Every night, when we go to sleep, we spend a few hours in a virtual world created by our brains, where we are protagonists of a story that we do not consciously create. In other words, we dream.
For most people, dreams are predominantly pleasant, sometimes negative, often bizarre, but rarely terrifying. That’s when we remember them.
However, for about 5% of people, quite memorable and terrifying nightmares (the ones that make you wake up) happen weekly or even every night.
Recent studies show that Parkinson’s patients have nightmares and bad dreams more often than people without the disease.
Research suggests that between 17% and 78% of people with Parkinson’s experience nightmares on a weekly basis.
A study I conducted in 2021 showed that newly diagnosed Parkinson’s patients who have recurrent dreams with “aggressive or action-packed” content experience faster disease progression in the years following diagnosis, compared to those who do not have aggressive dreams.
In this way, my study, as well as similar research, strongly suggests that the dreams of people with Parkinson’s can predict future health outcomes.
It made me wonder if the dreams of people who don’t have Parkinson’s can also predict future health outcomes. My latest study, published in The Lancet’s eClinicalMedicine journal, shows that they can.
Specifically, it showed that the development of frequent nightmares or bad dreams at an older age can be an early warning sign of impending Parkinson’s disease in otherwise healthy people.
I analyzed data from a large American study that contained data collected over 12 years from 3,818 older men who lived independently.
At the start of the study, they filled out a series of questionnaires — one of which included a question about nightmares.
Participants who reported having nightmares at least once a week were followed at the end of the study for an average of seven years to see if they were more likely to be diagnosed with Parkinson’s.
In this period, 91 people were diagnosed with the disease.
Those who reported having frequent nightmares at baseline were twice as likely to develop Parkinson’s compared to those who had less than once a week.
Interestingly, a significant proportion of diagnoses occurred during the first five years of the study.
During this period, participants with frequent nightmares were three times more likely to develop Parkinson’s disease.
These results suggest that older adults who will one day be diagnosed with Parkinson’s disease may start having nightmares and bad dreams a few years before they develop the disease’s characteristic symptoms, such as tremors, stiffness and slowness of movement.
The study also shows that our dreams can reveal important information about our brain structure and function and could prove to be an important target for neuroscience research.
However, it is important to note that only 16 of the 368 men with frequent nightmares in this study developed Parkinson’s.
Because Parkinson’s is a relatively rare condition, most people who have frequent nightmares are unlikely to develop the condition.
Still, for those who have other known risk factors for Parkinson’s, such as excessive daytime sleepiness or constipation, the finding could be important: being aware that bad dreams and frequent nightmares (especially when they start suddenly in adulthood) can be an indicator. Parkinson’s disease can lead to early diagnosis and treatment.
One day, doctors may even be able to intervene to stop the disease from developing.
My team now plans to use electroencephalography (a technique for measuring brain waves) to analyze the biological reasons for changes in dreams in people with Parkinson’s.
This could help us identify treatments that can simultaneously treat nightmares and also delay or prevent Parkinson’s onset in people at risk of developing the disease.