Nonmotor symptoms more closely related to Parkinson's disease: comparison with normal elderly

Nonmotor symptoms (NMSs) commonly occur in Parkinson's disease (PD). This study sought to explore the domains of NMSs that are more closely related to PD using nonmotor symptoms scale (NMSS), through a quantitative comparison of NMSs' prevalence and NMSS scores of PD patients with normal controls, and clinical implications. We performed a prospective case-control study on PD patients (n=131) and age- and gender-matched normal controls (n=129). We compared NMSs' prevalence and NMSS scores of the PD patients with those of normal controls, and obtained the ratio to identify the domains that were more closely related to PD than normal aging using the NMSS. NMSs are very common among normal elderly as well as PD patients. The domains with the highest ratio of NMSs' prevalence and NMSS scores between the patient and control groups were the miscellaneous, perceptual problems/hallucinations, and sexual function. These three domains were found to be most closely related to PD. NMSs with higher prevalence in PD patients do not always relate more to PD. As NMSs in PD can also commonly occur among the normal elderly, the NMS prevalence should be interpreted with extreme caution. To properly manage the NMSs in PD, it should be kept in mind that avoiding the overestimation of NMSs as part of PD is as important as their early recognition in PD.