Circadian Rhythms in Parkinson’s Disease

Circadian rhythm is a biological process that regulates neuronal, metabolic, and hormonal functions following a 24-hour cycle. Parkinson’s disease (PD) is a progressive neurodegenerative disorder, and it exhibits diurnal fluctuations in motor and non-motor symptoms. Recently, increasing attention has been paid to circadian dysfunction in PD patients. This review summarizes the existing research on the circadian rhythms in PD especially endogenous markers, clinical symptoms, and available treatment options.