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.