Bad dreams and nightmares may be one of the earliest signs of Parkinson's disease, research finds.
University of Birmingham, UK, researchers found in a group of older men, people who had frequent bad dreams were twice as likely to be diagnosed with the disease, compared with those who did not.
While previous studies showed people with Parkinson's had nightmares and bad dreams more often than adults in the general population, those experiences had not been considered as a risk indicator.
Lead author, Dr Abidemi Otaiku, of the University's Centre for Human Brain Health, said there were few risk indicators to Parkinson's and many of them need expensive medical tests, or are very common and non-specific, such as diabetes.
"While we need to carry out further research in this area, identifying the significance of bad dreams and nightmares could indicate that individuals who experience changes to their dreams in older age - without any obvious trigger - should seek medical advice," Dr Otaiku said.
The team used data from a US study that had data from a period of 12 years from 3818 older men living independently. At the beginning of the study, published in eClinicalMedicine, the men completed a range of questionnaires, one of which included a question about sleep quality.
Participants who reported bad dreams at least once per week were followed up at the end of the study to see whether they were more likely to be diagnosed with Parkinson's disease.
During the follow-up, 91 cases of Parkinson's were diagnosed. The researchers found that participants who had frequent bad dreams were twice as likely to develop the disease compared to those who did not.
Most of the diagnoses happened in the first five years of the study. Participants with frequent bad dreams during this period were more than three times as likely to go on to develop Parkinson's.
The results suggest that older adults who will one day be diagnosed with Parkinson's are likely to begin experiencing bad drams and nightmares a few years before developing the characteristic features of Parkinson's, including tremors, stiffness and slowness of movement.
The study also shows that our dreams can reveal important information about our brain structure and function and may prove to be an important target for neuroscience research.
The researchers plan to use electroencephalography (EEG) to look at the biological reasons for dream changes. They will also look at replicating the findings in larger and more diverse cohorts and explore possible links between dreams and other neurodegenerative diseases such as Alzheimer's.
The full paper Distressing dreams and risk of Parkinson's disease: a population-based cohort study. Otaiku (2022) was published at eClinicalMedicine (The Lancet). The pre-print can be found here.