Military veterans with post-traumatic stress disorder (PTSD) or who experienced a traumatic brain injury have more than double the risk of a rare sleep disorder — called rapid eye movement (REM) sleep behavior disorder — previously reported as a risk factor for Parkinson’s disease, a study finds.
Researchers at the VA Portland Health Care System and Oregon Health and Science University, who were responsible for this study, are now planning to explore this association and the incidence of Parkinson’s among veterans with REM sleep behavior disorder (or RBD).
“This is important because, in the general population, RBD has been linked to Parkinson’s disease, and RBD often precedes classic symptoms of Parkinson’s by years,” Miranda Lim, MD, PhD, a staff physician at the VA and the study’s senior author, said in a news release.
The study, “Post-traumatic stress disorder increases odds of REM sleep behavior disorder and other parasomnias in Veterans with and without comorbid traumatic brain injury” was published in the journal SLEEP.
RBD is characterized by uncontrolled and violent arm and leg movements, and acting out dreams during sleep. This sleep disorder has been specifically linked to the development of synuclein-related diseases. RBD of no known cause, called idiopathic RBD, occurs in approximately 1% of the general population.
Previous studies suggest that people with RBD are at a greater risk of neurodegenerative disorders — such as Parkinson’s and dementia — with 6.25% of them acquiring an overt neurodegenerative disease within a mean period of 4.6 years. The risk of developing such diseases was also found to progressively increase, from 10.6% after two years to 73.5% after 12 years.
Veterans are at a particularly high risk of traumatic brain injury (TBI) and PTSD, and as such represent a “population enriched for a history of trauma.” Concussions and other mild brain injuries, which many experience during their military service, are also linked to an increased Parkinson’s risk. One study reported that veterans with any kind of traumatic brain injury had a 71% higher likelihood of Parkinson’s than other vets.
Researchers now evaluated veterans’ sleeping patterns according to their pre-existing history of brain injury or other neuropsychiatric trauma, investigating the prevalence of RBD in 394 veterans —mainly male (94%) and middle-aged (54.4 years) — and its association with TBI and PTSD.
Analysis of veterans’ sleep patterns, based on the electrical activity in muscles, found that 9% of them experienced RBD, 7% had higher muscle tone during REM or deep sleep — a condition known as REM sleep without atonia — and 31% had other sleeping problems (parasomnias). This suggested that RBD is considerably more common in veterans than the general population.
They found that veterans with a brain injury or PTSD had a higher incidence of parasomnias. In particular, among those with PTSD or PTSD plus brain injury only 32% and 20% had normal sleeping behaviors, while 56% of these people experienced REM sleep behavior disorder.
Overall, veterans with PTSD had 2.81 and 3.13 times higher odds of RBD and other parasomnias, while those with PTSD plus TBI had 3.43 and 3.22 times higher odds of RBD or other parasomnias.
Given the strong association between RBD and progressive neurodegenerative disorders, it remains to be determined whether RBD and neuropsychiatric symptoms “increases the risk of similar long-term neurologic sequelae [consequences],” the researchers wrote.
“We don’t know whether veterans who have PTSD and higher rates of RBD will go on to develop Parkinson’s, but it is an important question we need to answer,” Lim said. “If you could intervene when people first start to show RBD, maybe you could prevent later symptoms of Parkinson’s.”