Circadian rhythm and sleep in Parkinson's disease: associations with cognition and mood
Wu, Jade Qi
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Parkinson’s disease (PD) is a neurodegenerative disorder associated with motor disturbance and non-motor symptoms (NMS). Although NMS such as sleep and circadian disruption, cognitive impairment, and mood disturbance are prevalent and debilitating, treatments are limited, owing to lack of knowledge about their etiologies and interactions. This project comprised two studies of NMS in mild to moderate idiopathic PD without dementia. The hypothesis of Study 1 was that disruption of rest-activity circadian rhythm contributes to cognitive impairment in PD independently of sleep disruption. Thirty-five participants underwent 7-10 days of actigraphy monitoring, which provided estimates of sleep and circadian functioning, and then neuropsychological testing. Hierarchical regression showed that circadian interdaily stability predicted executive function, visuospatial function, and psychomotor speed, though not memory, independently of sleep. Sleep efficiency independently predicted executive but not other cognitive function. Study 2 examined daily temporal associations between sleep, subjective cognition, and mood (anxiety, positive affect) in PD. Twenty participants used a smartphone app to engage in 14 days of ecological momentary assessment (EMA) of daytime symptoms and subjective sleep quantity and quality. They wore actigraphs for objective sleep assessment. The hypothesis was that sleep quality would predict cognition and mood. Multilevel modeling indicated that subjective sleep quality was bidirectionally associated with mood on a day-to-day basis (i.e., last night’s perceived sleep affected today’s mood, which in turn will affect tonight’s sleep). There was also a trend for subjective sleep quality to predict the next day’s subjective cognitive function. Objective sleep was not associated with any daytime symptoms. Study 1 provided the first evidence that circadian rhythm contributes to cognition in PD independently of sleep. Study 2 indicated that, on a daily timescale, subjective sleep is relevant to mood and possibly cognition in PD, whereas objective sleep is either insufficiently sensitive or not relevant. Together these findings support the use of EMA to investigate small-timescale interactions among NMS, and present circadian rhythms and sleep perception as intervention targets for improving cognition and mood, and ultimately for enhancing quality of life in PD.
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