0212 Questionnaire Assessment of Intraindividual Variability in Sleep: Inconsistent Sleep Can Be Worse Than Short Average Sleep

Abstract

Introduction: The consequences of short sleep are welldocumented, but recent evidence indicates that night-to-night consistency in sleep may be just as important. For the current work, we developed an intraindividual variability in sleep (IIV) questionnaire to make IIV measurement possible in single-time-point studies. We investigated whether self-reported IIV explained unique variance in sleep quality and health beyond average total sleep time (TST), focusing on a critical transition period (first semester of college) in which high variability was predicted. Methods: First-semester college students (N=126, Mage=18.28, 75.40% females) completed an IIV questionnaire in which participants indicated their average sleep duration, then estimated how much their sleep duration deviated from their average duration for each day of a typical week. We quantified IIV as the mean day-to-day change in sleep. Participants also completed standard questionnaires on global sleep quality, social jetlag, daytime sleepiness, depression, and stress. Results: Participants reported substantial IIV in their sleep durations (M=1.77 hours, SD=0.86) that was largely distinguishable from measures of social jetlag (r=.25) and average TST (r=-.18). Patterns of IIV differed across race/ethnicities: in white/Asian students, IIV was strongly associated with social jetlag (r=-.44) whereas in underrepresented minority students, IIV and social jetlag were separate constructs (r=-.03), suggesting that fluctuations in the latter group occur across all days of the week. Greater IIV was associated with significantly worse global sleep quality (r=.24, p=.01), stress (r=.20, p=.03), and depression, r=.20, p=.03). These associations were significant after adjusting for average TST, and only marginally reduced when controlling for social jetlag. Conclusion: IIV in sleep/wake patterns can be captured using a questionnaire, and such measurement provides unique explanatory power to understanding sleep quality and mental health. Future research is needed to compare IIV questionnaire data to actigraphy data and to understand the underlying mechanisms by which inconsistent sleep detrimentally affects individuals.