Disruptions of Circadian Rhythms and Sleep/Wake Cycles in Neurologic Disorders

Throughout evolution, the temporal solar cycles of our rotating planet were internalized via circadian rhythms. These ~24-h internal rhythms drive daily patterns of physiology and behavior. Circadian rhythms are entrained, primarily by the light–dark cycle, and precisely controlled by a so-called master clock located within the suprachiasmatic nucleus (SCN) of the hypothalamus. Disruptions of circadian rhythms have negative consequences on numerous aspects of human health. It is clear that neurological diseases alter circadian rhythms and sleep–wake states. However, there is bidirectional relationship by which disruptions of circadian rhythms and sleep/wake cycles may lead to the progression of neurologic disorders. This chapter will examine the relationship among disruptions of circadian rhythms, altered sleep/wake states, and neurologic disorders. Specifically, this chapter highlights these relationships within Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and stroke.