Predictors of quality of life in dystonia – a longitudinal study

Objective: To determine the impact of physical and psychiatric morbidity on health-related quality of life (HR-QoL) in a large, international, multi-centre cohort of isolated dystonia patients over two years. Background: Depression, generalized anxiety disorder (GAD) and social anxiety disorder (SAD) occur frequently in patients with dystonia [1-6]. HR-QoL not only relates to physical but also psychological aspects of the disorder [1,2]. The aim of this study was to evaluate long-term predictors of HR-QoL in dystonia. Method: 603 isolated dystonia patients (mean age: 55.6 ± 12.5 years, female n=404) were prospectively enrolled in the Dystonia Coalition study, assessed at baseline and after one and two years. HR-QoL (RAND 36-Item Health Survey), severity of depression and GAD (Hospital Anxiety and Depression Scale), and SAD (Liebowitz Social Anxiety Scale) were evaluated. Dystonia severity and dystonic tremor were examined using a standardized video protocol and the Burke-Fahn-Marsden Dystonia Rating Scale. Predictors of HR-QoL were obtained from eight cross-lagged path models (Bonferroni corrected alpha ≤ 0.006) and a latent class growth analysis (LCGA). Results: Higher depression scores at baseline predicted lower HR-QoL on all eight subscales after two years (all p ≤ .001). Higher anxiety scores at baseline predicted lower QoL related to general health, pain and emotional well-being, whereas higher social anxiety scores predicted higher pain-related QoL after two years (all p≤ 0.006). Dystonia severity at baseline predicted HR-QoL in the context of social functioning (p = 0.002). The presence of dystonic tremor, age and gender did not predict HR-QoL. LCGA revealed two latent classes, distinguished by the HR-QoL that was reported across the three time points. Class 1 (66%) reported a consistently higher level of HR-QoL that was susceptible to depression and SAD, whereas class 2 (34%) reported a consistently lower level of HR-QoL that was susceptible to GAD. There was no relationship between patients’ reports of quality of life in both classes and dystonia severity, age and gender. Conclusion: The most potent predictors of HR-QoL in isolated dystonia are depression followed by GAD, whereas dystonia motor severity only predicts social functioning. Dystonia patients with higher levels of anxiety have lower HR-QoL than patients with depression and SAD. To improve long-term HR-QoL in dystonia, depression and anxiety should be specifically targeted. References: 1. Slawek J, Friedman A, Potulska A, et al. Factors affecting the health-related quality of life of patients with cervical dystonia and the impact of botulinum toxin type A injections. Funct Neurol. 2007;22(2):95-100. 2. Lewis L, Butler A, Jahanshahi M. Depression in focal, segmental and generalized dystonia. J Neurol. 2008;255(11):1750-1755. 3. Gundel H, Wolf A, Xidara V, Busch R, Ceballos-Baumann AO. Social phobia in spasmodic torticollis. J Neurol Neurosurg Psychiatry. 2001;71(4):499-504. 4. Kuyper DJ, Parra V, Aerts S, Okun MS, Kluger BM. Nonmotor manifestations of dystonia: a systematic review. Mov Disord. 2011;26(7):1206-1217. 5. Moraru E, Schnider P, Wimmer A, et al. Relation between depression and anxiety in dystonic patients: implications for clinical management. Depress Anxiety. 2002;16(3):100-103. 6. Fabbrini G, Berardelli I, Moretti G, et al. Psychiatric disorders in adult-onset focal dystonia: a case-control study. Mov Disord. 2010;25(4):459-465.