Ires Ghielen

64 Chapter 4 symptoms in the context of all other symptoms that are included in the network. Using this method, van der Velden and colleagues [11] investigated the influence of motor and non-motor symptoms using time-series data of one PD patient and showed that higher anxiety scores were longitudinally associated with increased rigidity and tremor [11]. To gain more insight in the associations between individual motor and anxiety symptoms cross-sectionally, and to investigate whether these associations depend on the presence of clinically significant symptoms of anxiety, we performed a network comparison analysis on PD patients with high levels of anxiety versus PD patients with low levels of anxiety. We expected a significant difference between high-anxious versus low-anxious PD patients in symptom network architecture, with the high-anxiety group showing significantly stronger associations between motor and anxiety symptoms than the low-anxiety group. Methods Subjects Data were collected during routine clinical assessments at the outpatient clinic for movement disorders of the Amsterdam University Medical Center (Amsterdam UMC), location VUmc, in Amsterdam, the Netherlands, between May 2008 and May 2018. In this period, 649 PD patients were assessed. Patients were clinically diagnosed with idiopathic PD according to the United Kingdom PD Society Brain Bank criteria. A cutoff of 12 on the BAI was used to divide the total patient sample into a high-anxiety and a low-anxiety group [12]. All included patients gave written informed consent to use their clinical data for scientific purposes. Patients with missing data on the motor or anxiety outcome measures were excluded. Measurements To describe the patient groups, age and gender were recorded, as well as total scores on the Mini Mental State Examination (MMSE), and section III of the Unified Parkinson’s Disease Rating Scale (UPDRS-III). Both the MMSE and UPDRS-III were assessed by a neurologist in training.