Ires Ghielen

23 BAI factor analysis in PD patients Introduction Despite a high prevalence and a major impact on daily functioning and quality of life in patients with Parkinson’s disease (PD), anxiety has only recently attracted scientific attention. Estimates suggest that 40-50% of PD patients experience clinically relevant symptoms of anxiety [1, 2], and approximately one third suffers from an anxiety disorder as specified by the Diagnostic and Statistic Manual of mental disorders (DSM) IV-TR criteria [1-4]. Generalized anxiety disorder, social phobia and anxiety disorder not otherwise specified (NOS) are most frequently diagnosed in this population [2, 3, 5]. Anxiety disorders are more common in PD patients than in the general population, in primary care clinics or in patients with other chronic medical conditions, where prevalence rates vary between 5 and 11% [4]. Anxiety in PD patients is associated with increased subjective motor symptoms [6], more severe gait problems [7], dyskinesias [7], freezing [8], motor response fluctuations [6], and a decrease in health-related quality of life [9]. In clinical practice, anxiety disorders are often underdiagnosed in PD patients [10]. In a large proportion of patients with PD that report clinically relevant anxiety, the symptoms do not meet the criteria of a discrete DSM-IV disorder and are therefore classified as an anxiety disorder NOS [3]. This suggests that anxiety disorders may have an atypical presentation in this population. The poor recognition of anxiety might also be explained by the overlap and interaction with PD-related motor and non-motor symptoms, such as depression, motor symptoms and autonomic failure. An improvement of the diagnostics of anxiety in PD could be aided by an in-depth study of the symptom dimensions covered by self-report questionnaires such as the Beck Anxiety Inventory (BAI) [11] and their relatedness to other motor and non- motor symptoms. Factor analysis is a statistical technique that can help to explore the underlying factors or symptom dimensions covered by a questionnaire. In non-PD samples factor analysis has shown that the BAI comprises cognitive and somatic factors and that the BAI is able to differentiate between symptoms of anxiety and depression [12, 13]. Dimensionality of the BAI in PD patients was only addressed in a single study [14], but no satisfactory factor solution was found, possibly due to the heterogeneity of the study sample. In the present study, we analyzed the symptom dimensions of the BAI within a large sample of PD patients. Secondly, we assessed the overlap of symptoms of anxiety with depression, autonomic dysfunction and motor disability in PD. 2