A meta-analysis of studies within a 28-year period indicates that a sleep disorder may be early signs of degenerative brain disorders. The fact that there is no cure for either the sleep disorder or subsequent brain disorder makes this interesting, but ultimately useless, information.
Some people suffer from rapid eye movement sleep behavior disorder (RBD), where the subject physically acts out their dreams. Now, you are not supposed to be able to do that because the brain usually locks the body down while dreaming. This is most probably a very practical way of keeping you from knocking your sleep partner’s teeth out or your own while dreaming that you are Neo in The Matrix. The fact that you can move while dreaming probably means that something is not working right in the upper works.
Research analysts are now saying about 90% of cases with people with RBD who lived long enough acquired Parkinson’s disease or a similar condition. This means that people that punch, kick, or leap up while dreaming should probably start planning for the day when they will not be able to control their motor functions. Neurologists are saying that RBD is an early warning sign of alpha-synuclein breakdown, which causes Parkinson’s disease.
However, there is no cure for RBD, so there is no real way to put this insight to any good use at this point. It may come in handy someday but right now it is an effective way of putting the scare on the 10% or so RBD sufferers that will not get some type of degenerative neurological disorder in the future.