Linking and comparing non-motor symptoms in aging and Parkinson's disease

Abstract Non-motor symptoms (NMS) are an important determinant of Parkinson's disease (PD), both in clinical settings and for patients' quality of life. Some of these symptoms, such as hyposmia, rapid eye movement behavior sleep disorder, depression, and constipation, can precede the diagnosis of PD and could represent clinical biomarkers of developing PD. The NMS rise in frequency and severity with advancing PD as a result of troublesome motor complications. However, normal aging also manifests the occurrence of different NMS, including autonomic deficits, cognitive decline, sleep disorders, and pain. This review discusses the prevalence, pathophysiology, and advances in NMS of different PD stages compared with normal aging.