ANN ARBOR, Mich. – The first tantalizing clues that chemical imbalances in the brain may be partly to blame for certain life-disrupting sleep disorders are being reported in two new studies by University of Michigan Health System researchers.
In two papers in the July 8 issue of the journal Neurology, the team reports apparent links between deficits in brain chemistry and obstructive sleep apnea (OSA) and REM sleep behavior disorder (RBD). Both are relatively common sleep problems that disturb the slumber -- and daytime behavior -- of millions of Americans.
The patients with the fewest dopamine-producing neurons in the striatum of their brains had the worst RBD symptoms of thrashing, talking and violent flailing while they slept. And patients with the lowest levels of acetylcholine-producing neurons in the brainstem had the most interruptions in their breathing during sleep.
And while the researchers are careful to note that their findings to date can only show a correlation, not causation, between brain chemistry and sleep disorders, they plan further research to explore the relationship.
For instance, the U-M team is recruiting patients with Parkinson's disease for a similar study, to see if brain chemistry disruptions from their disorder may also be linked to sleep problems. Gilman says he and other specialists suspect that sleep disorders may be an early symptom in many cases of Parkinson's disease.
Gilman and his colleagues chose MSA patients as their first subjects for studying sleep disorders and brain chemistry because of their extremely high incidence of OSA, RBD and other sleep problems; their disease's tendency to cause degeneration of certain nerve cells in their brains and spinal cords; and clinical evidence that some of their sleep problems can be successfully treated with medications that replace lost dopamine.
In addition to plaguing MSA patients, sleep disorders are also a fact of life for millions of others. Obstructive sleep apnea, in which breathing temporarily stops or diminishes dozens or even hundreds of times during a person's sleep, may affect 3 percent of adults but goes undiagnosed in most of them. Its most notable symptoms are snoring and excessive daytime sleepiness, though it can also affect blood pressure, memory and even reaction time while driving.
REM sleep behavior disorder, meanwhile, occurs less often but is outwardly 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. RBD can endanger the sleeping person, or his or her bed partner,
"Usually, while we sleep, our brains keep our hearts and lungs going automatically -- while disabling the muscles that might otherwise let us unconsciously act out our dreams," Gilman explains. "But many people, including most MSA patients, have sleep disorders that close off their airway and interrupt their nighttime breathing, as in obstructive sleep apnea, or cause them to thrash, talk and walk about, as in REM sleep behavior disorder."
The precise causes of these problems are unknown, although obesity is known to be involved in OSA. None of the participants in the newly published studies were obese, and the control subjects were matched with the MSA patients by age and gender.
