior.
"There's been a suggestion that there's overlap between RBD and PTSD on several levels, including dream enactment sometimes," said principal investigator Erik St. Louis, MD, codirector of Mayo's Center for Sleep Medicine and director of the Mayo Sleep Behavior and Neurophysiology Research Laboratory.
"Acting out of dreams can be quite scary and violent for both patients and their bed partner. In separate research that our group and others have done, we have found that patients with RBD really have significant injury potential. They can fall out of bed or inadvertently injure their spouse or themselves during their sleep," he added.
A case report by researchers including St. Louis and Feemster that was published recently in the Journal of Clinical Sleep Medicine described increased muscle activity in a military veteran who had PTSD and RBD.
Because that study and a few others examined muscle activity in a veteran population, "we wanted to expand on that and include civilians to see if [the findings] were translatable to them as well," Feemster said.
The investigators assessed records from the Mayo Clinic Center for Sleep Medicine's polysomnography database. The current analysis included 18 patients with chronic PTSD only, 18 with both PTSD and RBD, 15 with idiopathic RBD (iRBD), and 51 age- and sex-matched participants to act as the healthy controls group.
In the full group of 102 male and female participants, the average age at baseline was 57.8 years. The average age at diagnosis of RBD or PTSD was 56.2 years and 45.4, respectively.
Levels of RSWA in the submentalis (SM) and anterior tibialis (AT) were analyzed for all participants. Measures used included average SM duration, average AT duration, SM phasic density, SM any density, AT phasic density, AT any density, SM + AT phasic density, SM + AT any density, and tonic density.
After adjusting for multiple comparisons, statistical significance was defined as P < .016.
Results showed significantly greater levels of RSWA on all density measures in the patients with iRBD or PTSD only vs the healthy controls group (all comparisons, P < .016).
Interestingly, the measures did not show elevated RSWA levels in participants with PTSD who were taking antidepressants.
"There's been some suggestion that antidepressant use might drive up muscle activity. Or is it a distinct biological property of the disease? At least from this cross-sectional data, it looks like it is more disease-related because these effects were really independent of the antidepressant medications," St. Louis said.
Greater RSWA levels were shown for those with PTSD plus RBD vs their healthy peers on all measures except for average SM duration (P < .016 for all other comparisons).
The PTSD plus RBD group also had higher RSWA levels on the SM Phasic, AT Any, SM+AT Any, and Tonic RSWA measures vs the PTSD-only group (P < .016 for all.)
"These data provide the first objective evidence for elevated RSWA within the chronic PTSD population that is not associated with previous war combat," Feemster noted.
"I think this is evidence that there is a unique biology of chronic PTSD. This doesn't look like it's just an acute aspect of the disease but it's a chronic effect; and these patients have a biological predisposition, like RBD, to have abnormal increased muscle activity during REM sleep," St. Louis said.
"Another way to see it is: they have a loss of the normal atonia, or paralysis, of REM sleep compared to normal sleepers. It may not be as robust as for RBD itself, but it's somewhere in between totally normal and the complete abnormality or loss of muscle atonia regularly seen in RBD," he added.
The investigators note that more studies are now needed in order "to determine the specific mechanism driving overlap and distinction" between RBD and PTSD plus isolated RSWA.
Commenting for Medscape Medical News, Thomas A. Mellman, MD, director of the Center for Clinical and Translational Research and Stress/Sleep Studies program at Howard University College of Medicine, Washington, DC, called the study "an interesting observation" and noted that similar observations have been made previously, albeit in populations of military veterans.
"There's long been interest in understanding what's going on in terms of REM sleep with PTSD, with various suggestions that there might be some disruption of REM sleep in people developing or who have PTSD," said Mellman, who was not involved with the research.
"For the relationship between PTSD and RBD, there continues to be accumulating evidence that something is going on there, but we don't know for certain what that is," he added.
He noted that there appears to be a similar phenotype between the two conditions, "but whether it's the same pathophysiology, I don't think we know at this point with certainty."
Mellman said this type of research is important because RBD "seems to be an early manifestation of Parkinson's disease or other synucleinopathy dementias" in some individuals.
"There is some evidence that PTSD is a risk factor for degenerative neurologic disease. Whether or not that's a common vulnerability or [that] PTSD itself involves a process that puts people at greater risk, we don't know yet," he said.
The take-home message from the current study is the importance of trying to limit disruption of REM sleep among those with PTSD, said Mellman, noting that there is pharmacotherapy available that can help with that.
"There may also be value in helping people desensitize to their nightmares, and there are psychological methods for doing that as well. The other take-home message is that we need to be attentive to what's going on with these patients as they age, both in terms of their sleep and neurocognitive function," he said.
Overall, Mellman said it's an exciting time for the field. "There is an emerging model of what's going on with sleep and posttraumatic stress disorder that's more coherent than what we've had in the past," he added.
Feemster, St. Louis, and Mellman have disclosed no relevant financial relationships.
American Academy of Neurology (AAN) 2020 Annual Meeting. Abstract S3.009.
Medscape Medical News © 2020
Cite this: Chronic PTSD Linked to Altered REM Sleep Without Atonia - Medscape - Jun 12, 2020.