Handgrip strength and relationship with non-motor symptoms in Parkinson's disease

Background Muscle weakness, particularly reduced handgrip strength (HGS), is a prominent clinical feature in Parkinson's disease (PD). While the relationship between motor symptoms and muscle strength has been extensively studied, the connection between HGS and non-motor symptoms (NMS) remains less explored. Objective This study investigates the relationship between HGS and NMS in PD patients, hypothesizing that higher burden of NMS is associated with a reduced HGS. Methods Fifty consecutive PD patients were enrolled and underwent comprehensive neurological and neuropsychological evaluations, 3T MRI scans, routine laboratory tests, and 123 I-Ioflupane SPECT imaging. HGS was measured using a DynEx hand dynamometer, and NMS were assessed using the Non-Motor Symptoms Scale (NMSS). Cognitive function was evaluated with a battery of 18 psychometric tests, and quality of life was assessed using the Parkinson's Disease Questionnaire-8 (PDQ-8). Results Reduced HGS was observed in the majority of PD patients and was significantly correlated with higher NMSS scores, particularly in mood and cognitive domains. Lower HGS was also linked to poorer quality of life. In linear regression models, NMSS remained a significant predictor of HGS even when controlling for age, sex, and Mini-Mental State Examination scores. Conclusions: Our findings suggest that HGS could serve as a valuable biomarker for non-motor symptoms, including depression and cognitive dysfunction, in PD patients. This study underscores the importance of integrating HGS measurements into clinical practice to identify muscle weakness and cognitive impairment, guiding more targeted interventions to improve patient outcomes.