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  • Writer's pictureNatalie Wilcox

The Circadian Rhythm of Parkinson’s Disease

Circadian rhythms are processes that occur at different points throughout the 24 hour day. Many elements of the circadian rhythm are guided by the light-dark cycle and revolve around periods of sleeping and wakefulness. 40-90% of people with Parkinson’s report having sleep issues. One of the most common of which is REM sleep disorder, which often manifests as a loss of normal sleep paralysis. This often leads to many kicks and flails while sleeping that are quickly detected by their bed partners. Sleep disturbances may predate motor symptoms for years before the official diagnosis.

Scientists describe sleepiness as the “buildup of sleep pressure” throughout the day leading to sleep. This “buildup” is reliant on internal homeostatic functions including hormone release, changes in the immune system, and other internal functional changes. At the molecular level, these processes are controlled by a network of ‘clock genes’ that encode factors that determine the body’s natural rhythms.

The sleep disturbances that many people with Parkinson’s experience are due to dysfunctions with their circadian regulations. People with Parkinson's often have disturbed sleep patterns that variate more widely as the disease progresses further. The disturbances extend beyond sleep to changes in the typical regulation of blood pressure throughout the day. Typically, people have low blood pressure in deep sleep in the middle of the night which gradually becomes higher as the person gets closer to waking up. In 71% of people with Parkinson’s, this pattern may not exist or be shifted earlier or later in the night. It has also been found that the ‘clock’ genes that typically regulate the progression of circadian rhythms are frequently dysregulated in Parkinson’s. Further dysregulation has been correlated with an increase in the severity of excessive daytime sleepiness, which could also be contributed to sleep dysregulation and insomnia during the night.

Melatonin is a well-known sleep-related hormone that typically increases before bedtime, however, people with Parkinson’s have less release at night which could further contribute to the insomnia experienced by many. Furthermore, there is dysregulation in Cortisol which may also contribute to daytime sleepiness by reducing wakeful signals during the day.

Now that we have learned some of the ways that the circadian rhythms have been involved with Parkinson’s symptomatology, let's dive into why. We know that Parkinson’s manifests from a decrease in the amount of dopamine that is produced by the Basal ganglia due to neuro

degeneration. Dopamine happens to be one of the main contributing controllers of the suprachiasmatic nucleus, which is the controller of all things circadian rhythm. It helps to coordinate hormone releases and keeps you awake during the day and sleepy at night. However, without its trusty dopamine signals, it might start getting a bit lazy and not sticking to its normal routine. Some people find some relief from the circadian disruptions by taking L-dopa as it takes the place of naturally produced dopamine. As more research is conducted there is hope a more efficient treatment for the circadian effects and sleep effects of Parkinson’s will be developed.



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