People who physically act out their dreams while sleeping have a
significantly increased risk of developing a specific kind of dementia, a new
"Dementia with Lewy bodies" is the second most common form of dementia in the
elderly. A Lewy body is an accumulation of a type of protein in the brain. Lewy
bodies are often seen in people with Parkinson's and Alzheimer's disease,
according to the US National Institute of Neurological Disorders and Stroke.
For the new study, Mayo Clinic researchers examined the medical records of 75
patients diagnosed with probable dementia with Lewy bodies. They concluded that
people are five times more likely to develop this type of dementia if they have
a condition called "rapid eye movement (REM) sleep behaviour disorder" than if
they have one of the risk factors currently used to make a diagnosis, such as
hallucinations or significant fluctuations in attention or alertness.
Normally, people don't move during REM sleep, which is a normal stage of
sleep that occurs many times during the night. But during REM sleep, people with
REM sleep behaviour disorder appear to act out their dreams with abnormal vocal
sounds and movements.
The link between REM sleep behaviour disorder and dementia with Lewy bodies
was stronger in men than in women, according to the study presented Thursday at
the American Academy of Neurology's annual meeting, in San Diego.
In men, REM sleep behaviour disorder can appear three decades or more before
they are diagnosed with dementia with Lewy bodies, the researchers noted.
"While it is, of course, true that not everyone who has this sleep disorder
develops dementia with Lewy bodies, as many as 75 to 80% of men with dementia
with Lewy bodies in our Mayo database did experience REM sleep behaviour
disorder. So it is a very powerful marker for the disease," study lead
investigator Melissa Murray, a neuroscientist at Mayo Clinic in Florida, said in
a Mayo news release.
She said these findings could improve diagnosis and treatment of this type of
"Screening for the sleep disorder in a patient with dementia could help
clinicians diagnose either dementia with Lewy bodies or Alzheimer's disease,"
"It can sometimes be very difficult to tell the difference between these two
dementias, especially in the early stages, but we have found that only 2 to 3%
of patients with Alzheimer's disease have a history of this sleep disorder."
There is no cure for dementia with Lewy bodies, but there are drugs that can
treat some of the symptoms.
While the study found a link between REM sleep behaviour disorder and
dementia, it did not prove a cause-and-effect relationship.
The data and conclusions of the study should be viewed as preliminary until
published in a peer-reviewed journal.
The US National Institute of Neurological Disorders and Stroke has more about