Investigating subjective and objective sleep in functional neurological disorder using self-reports and actigraphy - A cross-sectional study.

Background Functional neurological disorder (FND) is a frequent and disabling neuropsychiatric condition. Patients frequently report comorbid sleep disturbances; however, the role and aetiology of sleep impairments in FND remain incompletely understood. Methods We assessed sleep quality in a cohort of mixed FND patients and healthy controls (HC). All participants completed the Pittsburgh Sleep Quality Index (PSQI; subjective), whereas patients additionally underwent a 2-week actigraphy (objective). First, we compared subjective sleep quality between groups and assessed the role of comorbid psychiatric symptoms. Secondly, in patients only, we evaluated subjective and objective sleep quality according to clinically meaningful thresholds and examined the inter-assessment concordance (subjective vs. objective measures). Results 26 mixed FND patients (73% female, mean age 38.4y) and 26 age- and sex-matched HC (73% female, mean age 36.5y) were included. We observed significantly impaired subjective sleep quality (sleep efficiency, sleep latency, sleep disturbances, daytime dysfunction, overall sleep quality) in FND compared to HC, whereas symptoms of depression and anxiety appeared as contributing factors. Sleep quality was classified as bad to chronically disturbed in 77% of patients compared to 31% of HC. Across modalities, sleep efficiency qualified as clinically relevant in most patients (62% subjective, 73% objective), whereas we observed a significant inter-assessment discrepancy in sleep latency (p = 0.001) in FND. Conclusion This study depicts sleep impairments in FND patients compared to a healthy control sample and according to clinically meaningful thresholds, in addition to a disparity between subjective and objective perception. These findings suggest sleep as a critical comorbidity in FND, which warrants greater attention.