Researching a Bad Night’s Sleep

Sleep research for Parkinson's disease shows importance of dopamine and hypocretin

(RxWiki News) A poor night’s sleep can leave you with a hazy outlook on life, fatigued during the day and coping with numerous related health issues. For those with Parkinson’s disease (PD), getting a good night's sleep is even more important.

Lack of sleep is a common problem that may be caused by factors associated with Parkinson's disease itself.

A recent study investigated the impact of two impaired neurotransmitters on sleep disturbances in patients with PD. The researchers concluded that it is likely that degeneration in both neurotransmitters, dopamine and hypocretin, affects sleep and wakefulness.

"Seek support for sleep disturbances from your doctor."

Christian Baumann, MD, of the Department of Neurology, University Hospital, Zurich, Switzerland, and fellow researchers, performed a small study with 10 controls and 20 PD patients who were in various stages of the disease. The neurotransmitters investigated are dopamine, a neurotransmitter that controls the brain's reward and pleasure centers and helps regulate movement and emotional responses, and hypocretin, a neurotransmitter that regulates arousal, wakefulness and appetite.

The sleep laboratory test results and cerebrospinal fluid levels of the PD patients were compared with results from the controls and ten narcolepsy with cataplexy patients from a previous study. 

Cataplexy is a sudden muscular weakness that can be brought on by strong emotions in patients with narcolepsy, a neurological sleep disorder. Usually speech is slurred and vision is impaired while hearing and awareness remain normal.

Narcolepsy with cataplexy patients are known to experience a significant loss of hypocretin, making them excessively sleepy during the day.

PD is a central nervous system disorder that causes people to experience tremors, slowness of movement and problems with balance and coordination. The disease mostly affects people over age 50, is progressive in nature and is caused by a loss of the nerve cells that produce dopamine.

Of the 20 PD patients, ten were in advanced stages of the disease and ten were in early stages of the disease. The advanced patients had more than nine years of diagnosis and the early patients had less than six years of diagnosis.

Precautions were taken to eliminate false data including the elimination of stimulants, sleep aids and hypnotic medication.

Sleep levels and activity logs were kept for two weeks prior to the test to rule out sleep deprivation, and neurological assessments were performed in all patients. A Mini Mental State Examination was used to rule out dementia.

Overnight polysomnography (PSG), a sleep study test that records the biophysiological changes that occur during sleep, was conducted and the number of limb movements per hour was assessed.

A Multiple Sleep Latency Test, a sleep disorder diagnostic tool used to measure start of a daytime nap until first signs of sleep, was executed. The test included four sleep opportunities every two hours and was started after completion of PSG.

The researchers found that night time sleep was the most disturbed in advanced Parkinson's patients, followed by those with narcolepsy and the least disturbed in early Parkinson's patients

Excessive daytime sleepiness was found most in narcolepsy patients and correlated with falling levels of hypocretin in the Parkinson's patients. Some patients with PD were seen to have hypocretin levels that decreased with length of their having the disease.

Dopamine deficiency is known to be linked to poor sleep while the results of this study suggest that a disruption of hypocretin contributes to excessive daytime sleepiness. The effect is measurable even when hypocretin cell loss is partial in diseases like PD.

The study was published in the July issue of the Journal of Sleep Research and funded by a competitive grant from the Swiss Parkinson Foundation. All authors reported no conflicts of interest.

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Review Date: 
July 9, 2012
Last Updated:
December 20, 2012