Daytime Sleepiness and Disrupted Circadian Rhythms in PARKINSON’S DISEASE
Sleep problems affect more than half of people with PARKINSON’S DISEASE. Sleep problems may actually be a symptom that predicts the onset of PARKINSON’S DISEASE. People at risk for PARKINSON’S DISEASE have been known to have disturbed sleep and violently act out dreams. But once the disease has been diagnosed, people with PARKINSON’S DISEASE endure even more problems with sleep. Falling asleep may become difficult, staying asleep even more difficult. If sleeping at night is one problem, excessive daytime sleepiness is yet another difficulty. Many articles have been written about sleep and PARKINSON’S DISEASE, yet the underlying causes have resisted simple explanations. PARKINSON’S DISEASE is a very complex neurological disease whose motor symptoms also tend to occur in cycles. Many of the symptoms, no doubt, are interrelated; their effects compounded by each other.
Circadian rhythms define the sleep and wake cycles of all mammals and those rhythms are affected, in part, by the chemical melatonin, which is secreted in cycles by the pineal gland in response to daylight and darkness of the night. Aleksandar Videnovic, M.D. has been studying sleep in PARKINSON’S DISEASE and has released his newest study on the effects melatonin and circadian rhythms on excessive daytime sleepiness in people with PARKINSON’S DISEASE. This study was done at Northwestern University in Chicago, IL and involved 20 subjects with PARKINSON’S DISEASE and 15 age-matched controls. His objective was to determine the relationship between cycles of melatonin and quality of sleep and severity of daytime sleepiness together with other measures of the disease.
All of the subjects were studied in a modified normal environment for over 24 hours with blood samples being taken every 30 minutes. It would be difficult, if not impossible, to do this study without admitting subjects to a clinical setting so every effort was made to maintain as much as possible the normal environmental conditions of their daily lives, including medication schedules, food intake and exercise routines.
While both the control group and the PARKINSON group had no differences in the 24 hour circadian rhythm cycle, the PARKINSON group had diminished rhythms of melatonin release cycles compared to the control group and PARKINSON subjects who reported more daytime sleepiness had significantly lower melatonin rhythm. These results suggest that a dysfunction in circadian rhythms is involved in excessive daytime sleepiness in people with PARKINSON’S DISEASE.
The researchers note that this study is the first to be done in a controlled environment with blood samples taken every 30 minutes, and subjects were able to maintain their regular medications and schedules. They did not find any relationship between the Parkinson medications and the melatonin cycle, but study of people with PARKINSON’S who have taken no medications should also be evaluated. Other areas such as response to light that may be impaired by retinal degeneration due to dopamine or even autonomic dysfunction which is often a part of PARKINSON’S may play a role in the deregulation of the internal “clock” structure. More studies in the future are needed to address these issues.
At the present time, there are therapeutic approaches, such as bright light therapy and melatonin supplements together with structured physical activity programs and good sleep hygiene that may help to regulate the circadian cycles and improve sleep quality to diminish excessive daytime sleepiness.
Videnovic, A., et al; Circadian melatonin rhythm and excessive daytime sleepiness in Parkinson’s disease; JAMA Neurol. 2014 April; 71(4): 463-469;doi:10.1001/jamaneurol.2013.6239
Review by Marcia McCall