Administration of blue light in the morning and no blue-ray light in the evening improves the circadian functions of non-24-hour shift workers

ABSTRACT

In modern 24-hour society, various round-the-clock services have entailed shift work, resulting in non-24-hour schedules. However, the extent of behavioral and physiological alterations by non-24-hour schedules remains unclear, and particularly, effective interventions to restore the circadian functions of non-24-hour shift workers are rarely explored. In this study, we investigate the effects of a simulated non-24-hour military shift work schedule on daily rhythms and sleep, and establish an intervention measure to restore the circadian functions of non-24-hour shift workers. The three stages of experiments were conducted. The stage-one experiment was to establish a comprehensive evaluation index of the circadian rhythms and sleep for all 60 participants by analyzing wristwatch-recorded physiological parameters and sleep. The stage-two experiment evaluated the effects of an intervention strategy on physiological rhythms and sleep. The stage-three experiment was to examine the participants’ physiological and behavioral disturbances under the simulated non-24-hour military shift work schedule and their improvements by the optimal lighting apparatus. We found that wristwatch-recorded physiological parameters display robust rhythmicity, and the phases of systolic blood pressures and heart rates can be used as reliable estimators for the human body time. The simulated non-24-hour military shift work schedule significantly disrupts the daily rhythms of oxygen saturation levels, blood pressures, heart rates, and reduces sleep quality. Administration of blue light in the morning and no blue-ray light in the evening improves the amplitude and synchronization of daily rhythms of the non-24-hour participants. These findings demonstrate the harmful consequences of the non-24-hour shift work schedule and provide a non-invasive strategy to improve the well-being and work efficiency of the non-24-hour shift population.

KEYWORDS:

• Blue light
• circadian clock
• melatonin
• non-24-hour shift
• sleep
• light spectrum-based intervention

Acknowledgments

We wish to thank the members of the Han Wang laboratory for helpful discussions during the study and Shuangju Wu for her assistance with NanoString experiments.

Authors’ contributions

Study design: HW, QL, and ZZ. Study conduct: ZZ, XT. Data collection: ZZ, XT, XA, JL, JC, YJ, BL, QS, MZ, and YW. Data analysis: ZZ, QL, and HW. Data interpretation: HW, QL, and ZZ. Drafting manuscript: TT and ZZ. Revising manuscript content: HW, TT, and ZZ.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Consent for publication

All the authors approve the final version of the manuscript.

Data availability statement

Requests for the datasets of the current study should be directed to Han Wang ([email protected] or [email protected]).

Ethics approval and consent to participate

All research protocols were performed in accordance with the guidelines approved by the Ethics Committee of Soochow University (#SUDA20200730H03). All the participants signed written informed consent.

Supplementary data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/07420528.2024.2305218.

Additional information

Funding

This work was supported by grants from the National Key R&D Program of China [2019YFA0802400], the National Natural Science Foundation of China (NSFC) [#81701347, #31961133026, #81570171, #31871187, and #81070455], Jiangsu Province Science Foundation for Youths [BK20170351], and the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions.