How vital is sleep in Huntington's disease?

Huntington's disease (HD) is a fatal neurodegenerative disease caused by an abnormal expansion of a CAG repeat in exon 1 of the HD gene on chromosome 4. The disease runs a debilitating and progressive course with an average survival of 15-25 years after disease onset. HD patients classically develop involuntary movements including chorea, as well as progressive cognitive and psychiatric disturbances, although a number of other features have also been reported, including changes in sleep and circadian rhythms; it is this latter area that forms the focus of this review.