Dataset Information

Prediction Of Shiftworker Alertness, Sleep, And Circadian Phase Using A Model Of Arousal Dynamics Constrained By Shift Schedules And Light Exposure.

ABSTRACT:

Study objectives

The study aimed to, for the first time, (i) compare sleep, circadian phase, and alertness of Intensive Care Unit (ICU) nurses working rotating shifts with those predicted by a model of arousal dynamics; and (ii) investigate how different environmental constraints affect predictions and agreement with data.

Methods

The model was used to simulate individual sleep-wake cycles, urinary 6-sulphatoxymelatonin (aMT6s) profiles, subjective sleepiness on the Karolinska Sleepiness Scale (KSS), and performance on a Psychomotor Vigilance Task (PVT) of 21 ICU nurses working day, evening, and night shifts. Combinations of individual shift schedules, forced wake time before/after work and lighting, were used as inputs to the model. Predictions were compared to empirical data. Simulations with self-reported sleep as an input were performed for comparison.

Results

All input constraints produced similar prediction for KSS, with 56-60% of KSS scores predicted within ±1 on a day and 48-52% on a night shift. Accurate prediction of an individual's circadian phase required individualised light input. Combinations including light information predicted aMT6s acrophase within ±1 h of the study data for 65% and 35-47% of nurses on diurnal and nocturnal schedules. Minute-by-minute sleep-wake state overlap between the model and the data was between 81±6% and 87±5% depending on choice of input constraint.

Conclusions

The use of individualised environmental constraints in the model of arousal dynamics allowed for accurate prediction of alertness, circadian phase and sleep for more than half of the nurses. Individual differences in physiological parameters will need to be accounted for in the future to further improve predictions.

SUBMITTER: Knock SA

PROVIDER: S-EPMC8598188 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The circadian rhythm, called Process C, regulates a wide range of biological processes in humans including sleep, metabolism, body temperature, and hormone secretion. Light is the dominant synchronizer of the circadian rhythm-it has been used to regulate the circadian phase to cope with jet-lag, shift work, and sleep disorder. The homeostatic oscillation of the sleep drive is called Process S. Process C and Process S together determine the sleep-wake cycle in what is known as the two-process model. This paper addresses the regulation of both Process C and Process S by scheduling light exposure and sleep based on numerical simulations of circadian rhythm and sleep mathematical models. This is a significant step beyond the existing literature that only considers the entrainment of Process C. Regulation of the two-process model poses several unique features and challenges: 1. Process S is non-smooth, i.e., the homeostatic dynamics are different in the sleep and wake regimes; 2. Light only indirectly affects Process S through Process C; 3. Light does not affect Process C during sleep. We consider two scenarios: optimizing light intensity as the control input with spontaneous (i.e., unscheduled) sleep/wake times and jointly optimizing the light intensity and the sleep/wake times, which allows limited delayed sleep and early waking as part of the decision variables. We solve the time-optimal entrainment problem for the two-process model for both scenarios using an extension of the gradient descent algorithm to non-smooth systems. To illustrate the efficacy of our time-optimal entrainment strategies, we consider two common use cases: transmeridian travelers and shift workers. For transmeridian travelers, joint optimization of the two-process model avoids the unrealistic long wake duration when only Process C is considered. The entrainment time also decreases when both the light input and the sleep schedule are optimized compared to when only the light input is optimized. For shift workers, we show that the entrainment time is significantly shortened by optimizing the night shift working light.