Does your bed mate complain that you fight in your sleep? Do you dream of being chased by wild animals about to devour you? Do you physically try to fend them off? Sleep disturbances, especially when they feature trying to escape from wild animals, are a sign of impending neurodegeneration. People with Parkinson’s often have dreams with physical aggression such as fighting with animals. And people who act out the actions of their dreams have a very high risk of developing Parkinson’s within 10 to 15 years. But the question now is which is the cause and which is the effect. Does early stage neurodegeneration lead to sleep disturbance or is it the sleep disturbance that leads to neurodegeneration?
Rapid Eye Movement (REM) sleep and non REM (NREM) sleep are normal patterns of human sleep. During REM sleep, rapid eye movements are accompanied by a paralysis of the muscles, except for the diaphragm to allow for breathing. In REM sleep behavior disorder (RBD) the sleeper’s muscles are active and he acts out the disturbances of his sleep, sometimes with vocalizations. Periods of RBD can range from mild movements to violent thrashing about, sometimes injuring the sleeper or harming his bed partner. This behavior can also change over time; it can be mild when young progressing to more violent over the years. While it is sometimes observed in younger patients, it affects mostly men over 50. Presently, there are medications to help alleviate some of the problems and permit the sleeper to get a good night’s rest.
Parkinson’s disease has a long period of slow development; it can take years for the symptoms to progress to the point of concern. Symptoms such as depression, anxiety, anemia, constipation and loss of smell can seem to appear independently along with aging without anyone suspecting that they are strong predictors of neurodegeneration or Parkinson’s. Studies of RBD have shown that the sleep disturbance is accompanied by synuclein inclusions in the brain, which are definite precursors to neurodegenerative diseases.
This scenario gives researchers plenty of areas to study–the relationship between RBD and the development of Parkinson’s holds much promise. The first is the potential to test disease predictors i.e. does RBD predict Parkinson’s? Secondly it presents the opportunity to study the long period of development of Parkinson’s with imaging techniques such as trans cranial ultrasound, Single Photon emission computed tomography (SPECT) and dopaminergic imaging. And finally, the potential to develop neuroprotective therapies.
Given the already strong relationship between RBD and neurodegenerative disease, it is important for neurologists and other professionals to identify this as a pre-motor symptom and to use this information to provide serious counseling to the patients who are at risk.