0185 Fatigue is Attributable to Beliefs and Perceptions Rather than Objective Sleep Quality

Abstract Introduction While it is intuitive to assume that daytime fatigue is a function of sleep quantity and quality, the observed relationship between sleep and fatigue is not so straightforward. Evidence suggests that fatigue is more strongly related to retrospective accounts of sleep quality than to objectively assessed metrics of sleep. The current study explores the relationships between subjectively-reported fatigue with insomnia, dysfunctional beliefs about sleep, and objective sleep metrics, assessed via polysomnography (PSG), in individuals with insomnia symptoms. Methods Within an ongoing study, 63 participants with insomnia symptoms (61.9% female; mean age = 35.61, SD = 7.46) completed measures of insomnia, beliefs about sleep, and fatigue. Participants also provided one night of at-home PSG recording. The YASA sleep-staging algorithm was used to derive sleep onset latency (SOL), wake after sleep onset (WASO), total sleep time (TST), and sleep efficiency (SE) from PSG recordings. Results Fatigue severity significantly predicted dysfunctional beliefs about sleep (r = .456, p < .001) and subjectively assessed insomnia severity (r = .414, p < .001). In contrast, fatigue was not significantly related to SOL (r = .236, p = .074), WASO (r = -.068, p = .601), TST (r = .222, p = .083), or SE (r = .037, p = .781). We compared a regression model with subjective insomnia and beliefs about sleep to a model that also included PSG variables. The subjective-only model explained 27.5% of the variance in fatigue severity (R2 = .275), and the subjective+objective model increased the explained variance to 39.9% (R2 = .399), yielding a modest, statistically significant improvement in model fit (ΔR2 = .124; F(4, 50) = 2.59, p = .048). In the full model, TST was the only significant objective predictor (p = .042). Conclusion Preliminary findings indicate that dysfunctional beliefs about sleep and subjectively-reported insomnia predict fatigue severity better than objectively assessed sleep criteria. This suggests that fatigue, when subjectively reported, is more a function of beliefs and subjective experiences than the objective quality of sleep, although TST did contribute incremental predictive value. Future research should include objective measures of fatigue severity and consider moderators of the sleep/fatigue relationship. Support (if any) NIH/NHLBI 1R01HL173043.