An overview of sleep and circadian dysfunction in Parkinson's disease

A relationship between Parkinson's disease and sleep has been recognised for many years. Patients with PD suffer from REM sleep behaviour disorder, excessive daytime somnolence, insomnia, reversal of sleep-wake cycle, and some if not all of these can predate the diagnosis of PD.

There is a fascinating literature emerging on the role the circadian rhythm plays in Parkinson's disease. Circadian rhythm not only regulates our body clock but also has a major bearing on our mood, appetite, bowel habit etc. I started thinking a few years ago about whether abnormalities in circadian rhythm could explain much about the pre-diagnostic phase of PD. I wondered whether the structures in the brain that control circadian rhythm were affected early in PD... I later learned from colleagues that they were not. Now I am starting to wonder whether abnormalities in circadian rhythm are not simply an early manifestation of Parkinson's, but instead an actual risk factor for Parkinson's...

Research shows that normal circadian function is important for maintaining normal processes that go on with cells... it is plausible that when circadian rhythm goes awry brain cells stop clearing proteins so effectively and these then start to accumulate... or that mitcohondria in brain cells don't work so effectively when there is disordered circadian rhythm. Some of my recent research looks directly at the nature of the relationship between circadian rhythm and Parkinson's [watch this space!] but for now I agree with the authors of this review... normalising circadian rhythm may be an important therapeutic target for Parkinson's disease...

- Alastair Noyce

J Sleep Res. 2018 Mar 1. doi: 10.1111/jsr.12673. [Epub ahead of print]
Mantovani S, Smith SS, Gordon R, O'Sullivan JD

http://onlinelibrary.wiley.com/doi/10.1111/jsr.12673/abstract;jsessionid=D053C900C0F2B819BB00734F213B98FB.f02t02

Sleep and circadian alterations are amongst the very first symptoms experienced in Parkinson's disease, and sleep alterations are present in the majority of patients with overt clinical manifestation of Parkinson's disease. However, the magnitude of sleep and circadian dysfunction in Parkinson's disease, and its influence on the pathophysiology of Parkinson's disease remains often unclear and a matter of debate. In particular, the confounding influences of dopaminergic therapy on sleep and circadian dysfunction are a major challenge, and need to be more carefully addressed in clinical studies. The scope of this narrative review is to summarise the current knowledge around both sleep and circadian alterations in Parkinson's disease. We provide an overview on the frequency of excessive daytime sleepiness, insomnia, restless legs, obstructive apnea and nocturia in Parkinson's disease, as well as addressing sleep structure, rapid eye movement sleep behaviour disorder and circadian features in Parkinson's disease. Sleep and circadian disorders have been linked to pathological conditions that are often co-morbid in Parkinson's disease, including cognitive decline, memory impairment and neurodegeneration. Therefore, targeting sleep and circadian alterations could be one of the earliest and most promising opportunities to slow disease progression. We hope that this review will contribute to advance the discussion and inform new research efforts to progress our knowledge in this field.