Non-motor Subtypes of Parkinson's Disease and Sleep Dysfunction.

Parkinson's disease is a syndrome with many clinical presentations. It is often dominated by visible motor symptoms; however, specific nonmotor features, such as cognitive dysfunction, sleep dysfunction, pain, apathy, dysautonomia, depression, and anxiety, enrich the clinical picture significantly. Proposed non-motor phenotypes segregate to central cholinergic, serotonergic, or noradrenergic dysfunctions, and clinical and biomarker-driven studies support these subtypes. Specific sleep problems appear to be associated with specific nonmotor subtypes of Parkinson's disease.