Sleep in Functional Motor Disorders: A Case-Control Polysomnographic Study

Sleep problems are frequent in functional motor disorders (FMDs). Surprisingly, objective correlates of impaired sleep and its relationship to other comorbidities have been understudied, and no polysomnographic study is available. We aimed to map the polysomnographic parameters in the context of self-reported sleep and mood symptoms and search for comorbid sleep disorders in FMD and healthy controls. Thirty-seven patients (mean age [SD], 48.2 [10.6] years) with clinically definite FMD and 37 controls (48.6 [11.2] years) underwent structured medical and sleep history assessment, neurological examination and polysomnography and completed questionnaires for sleep quality, sleepiness, depression and anxiety. In FMD, specific sleep disorders were identified in our cohort, with 32% having restless legs syndrome, 38% clinically significant obstructive sleep apnoea and 8% periodic limb movements in sleep. FMD patients reported worse sleep quality (p < 0.001), higher sleepiness (p < 0.001), depression (p < 0.001) and anxiety (p < 0.001), had longer REM sleep latency (p < 0.001), worse sleep efficiency (p = 0.012) and increased wake ratio (p = 0.013). Furthermore, longer sleep latency (p = 0.030) and decreased REM sleep ratio (p = 0.027) in FMD reached nominal significance before adjustment for multiple comparisons. In FMD, subjective sleep quality positively correlated with depression (ρ = 0.54; p < 0.002) and anxiety (ρ = 0.61; p < 0.001) and subjective sleepiness correlated with depression (ρ = 0.42; p = 0.010). Self-reported measures did not correlate with any polysomnographic parameters. Polysomnography detected sleep structure changes in FMD. Sleep abnormalities, including impairments in REM sleep, should be considered in the management of FMD. Future studies should further explore the role of REM sleep disturbances in the pathophysiology of FMD.