Longevity Briefs: The Strange Link Between Parkinson’s Disease And Sleep-Walking

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

Why is this research important: Imagine waking up in the middle of the night to find yourself attacking a lamp or worse, your spouse. This is the reality for people affected by REM sleep behaviour disorder (RBD). You may know REM sleep as the sleep stage in which we experience dreams. REM sleep is accompanied by a state of paralysis that prevents us from acting out our dreams, but in people with RBD, this paralysis fails to kick in. Intriguingly, people with RDB are at significantly higher risk of subsequently developing Parkinson’s disease. What’s the link?

What did the researchers do: In this study, researchers analysed stool samples from 441 early Parkinson’s disease patients, RDB patients, and first-degree relatives of RDB patients and healthy controls in Hong-Kong. The researchers wanted to study whether there was a relationship between the composition of bacteria in patients’ guts, and the presence of early Parkinson’s or RDB.

Key takeaway(s) from this research: The authors found that the composition of the gut bacteria in patients with RDB shared similar characteristics with those of patients with early Parkinson’s. Compared to controls and RDB relatives, those with early Parkinson’s and RDB had fewer bacteria producing short-chain fatty acids, especially butyrate. These are beneficial molecules that help reduce inflammation, improve gut wall integrity, regulate the immune system and more. The relatives of RDB patients, meanwhile, had increased levels of gut bacteria that promote inflammation. Most of these associations remained true after controlling for confounding factors like constipation (which has a known association with future Parkinson’s risk) and medication.

We know that the accumulation of α-Synuclein, an important protein in the progression of Parkinson’s disease, actually begins in the gut before spreading to the brain. Disruption of the gut microbiome may be a key part of how this spread happens, making the gut ‘leaky’ and kicking off inflammation in the brain. The fact that both RDB patients and their unaffected relatives showed some signs of a disrupted gut microbiome suggests that these changes could occur many years before the onset of Parkinson’s. 

It’s important to note that, since this study only looked at the participants’ status at a single point in time, we don’t actually know how many of these people went on to develop Parkinson’s disease or RDB. Even if we did, we would not be able to establish cause and effect based on this alone – the early stages of Parkinson’s and RDB could be disrupting the microbiome, rather than the other way around. However, animal models suggest that an altered microbiome can indeed promote neurological diseases, and there’s increasing evidence in humans that an unhealthy gut is an early disease predictor, and hopefully also an early target.