0167 Determinants Of Irregular Sleep On Different Work Schedules Using Mathematical Modeling. (27th April 2018)

• Record Type: Journal Article
• Authors: Fischer, D; Klerman, E B; Phillips, A J
• Is Part Of: Sleep. Volume 41(2018)Supplement 1
• Page Start: A65
• Page End: A65
• Publication Date: 2018-04-27
• Subjects: Sleep -- Physiological aspects -- Periodicals; Sleep disorders -- Periodicals; Sommeil -- Aspect physiologique -- Périodiques; Sommeil, Troubles du -- Périodiques; Sleep disorders; Sleep -- Physiological aspects; Sleep -- physiological aspects; Sleep Wake Disorders; Psychophysiology; Electronic journals; Periodicals; 616.8498
• DOI: 10.1093/sleep/zsy061.166
• Languages: English
• ISSNs: 0161-8105

Abstract

Abstract: Introduction: Even on the same work schedule (regular or rotating), two individuals can differ in the regularity of their sleep patterns. Recent studies have reported a relationship between low day-to-day sleep regularity and a late circadian phase or late chronotype based on two novel metrics: Sleep Regularity Index (SRI) and Composite Phase Deviation (CPD). We aimed to identify possible mechanisms that underlie this relationship using a validated mathematical model of human sleep-wake regulation. Methods: Sleep-wake patterns were generated under realistic constraints on sleep timing for a range of circadian periods from short (τ = 23.8 h) to long (τ = 24.4 h). We simulated schedules of weekly daytime work and rotating shift-work by enforcing wakefulness during work times ± commute time. Light exposure was set to 800 lux during the day, 40 lux in the evening, and 0 lux during sleep. Sleep regularity was assessed by calculating two metrics: SRI (similarity of sleep-wake patterns between consecutive 24-h time intervals) and CPD (difference in midsleep timing between consecutive days and relative to chronotype). Work start times and intrinsic circadian period τ were varied to investigate the impact of exogenous vs. endogenous model factors on SRI and CPD. Results: Longer τ-values resulted in later chronotypes independent of work schedule type and start times. Sleep regularity was lower (lower SRI, higher CPD) in most scenarios for longer τ-values and later chronotypes, particularly in the day-work schedule for early start times (before 7:00). It was possible to reverse this relationship (i.e., lower regularity for shorter τ-values and earlier chronotypes) in the rotational shift schedule by advancing shift times; such a schedule forces the earliest chronotypes to be awake at times when the latest chronotypes had to be awake at under standard shift times. Conclusion: Our findings suggest that irregular sleep patterns are the result of the interaction between external, environmental characteristics (i.e., imposed work schedules, self-selected light exposure) and individual, endogenous traits (i.e., circadian period), and are not only a characteristic of late chronotypes. Support (If Any): R00HL119618, K24HL105664, R01HL114088, R01GM105018, R01HL128538, P01AG009975.