Sleep and circadian rhythms in α-synucleinopathies-Perspectives for disease modification

The global north is facing an unprecedented rise in the prevalence of neurodegenerative diseases. The increasing incidence of Parkinson's disease is being referred to as a pandemic. The reason for the enormous increase is only partly understood. Lifestyle factors are known to play a role, but they alone cannot account for the surge. One factor that-although being recognized as important-has not been explored in detail so far is the influence of circadian rhythms. Sleep and circadian rhythm disruption are known as key factors in neurodegeneration, and their occurrence during early disease stages suggests a causal role in the pathogenesis. Isolated rapid eye movement (REM) sleep behavior disorder (iRBD) has been identified as a prodromal state of a-synucleinopathies, such as Parkinson's disease, Lewy body dementia, and multiple system atrophy offering a window for insights into the early development of these diseases. Even though REM sleep is the sleep state most pronounced, driven and modulated by the circadian timing system, specific circadian abnormalities have not been described in iRBD. Novel experimental and clinical approaches exploiting the molecular circuitry underlying circadian timekeeping hold promise to disentangle some of the pathophysiologic mechanisms of a-synucleinopathies. In this review, we summarize current knowledge on sleep and circadian rhythm disruptions in a-synucleinopathies with an emphasis on molecular aspects and therapeutic potentials. These insights might contribute to our understanding of the pathogenesis of neurodegenerative diseases and may allow therapeutic interventions addressing the disturbed circadian system at the early stage of disease.

Automated summary

The prevalence of neurodegenerative diseases, particularly Parkinson's disease, in the global north is increasing at an alarming rate, with some even calling it a pandemic. While lifestyle factors are known to contribute, the role of circadian rhythms in these diseases has not been extensively explored. Sleep and circadian rhythm disruption have been found to play a key role in neurodegeneration, particularly during the early stages of the disease. This review summarizes the current knowledge on sleep and circadian rhythm disruptions in neurodegenerative diseases, with a focus on molecular aspects and therapeutic potentials, providing valuable insights into the pathogenesis and potential treatment interventions.