Sleep Disturbance as Potential Risk and Progression Factor for Parkinson's Disease.

Sleep disturbances are common and a major source of disability in Parkinson's disease (PD). Primary and secondary insomnia, rapid eye movement sleep behavior disorder (RDB), central sleep apnea, restless legs, and nocturnal akinesia are common sleep disturbances in PD. Prodromal presence of RBD is associated with a more severe motor and non-motor PD subtype implying a significant disease-modifying effect of this parasomnia. Other disease-modifying mechanisms of sleep disturbances in PD include impaired glymphatic clearance, endoplasmic reticulum stress, nocturnal brain deoxygenation and inflammatory processes among others. Impairments of neural circuit switching and imbalance between inhibitory and excitatory neuronal populations are likely responsible for episodic sleep disturbances, in particular RBD. As neural circuits may predict patterns of α-synuclein propagation in the nervous system, impairments of such circuits are of high relevance for PD pathophysiology. Future research is needed to determine whether appropriate treatment for disturbed sleep might slow progression of PD.