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REM Sleep Disorder May Predict Future Cognitive Impairment

September 28, 2014

Mayo ClinicFor most of us, our nighttime dreams make for fun recall and interpretation in the morning. The vivid, movie-like scenes include our movement through a virtual world once we reach the rapid eye movement (REM) stage of sleep.  So that we don’t actually act out those dreams physically, our brains normally put our muscles into a state of paralysis to keep us motionless in our beds. However, this safety restriction malfunctions in about 1 in 200 people, allowing them to mimic their dream movements including flailing, swinging arms and legs which can cause injury to themselves or their bedmates.

Known as Rapid Eye Movement Behavior Disorder (RBD), it is often associated with neurodegenerative disorders such as Parkinson disease, Alzheimer’s disease and dementia, especially in the elderly. Two recent research papers, based on data from the Mayo Clinic Study of Aging, have tried to understand not only the association of RBD and brain disorders but if RBD symptoms can be an accurate early predictor of future neurodegeneration.

In a 2012 study using the Mayo Sleep Questionnaire, researchers at Mayo Clinic followed 44 volunteers who had tested positive for probable RBD over four years to watch for signs of mild cognitive impairment (MCI), an early warning sign for several neurodegenerative disorders.

They found that 34% of those with probable RBD developed MCI or Parkinson disease within four years, a rate 2.2 times greater than that of a healthy population of similar age but with no symptoms of RBD.

“Understanding that certain patients are at greater risk for MCI or Parkinson’s disease will allow for early intervention, which is vital in the case of such disorders that destroy brain cells. Although we are still searching for effective treatments, our best chance of success is to identify and treat these disorders early, before cell death,” said co-author Brad Boeve, M.D., a Mayo Clinic neurologist.

As a follow-up study, Dr. Boeve and his team tested the cognition of a different population of 599 Mayo aging study participants, (median age 63.8), using the Cogstate brief battery, including Detection (DET) – measuring simple reaction time, Identification (IDN) – measuring choice reaction time, One Card Learning (OCL) – measuring visual learning, One Back test (ONB) – measuring working memory and attention, and the Groton Maze Learning Test (GMLT) – measuring spatial working memory. In addition, the levels of alertness and sleepiness of the participants were rated by their close family members.

Researchers found that those rated as more alert required less time to complete the five cognitive tests while accuracy remained constant.  At the same time, participants who had a higher sleepiness score took more time to finish the IDN test.

The study has been published in Alzheimer’s and Dementia, the journal of the Alzheimer’s Association.

“These findings suggest that alertness and daytime sleepiness are associated with cognitive performance in cognitively-normal individuals,” wrote the study authors. “Longitudinal analyses are needed to determine if these sleep related features are predictive of future cognitive decline in this age group.”

Questions or comments? Please contact Dan Peterson