The strongest predictor of whether someone is developing dementia with Lewy bodies — the second most common form of dementia in the elderly — is whether they act out dreams while sleeping, a new study has discovered.
Researchers at the Mayo Clinic report that men in particular are five times more likely to have dementia with Lewy bodies if they experience a condition known as rapid eye movement (REM) sleep behavior disorder than if they have one of the risk factors now used to make a diagnosis, such as fluctuating cognition or hallucinations.
REM sleep behavior disorder is caused by loss of the normal muscle paralysis that occurs during REM sleep. It can appear three decades or more before a diagnosis of dementia with Lewy bodies is made in males, according to the researchers.
The link between dementia with Lewy bodies and the sleep disorder is not as strong in women, they note.
“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 percent of men with dementia with Lewy bodies in our Mayo database did experience REM sleep behavior disorder. So it is a very powerful marker for the disease,” said lead investigator Melissa Murray, Ph.D., a neuroscientist at Mayo Clinic in Florida.
The findings could improve diagnosis, which can lead to beneficial treatment, Murray added.
“Screening for the sleep disorder in a patient with dementia could help clinicians diagnose either dementia with Lewy bodies or Alzheimer’s disease,” she said.
“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 percent of patients with Alzheimer’s disease have a history of this sleep disorder.”
Once the diagnosis of dementia with Lewy bodies is made, patients can use drugs that can treat cognitive issues, Murray said. No cure is currently available.
Researchers at Mayo Clinic in Minnesota and Florida examined magnetic resonance imaging (MRI) scans of the brains of 75 patients diagnosed with probable dementia with Lewy bodies. A low-to-high likelihood of dementia was made upon an autopsy examination of the brain.
The researchers also checked the patients’ histories to see if the sleep disorder had been diagnosed while under Mayo care.
Using this data and the brain scans, they matched a definitive diagnosis of the sleep disorder with a definitive diagnosis of dementia with Lewy bodies five times more often than they could match other risk factors, such as loss of brain volume, which is now used to aid in the diagnosis.
The researchers also showed that low-probability dementia with Lewy bodies patients who did not have the sleep disorder had findings characteristic of Alzheimer’s disease.
“When there is greater certainty in the diagnosis, we can treat patients accordingly,” Murray said. “Dementia with Lewy bodies patients who lack Alzheimer’s-like atrophy on an MRI scan are more likely to respond to therapy — certain classes of drugs — than those who have some Alzheimer’s pathology.”
Source: Mayo Clinic