Sleep disturbances and severity of Huntington's disease.

We studied sleep functions in two patients with mild and five with moderately severe Huntington's disease. In mild disease there was chorea, but intelligence, mental function, and sleep were all normal. In moderately severe disease, intelligence and mental function were also affected, and there was a sleep disturbance characterized by prolonged sleep-onset latency, increased interspersed wakefulness, and reduced sleep efficiency.