AB0926 Autonomic dysfunction in fibromyalgia may be mediated by hypermobility syndrome

Background Neuropsychiatric symptoms are common in Fibromyalgia (FMS). FMS is associated with dysautonomia, particularly orthostatic intolerance, in which there is a phenomenological overlap with anxiety. FMS and dysautonomia are both associated with joint hypermobility (JHS). Objectives To investigate whether signs and symptoms of dysautonomia in FMS are mediated by JHS. Methods Eighteen patients with FMS (all female; mean age 41.06 years) and 19 controls (14 female; mean age 46.42 years) were recruited. JHS was assessed by Brighton Criteria. Multi-systemic symptoms suggestive of dysautonomia were quantified using Autonomic Symptoms and Quality of Life Scale (ASQoLS). Neuropsychiatric symptoms were formally quantified including anxiety level (BAI), depressive symptom level (BDI), panic disorder symptom severity (PDSS) and dissociative experiences (DES). All participants underwent autonomic function testing (9 minute tilt table with heart rate (HR) recording). Statistical comparison between groups was performed using independent samples t test and chi squared as required, correlations were explored using pearson or spearman rho as appropriate. Formal mediation analysis was performed using the method of Baron and Kenny (1), which stipulates that a mediator variable must reduce the statistical relationship between the independent and dependent variable. Results FMS patients had significant objective features of dysautonomia including higher baseline HR (p=.001) and maximal HR during tilt (p=.002) compared to controls and reported significantly higher autonomic symptom burden (p=.001). Symptoms correlated with changes in physiology during autonomic challenge in patients (r=.536, p=.039), but not controls. Across the study anxiety score correlated with absolute change in pre-tilt and average HR during tilt (r=.483, p=.050) and symptoms of dysautonomia (r=.813, p=.001). Dysautonomia symptoms correlated with DES (r=.793, p=.001), PDSS (r=.742, p=.001), interoceptive sensibility (r=.627, p=.007) and BDI (r=.502, p=.040). There was a significant association between JHS and FMS (p=.001), but not generalized joint laxity. Across all participants, dysautonomia symptoms correlated with Beighton score (r=.353 p=.032) and JHS participants reported higher heart rates during autonomic challenge (p=.002) and greater symptom burden (p=.001). The significant relationship between autonomic symptoms and maximum HR during tilt was fully mediated by presence of JHS or FMS (Figure 1). JHS partially mediated the relationship between FMS and increased anxiety scores and fully mediated the relationship between FMS and maximum HR during tilt (Figure 2). Conclusions This study confirms that objective and subjective measures of dysautonomia are more common in FMS, and associated with JHS in this cohort, suggesting a common underlying mechanism which requires further exploration. We highlight the importance of assessing patients with FMS for both JHS and dysautonomia, which may inform further management of this often challenging condition. References Baron RM, Kenny DA. The moderator-mediator variable distinction in social psychological research: conceptual, strategic, and statistical considerations. J Pers Soc Psychol. 1986 Dec;51(6):1173–82. Acknowledgements This work was supported by a MRC CRTF to JAE and supported by BSUH NHS Trust NIHR Clinical Research Facility. Disclosure of Interest None declared