London, Dec 6 (IANS): Do you lack a restful sleep and are in the habit of hitting or kicking in your sleep? Beware, according to a study, this could be a sign of a disorder associated with Parkinson's disease, especially in men.

The rapid eye movement sleep behaviour disorder or RBD, which most often affects persons aged 50-70, and more frequently in men than women, is characterised by disturbances in the part of sleep where dreams take place.

While healthy people are relaxed and lie still during dream sleep, people suffering from RBD live out their dreams and during sleep they hit, kick and shout.

The study, published in the journal The Lancet Neurology, showed that men with RBD lack dopamine -- a chemical in the brain that affects emotions, movements and sensations of pleasure and pain -- and have a form of inflammation of the brain.

As a result, their risk of developing Parkinson's disease or dementia when they grow older increases. Parkinson's disease occurs precisely because the group of nerve cells in the brain that produce dopamine stop working.

"These patients have an inflammation of the brain in the area where the dopamine-producing nerve cells are found," said Morten Gersel Stokholm from Aarhus University in Denmark.

Researchers were not previously aware that there is a form of inflammation of the brain in patients who are at risk of developing Parkinson's disease.

"The findings would be used to determine which patients with the sleep disorder will later develop Parkinson's disease. At the same time, this can also help to develop drugs which can stop or slow the development of the diseases," Stokholm explained.

In this study, patients with RBD and no clinical evidence of Parkinson's and cognitive impairment were recruited from tertiary sleep centres in Spain and Denmark and their brain changes were analysed using Positron emission tomography (PET).