Ires Ghielen

70 Chapter 4 showed that higher anxiety levels are associated with more motor disability. The presence of more and stronger connections amongst the UPDRS-III items in the high-anxiety group network visually represent this, and contribute to the difference in global strength [3-5, 7, 8]. Visual inspection shows that BAI items 12 and 8 (trembling hands and unsteadiness, respectively) are connected with UPDRS-III items related to tremor, gait, and posture (see figure 1) in both patient groups. In contrast to our hypothesis that connections between motor and anxiety symptoms are stronger in PD patients with more severe anxiety, these connections do not differ in strength between the high-anxious and low-anxious PD groups. As these connections between symptoms appear to be present independent of anxiety level, a possible explanation for the similar connectedness between UPDRS-III and BAI items, is that they both quantify the same symptom, independent of its etiology. For example, BAI item 12 (trembling hands) measures a tremor in the context of anxiety, and UPDRS-III item 20 (resting tremor) measures a tremor in the context of PD symptomatology. However, whether they often appear together as separate symptoms or appear to measure one and the same symptom independent of its etiology cannot be tested here and is therefore speculative [17]. We found significant differences in descriptive and clinical characteristics between the patient groups. The high-anxiety group was older, included more females, and showed significantly more severe motor impairment and cognitive decline. The group difference in cognitive functioning is in line with what is seen in clinical practice. In general, PD patients with cognitive dysfunction are more anxious [18, 19]. The group difference in gender distribution is also in line with clinical practice and previous research, which shows that females show higher levels of anxiety compared to men [20, 21]. In spite of these clear differences in clinical profile, the connections between the motor and anxiety items were similar. This indicates that in this cross-sectional dataset certain motor and anxiety symptoms are intertwined independently of anxiety level and these symptoms are therefore important in the differential diagnosis of anxiety in PD. For example, when motor symptoms are very much apparent, anxiety symptoms might also be more apparent. When these anxiety symptoms mostly include items that appear to represent motor symptoms (such as BAI-items 8 and 12), patients might not be particularly anxious and treatment should be focused more on the motor symptoms.