To Sleep... Perchance to Dream?
Photo: Martin Vloet
Could chemical imbalances in the brain be related to sleep disorders? Possibly,
according to recent research by U-M scientists who have discovered links between
brain chemistry and two common conditions — obstructive sleep apnea and REM
sleep behavior disorder.
Sleep disorders are a fact of life for millions of Americans. Up to 3 percent
of adults have some degree of obstructive sleep apnea with repeated episodes
of interrupted breathing during the night that lead to snoring and daytime
sleepiness. REM sleep behavior disorder occurs less often, but is more dramatic.
Patients literally act out their dreams during the rapid-eye movement, or REM,
phase of sleep, moving their arms and legs, getting out of bed, talking and
shouting, and even hitting or punching. REM sleep behavior disorder can endanger
the sleeping person, or his or her bed partner.
These PET scans show differences in brain chemistry
between a normal brain (top) and the brain of a patient with sleep disorders
associated with Multiple System Atrophy (bottom). The normal brain shows
high densities (white and red) of dopamine-producing cells, while MSA
patients have much lower densities (orange and green) of these cells
in the same areas of the brain.
Courtesy: U-M Department of Nuclear Medicine
In research directed by Sid Gilman, M.D., the William J. Herdman Professor
and chair of Neurology in the Medical School, U-M scientists made positron
emission tomography (PET) brain scans and conducted detailed sleep studies
for 13 patients with multiple system atrophy, a rare and fatal degenerative
neurological disease. People with multiple system atrophy were selected for
the study because the disease is almost always accompanied by severe sleep
disorders. Experimental data from studies of these patients — all of whom had
sleep apnea and REM behavior disorder — were compared to data from 17 healthy
U-M researchers found that multiple system atrophy patients had a lower density
of brain cells that produce important neurochemicals called dopamine and acetylcholine.
Patients with the fewest dopamine-producing neurons in the striatum of their
brains had the most severe REM sleep behavioral symptoms. Patients with the
fewest acetylcholine-producing neurons in the brainstem had the most interruptions
in breathing during sleep.
"It's exciting to show this major neurochemical deficit for the first time,
and confirm what others have suspected," says Gilman. "We don't know if we
will find this same effect in patients with other neurological diseases or
in people who are otherwise neurologically well, but these findings are already
suggesting further research opportunities."
Gilman is careful to note that the research findings to date only show correlation,
not causation, between brain chemistry and sleep disorders. U-M scientists
are planning additional research, including a similar study of patients with
Parkinson's disease. Gilman says he and other specialists suspect that sleep
disorders may be an early symptom in many cases of Parkinson's disease.
Research collaborators include Robert Koeppe, Ph.D., U-M professor of radiology;
Ronald Chervin, M.D., associate professor of neurology; Flavia Consens, M.D.,
clinical assistant professor of neurology; Roderick Little, Ph.D., U-M professor
of biostatistics; Larry Junck (M.D. 1976), professor of neurology; Hyonggin
An, graduate student in biostatistics; and Mary Heumann, a research associate
For an expanded version of the story:
Learn more about snoring and sleep disorders