Researchers at Boston University have found a link between chronic traumatic encephalopathy (CTE), a devastating neurodegenerative disease associated…
with repetitive head impacts, and rapid eye movement (REM) sleep behavior disorder. The rare disorder, typically associated with Parkinson’s disease, interrupts or disturbs sleep paralysis during REM sleep, when most dreams are experienced. The lack of paralysis causes sleepers to act out vivid and often disturbing dreams by talking, flailing their arms and legs, punching, kicking, grabbing, and more.
“It’s a very rare disorder,” says BU neuropathologist Thor Stein. “Dreams can have very high emotional content, and when a person wakes up thrashing about, they’re really disturbed.”
Although some individuals diagnosed with CTE after death were reported to suffer from sleep dysfunction, the type of disorder and its cause has never been formally explored. Now, in a new study published today in the journal Acta Neuropathologica, Stein and a team of researchers report that 32 percent of contact sports athletes with CTE had experienced the disorder during their life. Only one percent of the general population suffers from REM sleep behavior disorder. It’s the first study to connect repetitive head impacts from playing contact sports with the sleep disorder.
“We didn’t expect to find this disorder as frequently as we did [in athletes with CTE],” says Stein, a neuropathologist at VA Boston Healthcare System, a BU School of Medicine assistant professor of pathology and laboratory medicine, and the corresponding author of the new study.
The BU researchers hypothesized that this surprising increase might be due to exposure to repetitive head impacts. To explore the relationship between contact sports participation, multiple brain diseases, and symptoms characteristic of REM sleep behavior disorder, Stein and scientists at the VA Boston Healthcare System and the BU School of Medicine analyzed the brains of 247 athletes donated to the Veterans Affairs-Boston University-Concussion Legacy Foundation (VA-BU-CLF) Brain Bank.
Since CTE can be diagnosed only after death, the researchers interviewed family members of study participants to find out if they had experienced symptoms of REM sleep behavior disorder during their lives.
“It’s usually the spouse we talk to, but sometimes other close family members, asking them if [their loved one] would act out their dreams, thrashing around in bed. It’s really quite scary for people and their partners, and it can lead to some injury because they’re not able to control their movements-they can hit things around or injure their bed partner,” Stein says.
From interviewing family members, they discovered that a third of the study participants had displayed symptoms of the disorder while they were alive.
“We found that CTE participants with probable REM sleep behavior disorder symptoms had played contact sports for significantly more years than participants without these symptoms,” says study first author Jason Adams, a former medical and doctoral student at BU, who is now at the University of California, San Diego. The odds of reporting symptoms, he says, “increased about 4 percent per year of play.”
“Repetitive head impacts may damage and disrupt cells in the brain’s sleep centers,” Stein says.
The study further examined the brains of those with CTE and REM sleep behavior disorder and found an unexpected…
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