Adults who experience frequent bad dreams and nightmares may be on their way to developing Parkinson’s disease, a study suggests.

Previous studies have shown that older people who have Parkinson’s disease are quite likely to experience frequent bad dreams or nightmares.

But now experts from the University of Birmingham think there is evidence that regular bad dreams could be an early warning sign for developing the condition.

Lead author Dr Abidemi Otaku, from the university’s Centre for Human Brain Health, said “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.”

The new study used data from 3,818 men aged 67 years or over from the US Osteoporotic Fractures in Men Study.

None of the men had Parkinson’s at the start of the research and were asked about the frequency of distressing dreams.

People reporting bad dreams at least once per week were then followed up at the end of the study to see whether they were more likely to be diagnosed with Parkinson’s disease.

During a seven year follow-up, 91 cases of Parkinson’s were diagnosed, most within the first five years of the research.

Those men with frequent bad dreams during the first five years were more than three times as likely to go on to develop Parkinson’s.

Experts now plan to use electroencephalography (EEG) to look at the biological reasons for dream changes.

They will also look at extending the research to larger groups of people of both sexes and different backgrounds, and to other neurodegenerative diseases such as Alzheimer’s.

Dr Katherine Fletcher, research communications manager at Parkinson’s UK, said: “We know that many people with Parkinson’s experience sleep and night-time problems.

“While they can be experienced at any stage, research has often focused on those symptoms that may appear in the early stages of the condition, before diagnosis, as they may help us to predict who will develop Parkinson’s in the future.

“Previous research has shown that one particular sleep problem, known as rapid eye movement (REM) sleep disorder, where dreams are acted out, has been linked to a higher risk of Parkinson’s.

“It is estimated that over 70% of those with REM sleep disorder will go on to develop the condition, although having this disorder alone is not enough to predict a future diagnosis.

“Previous studies have also shown that the dreams of people with Parkinson’s can include more aggressive content, being overall more vivid and nightmarish, than those of people without the condition. There is also evidence that bad dreams might be associated with later cognitive decline.

“This new study provides further evidence that changes to sleep might be an early sign of Parkinson’s, in this case linking bad dreams to increased risk of people going on to develop the condition.

“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.

“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.

“This is of vital importance to the estimated 145,000 people currently diagnosed with Parkinson’s in the UK.”

The study was published by eClinicalMedicine.