0015 Associations Between Bedtime Procrastination and Circadian Rest-Activity Rhythms Across One Year

Introduction Circadian rest-activity rhythms (RARs) describe the circadian-mediated pattern of physical activity across the day. Alterations in RARs are associated with health concerns, including diabetes, cognitive impairment, and bipolar disorder. However, the sleep behaviors which disrupt RARs are poorly understood. As bedtime procrastination, or the tendency to delay sleep in the absence of external obligations, is associated with delayed and irregular sleep timing, the present study evaluated whether bedtime procrastination was associated with RAR disruptions across 1 year. Methods 96 participants (Mage = 35.8, SD = 9.8) with habitual sleep onset time between 23:00 and 03:00 completed at least two 7-day assessments of wrist-worn actigraphy over the course of 1 year (baseline, 6 months, and 12 months). Participants also completed self-report measures of bedtime procrastination at each timepoint, as well as one-time assessments of chronotype (MEQ) and circadian phase (DLMO). Non-parametric and parametric RARs were calculated from actigraphy data. Multilevel models were constructed regressing RAR metrics onto bedtime procrastination, demographic covariates, DLMO, and chronotype. Results Bedtime procrastination was associated with later activity (M10, β = 0.42, p = 0.005; up mesor, β = 0.36, p = 0.001) and rest periods (L5; β = 0.55, p < 0.001; down mesor, β = 0.48, p < 0.001 ), as well as later peak activity timing (acrophase; β = 0.43, p < 0.001) at the between-persons level. Individual differences in bedtime procrastination were also associated with poorer fit of observed RARs (pseudo R2; β = -0.27, p = 0.034). There were no significant associations between bedtime procrastination and shape (mesor, amplitude) or stability (IS, IV) indices. Associations between bedtime procrastination, L5, acrophase, and down mesor remained significant after statistically adjusting for DLMO, but associations were no longer significant after adjusting for chronotype. Conclusion Individual differences in bedtime procrastination were associated with later circadian rest-activity rhythms. Contrary to expectations, bedtime procrastination was not associated with disruptions in RAR shape or stability. Our findings suggest that there are overlapping, yet still unique, profiles of RARs associated with bedtime procrastination, circadian phase, and chronotype. Support (if any) This research was supported by the NHLBI awards 1R01HL141706-01A1 and 1F31HL176119-01.