The Impact of COVID-19 on Parkinson’s Disease: A Case-Controlled Registry and Questionnaire Study on Clinical Markers and Patients’ Perceptions

Figure 1

Venn diagram of the study population and sample size of the questionnaire and registry study groups. The questionnaire study included both the registry and no CISI-PD groups. In total, 179 questionnaires were sent out to potential participants, whereof 66 were filled out completely and included in the questionnaire study, resulting in a response rate of 37%. The no CISI-PD group had the same inclusion and exclusion criteria as the registry study group, apart from lacking the disease severity matching by the Clinical Impression of Severity Index for Parkinson’s Disease (CISI-PD). The data from the group inside the blue circle were analyzed in the registry study.