Scientists have found the first clues that abnormalities in brain chemistry may contribute to obstructive sleep apnea and rapid-eye-movement behavior disorder, according to 2 articles in the July 8th issue of Neurology.

The American team used 2 types of neurochemical brain scans and detailed sleep studies to evaluate 13 patients with multiple system atrophy (a rare degenerative neurological disease almost always accompanied by severe sleep disorders) who had both sleep apnea and rapid-eye-movement behavior disorder. Investigators also evaluated 27 healthy matched controls.

The patient group had a far lower density of neurons producing dopamine and acetylcholine. As the deficiency became more severe, the sleep disorders worsened. The patients with the fewest dopamine-producing neurons in the striatum had the worst rapid-eye-movement behavior disorder symptoms of thrashing, talking and violent flailing during sleep. Patients with the lowest levels of acetylcholine-producing neurons in the brainstem had the most events of apnea during sleep.

Although the authors noted that the new data only show a correlation, not causation, between brain chemistry and sleep disorders, they plan further research to explore the apparent relationship.

“It’s exciting to be able to show this major neurochemical deficit for the first time and confirm what others have suspected,” said lead author Sid Gilman, M.D. “We don’t yet 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.”

For instance, the same research team is recruiting patients with Parkinson’s disease for a similar study to see if brain chemistry disruptions associated with the disorder may also be linked to sleep problems. Gilman said that he and other specialists suspect that sleep disorders may be an early symptom of Parkinson’s disease in many patients.