A little-known sleep disorder could hold clues to serious brain diseases.

REM Sleep Behavior Disorder (RBD) affects around 2% of folks over 65 and about 1% of the general population. REM, short for Rapid Eye Movement, is a crucial phase of the sleep cycle, linked to dreaming, memory, and brain health. Normally, during REM, the muscles tend to stay still, preventing dream-related movements.

But for those with REM sleep behaviour disorder, it's a different story. Their muscles act out dreams, signalling potential risks for Parkinson's disease and dementia down the line. Dreams turning into violent actions pose a serious concern for patients and also their partners. Individuals experiencing this find themselves being chased or attacked within their dreams, sometimes leading to physical harm during sleep.

Shockingly, around 60% of patients and 20% of their bed partners have reported injuries stemming from these episodes. Understanding RBD remains a challenge for researchers. While it can come about at any age, it typically begins in one's 40s or 50s. However, for younger individuals, antidepressants have been linked to its emergence.

Interestingly, there's an equal number of cases between young women and men, but as individuals age past 50, men are more commonly affected. RBD isn't just a standalone condition. It has connections to serious neurodegenerative disorders like Parkinson’s disease and dementia with Lewy bodies.

This has raised concerns among scientists, who are investigating whether RBD could serve as an early indicator for these debilitating illnesses. RBD is reported in 25 to 58% of Parkinson’s patients and a staggering 70 to 80% of those with dementia with Lewy bodies.

To gain deeper insights, researchers conducted a long-term study involving 1,280 RBD patients, observing how other health issues developed over time. After 12 years, a staggering 73.5% of those affected developed a related neurodegenerative illness. Factors like irregular motor symptoms, dopamine level abnormalities, and even seemingly unrelated issues like loss of smell or erectile dysfunction were linked to increased risk.

Experts suggest that signs of trouble may appear decades before full-blown symptoms, highlighting the importance of early detection. While treatments remain limited, medications like melatonin and clonazepam offer some relief from symptoms. Hopefully, in the future, the ongoing investigation will shed some light on the complex link between RBD and its potential consequences, and it will allow for better management and understanding.

A version of this story was first published on May 29, 2023