A sleep disorder that causes people to act out their dreams may be linked to certain brain diseases, according to a recent study.

Researchers from the University of Toronto in Canada found that rapid eye movement sleep is the best current predictor of brain diseases like Parkinson's and Alzheimer's.

"Rapid-eye movement sleep behavior disorder is not just a precursor but also a critical warning sign of neurodegeneration that can lead to brain disease," John Peever, associate professor and lead author of the study, said in a statement. In fact, as many as 80 to 90 percent of people with [rapid eye movement sleep behavior disorder] will develop a brain disease."

The sleep disorder occurs during the rapid eye movement stage of sleep and causes people to act out their dreams, often resulting in injury to themselves and/or bed partner. In healthy brains, muscles are temporarily paralyzed during sleep to prevent this from happening.

For the study, researchers examined the idea that neurodegeneration might first affect areas of the brain that control sleep before attacking brain areas that cause more common brain diseases like Alzheimer's.

"It's important for clinicians to recognize RBD as a potential indication of brain disease in order to diagnose patients at an earlier stage," Peever said. "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."

Researchers said they hope the results of the study lead to earlier and more effective treatment of neurodegenerative diseases.

The findings were recently published in Trends in Neuroscience.