Skin Conductance Assessment in Parkinson's Disease: A Systematic Review

Multiple biosignals have been investigated in people with Parkinson's disease (PD), but the use of skin conductance measures has not been systematically reviewed. Following the preferred reporting items for systematic review and meta-analysis (PRISMA) standards, we electronically searched for studies investigating the use of skin conductance measures as a biomarker and clinical assessment in people with PD in three databases (2012-2022). The main purpose of the acquisition, the device to record it, as well as preprocessing and analysis methods, were analyzed. Methodological quality was assessed using the strengthening the reporting of observational studies in epidemiology (STROBE) checklist. Twenty-four studies with 940 participants were included. Eighteen acquired the electrodermal activity (EDA), and six the electrochemical skin conductance (ESC). These measures were used as a diagnostic tool to assess autonomic and/or sudomotor disfunction, under-stand decision-making and learning processes and detect gait freezing or nonmotor fluctuations. Fourteen devices recorded EDA and one ESC. Most studies did not preprocess the EDA/ESC signals or apply simple analyses. The EDA was analyzed only in the temporal domain in 23 studies. Analysis of the ESC signal was very limited. Moderate methodological quality was found. There is large heterogeneity not only in the devices to capture skin conductance but also in the signal processing methods. Clinical application of EDA/ESC could be of great value in detecting nonmotor fluctuations or correlating with other observations, but the lack of normative values makes it difficult.