Distressing dreams are something most of us are familiar with – those scary dreams during childhood we never seem to forget or that bad dream after watching a horror film we knew we should have avoided. Now to add to the list of things that keep us up at night, scientists have made a rather unsettling connection between the frequency of distressing dreams (bad dreams and nightmares) and the development of Parkinson's disease later in life.
Reporting in the journal eClinicalMedicine, researchers from the University of Birmingham have found that older men who experience frequent bad dreams or nightmares are twice as likely to go on and develop Parkinson's disease (PD).
“Although it can be really beneficial to diagnose Parkinson’s disease early, there are very few risk indicators and many of these require expensive hospital tests or are very common and non-specific, such as diabetes.” lead author, Dr Abidemi Otaiku, said in a statement. Therefore, there is a need to identify reliable early indicators that may help inform when someone is at risk of developing the disease.
PD is a neurodegenerative disease that causes the progressive loss of brain cells in a part of the brain called the substantia nigra resulting in the reduction of a brain neurotransmitter called dopamine.
Dopamine is involved in the regulation of movement and therefore patients with PD normally exhibit symptoms including slow movement, stiffness of body muscles, and involuntary tremors of certain body parts such as the arms. The onset of these symptoms is normally gradual and worsens slowly over time. However, early on, patients often present with more non-specific symptoms such as sleeping difficulties and memory problems as brain cells start to degenerate years before a PD diagnosis.
Dr Abidemi Otaiku explained to IFLScience "that bad dreams and nightmares developing in later life, in some individuals, are what we call 'prodromal' symptom of Parkinson's disease " meaning that it could be one of the early signs signaling the disease's onset.
Previous research has shown that people with PD experience changes in their dreams, however, no prospective study has looked at the frequency of bad dreams or nightmares and the risk of developing PD later in life.
Now, researchers have addressed the question by analyzing data from a large US cohort study that contained data from 3,818 men over the age of 67 who lived independently and did not have a PD diagnosis at the start of the 12-year study. Throughout the study, the participants were given various different questionnaires including one to assess sleep quality and how often they experience distressing dreams. Those participants that reported distressing dreams at least once per week were followed up at the end of the study to see whether they had developed PD.
After a seven year follow up period, 91 participants had received a PD diagnosis. The researchers found that those who had frequent distressing dreams were twice as likely to go on and develop PD compared to those who did not. Moreover, participants who had frequent distressing dreams during the first 5 years of the study were three times more likely to develop a PD.
These findings suggest that older individuals who experience frequent distressing dreams might be at risk of developing PD later in life before the main symptoms start to appear.
Nevertheless, it is worth noting that the current results do have some limitations. The cohort analyzed only contained older men, and so Dr Otaiku explained to IFLScience that the "main area of research needed in the near future, is to replicate the findings of my study, in larger and more diverse cohorts" that will include women as well.
"It will be interesting to see how this research progresses when researchers begin to unpick the biological changes that are causing these changes to dream content and how this links to the progression of neurological conditions such as Parkinson's," Dr Katherine Fletcher, research communications manager at Parkinson's UK said in a statement on Sky News.
"The more that is known about the earliest signs of the condition and how the brain might be changing, the closer research will get to better treatments and a cure."