Brain diseases, such as Parkinson’s and Alzheimer’s, are strongly linked with a sleep order that causes people to act out their dreams, according to researchers at Toronto University.

The sleep disorder, known as rapid-eye-movement sleep behaviour disorder, occurs during REM sleep when sufferers act out their dreams in movements, often resulting in injuries to themselves or their partners. During REM sleep a healthy brain temporarily paralyses your muscles while you sleep, preventing movement.

“Rapid-eye-movement sleep behaviour disorder (RBD) is not just a precursor but also a critical warning sign of neurodegeneration that can lead to brain disease,” says lead author Dr. John Peever. “In fact, as many as 80 to 90 per cent of people with RBD will develop a brain disease.”

“It’s important for clinicians to recognize RBD as a potential indication of brain disease in order to diagnose patients at an earlier stage,” says Peever. “This is important because drugs that reduce neurodegeneration could be used in RBD patients to prevent (or protect) them from developing more severe degenerative disorders.”