Discrepancies between self-report and objective sleep outcomes are associated with cognitive impairment and fatigue in people with multiple sclerosis and insomnia

Objectives: The primary aim of this study was to assess the degree to which discrepancies between self-reported and actigraphy-based measures of sleep are associated with specific demographic, disease characteristics, and clinical features in a sample of individuals with multiple sclerosis (MS) reporting clinically significant insomnia symptoms. Methods: Participants were 90 community-based participants with MS and insomnia. Measures included the Pittsburgh Sleep Quality Index (PSQI), Beck Depression Inventory-Fast Screen (BDI-FS), Modified Fatigue Impact Scale (MFIS), and MS Neuropsychological Screening Questionnaire (MSNQ), and wrist actigraphy-derived sleep parameters. Discrepancy scores were calculated by subtracting actigraphy-derived values from PSQI-derived values for sleep latency (SL), total sleep time (TST), and sleep efficiency (SE). Results: Correlations between PSQI and actigraphy-derived values were weak. Significant discrepancies, with moderate-to-large effect sizes, were observed between PSQI and actigraphy for SL, TST, and SE, whereby the PSQI yielded longer SL, shorter TST, and less SE than actigraphy. MSNQ elevations correlated with greater PSQI-actigraphy discrepancies in SL and TST. MFIS elevations correlated with greater discrepancies in TST. Discrepancies were not significantly related to BDI-FS, gender, race, education level, or MS type. Conclusions: Results emphasize the importance of assessing fatigue with sleep, and when feasible, inclusion of both self-report and actigraphy measures.