Ires Ghielen

81 Longitudinal relationships between anxiety and motor symptoms Introduction Motor features, such as tremor, bradykinesia, hyperkinesia, rigidity, and gait disturbance have been the main focus in clinical management in Parkinson’s disease (PD) for a long time. However, in the last decades, there is increasing awareness of the high prevalence and daily impact of non-motor symptoms, such as anxiety [1, 2]. More recently, reciprocal interactions between motor and non-motor symptoms are being investigated [2-4], leading to multidisciplinary treatment approaches [5]. One of the most disabling motor features of PD is freezing of gait (FoG), an episodic disturbance of gait pattern that affects up to 60% of PD patients, where they report feeling stuck or glued to the floor [6]. Giladi et al. [7] define FoG as a brief, episodic absence or marked reduction of forward progression of the feet despite the intention to walk, including episodes in which the patient cannot initiate gait and arrests in forward progression during walking (“turn” and “destination” hesitation), as well as episodes of shuffling forward with steps that are millimetres to several centimetres in length. FoG severely affects quality of life and daily functioning and can result in falls and injuries [8, 9]. In clinical observations, the motor feature FoG is often accompanied by non-motor features such as fear of falling (FoF) [6], and cross-sectional studies suggest they may aggravate each other [3, 4]. FoF can be described as a lasting patients’ loss of confidence in balance abilities [10]. With an estimated prevalence in PD of 35-59%, FoF is a permanent health concern inducing avoidance and restriction of activities and social life with a significant impact on the patient’s independence [11]. Anxiety is another non-motor feature of PD which also contributes to reduced quality of life [12]. Anxiety has only recently received attention in the PD literature, despite the estimation that up to 40% of all PD patients experience clinically significant anxiety symptoms [13-15]. It occurs in various forms, such as social phobia, panic disorder, general anxiety disorder (GAD) and anxiety related to medication-induced fluctuations such as wearing-off [13, 16]. Studies about the association between FoF and anxiety in PD is scarce, however, anxiety has been described as a predictor of avoidance behaviour in PD patients with FoF [17]. The interaction between FoG and anxiety has been described in clinical practice as a vicious cycle, where anticipation of a FoG episode can trigger an experience of panic and the resulting increase in anxiety symptoms can in turn, trigger or exacerbate FoG [2, 18]. Recent experimental research supports the notion that anxiety is an 5