Chemical brain imbalances blamed for some serious sleep disorders

Chemical imbalances in the brain may be partly to blame for some life-disrupting sleep disorders, scientists have found.

Brain scans showed people with two kinds of sleep problem - sleep apnoea, in which the person stops breathing while asleep, and REM behaviour disorder (RBD), which can lead to flailing during dreams - produced abnormally low levels of the neurotransmitters dopamine and acetylcholine.

The lower the levels of the chemicals, the worse the sleep problems were, said a team at the University of Michigan Health System.

Writing in the journal Neurology, the team led by Professor Sid Gilman noted a lack of dopamine-producing neurons in a key area of the brain caused RBD symptoms. People with the lowest levels of acetylcholine neurons in an area that controls the muscles of the tongue and upper airway had the most breathing interruptions from sleep apnoea.

Sleep apnoea affects about 3 per cent of adults. While asleep, they may stop breathing hundreds of times. It goes undiagnosed in many people but its symptoms include snoring and excessive daytime sleepiness. It can also affect blood pressure and memory reaction time while driving.

RBD is less common but more dramatic: patients in the "rapid eye movement" stage of a dream will act it out, moving their arms and legs, getting out of bed, talking, shouting and even hitting or punching things. It can endanger the patient and any bed partner.

The discovery was made by using brain-imaging techniques while monitoring muscle movement and the patients' pulse. The group of 13 were compared with the same number of healthy people without sleep problems.

Professor Gilman said: "It's exciting to be able to show this for the first time, and confirm what others have suspected."