HCRT and Parkinson disease: For example, the early onset of narcolepsy‐like sleep manifestations, such as frequent wakening and daytime sleepiness, in PD patients may originate partially from loss of hypocretin neurons in the hypothalamus, and the rate of loss of hypocretin neurons increases with advancing Braak staging of PD neuropathology (Braak et al., 2003; Thannickal et al., 2007).