TUESDAY, April 15 (HealthDay News) -- Rapid eye movement (REM) sleep behavior disorder -- a condition in which people act out often violent and disturbing dreams -- is associated with anxiety, apathy, lower levels of attention and executive functioning, and symptoms of Parkinson's disease, according to three new studies.

The acting out in people with REM sleep behavior disorder (RBD) occurs because they don't experience the normal muscle paralysis in REM sleep, the stage of sleep when people dream. RBD occurs in about 0.5 percent of the population, most frequently in older males.

"Previous studies have shown that some patients with RBD subsequently develop dementia and/or parkinsonism, which typically reflects a neurodegenerative disorder such as Lewy body dementia or Parkinson's disease," Mayo neurologist and study author Dr. Bradley Boeve said in a prepared statement.

"Our knowledge on the RBD-neurodegenerative disease association is largely based on studies focused on single patients, or small groups of patients, with RBD. There are very few studies that have been carried out on RBD on a large scale. Plus, we currently aren't able to identify which patients with RBD will later develop other features of a neurodegenerative disease and which patients with RBD will not."

In an effort to learn more, Boeve and his colleagues studied 765 people, aged 70 to 89, including about 60 with probable RBD.

Of those with probable RBD, 21 percent had anxiety and 11.5 percent had apathy, compared with 8 percent and 4 percent, respectively, among those without the condition. The participants with probable RBD also had significantly lower scores on neuropsychological measures of attention and executive functioning, such as concentration, decision making, and higher order problem-solving. The researchers also found that 1.8 percent of participants had both RBD and parkinsonism.

The study was expected to be presented Tuesday at the American Academy of Neurology annual meeting in Chicago.

"There is currently no treatment to delay the onset or prevent dementia or parkinsonism in patients with RBD who are destined to develop these neurologic problems in the future," Boeve said. "Our ultimate goal is to use therapies that would delay the onset or prevent these problems from ever developing in patients who have a form of RBD that reflects an evolving neurodegenerative disease. However, much more research is needed to get to that point."

More information

We Move has more about Parkinson's disease.