512 Confirmatory Factor Analysis of the Sleep Inertia Questionnaire in a Clinical Sample with Sleep Disorders

Abstract Introduction The Sleep Inertia Questionnaire (SIQ) was developed and validated in patients with mood disorders to evaluate difficulties with becoming fully awake after nighttime sleep or daytime naps in a multidimensional manner. However, few data are available regarding its psychometric properties in clinical samples with sleep disorders. Methods 211 patients (43.0±16.4 years old, 68% female, 17% minority) evaluated at the Behavioral Sleep Medicine (BSM) program of Penn State Health Sleep Research & Treatment Center completed the SIQ. All patients were diagnosed using ICSD-3 criteria, with 111 receiving a diagnosis of chronic insomnia disorder (CID), 48 of a central disorder of hypersomnolence (CDH), and 52 of other sleep disorders (OSD). Structural equation modelling was used to conduct confirmatory factor analysis (CFA) of the SIQ. Results CFA supported four SIQ dimensions of “physiological”, “cognitive”, “emotional” and “response to” (RSI) sleep inertia with adequate goodness-of-fit (TLI=0.90, CFI=0.91, GFI=0.85, RMSEA=0.08). Internal consistency was high (α=0.94), including that of its dimensions (physiological α=0.89, cognitive α=0.94, emotional α=0.67, RSI α=0.78). Dimension inter-correlations were moderate to high (r=0.42–0.93, p<0.01), indicating good construct validity. Convergent validity showed moderate correlations with Epworth sleepiness scale (ESS) scores (r=0.38) and large correlations with Flinders fatigue scale (FFS) scores (r=0.65). Criterion validity showed significantly (p<0.01) higher scores in subjects with CDH (69.0±16.6) as compared to those with CID (54.4±18.3) or OSD (58.5±20.0). A SIQ cut-off score ≥57.5 provided a sensitivity/specificity of 0.77/0.65, while a cut-off score ≥61.5 provided a sensitivity/specificity of 0.71/0.70 to identify CDH vs. ESS<10 (AUC=0.76). Conclusion The SIQ shows satisfactory indices of reliability and construct validity in a clinically-diverse sleep disorders sample. Its criterion validity is supported by its divergent association with hypersomnia vs. insomnia disorders, as well as its adequate sensitivity/specificity to identify patients with CDH. The SIQ can help clinicians easily assess the complex dimensionality of sleep inertia and target behavioral sleep treatments. Future studies should confirm the best SIQ cut-off score by including good sleeping controls, while clinical studies should determine its minimal clinically important difference after pharmacological or behavioral treatments. Support (if any):