Optimising lighting conditions to enhance seafarer adaptation to the '6-h on/6-h off' shift pattern: a balanced crossover study

Chenyao Zhao; Nuoyi Li; Xiangwei Yi; Xiao Wang; Ying He; Haiping Shen; Yandan Lin

doi:10.1111/jsr.14450

Optimising lighting conditions to enhance seafarer adaptation to the '6-h on/6-h off' shift pattern: a balanced crossover study

J Sleep Res. 2025 Jan 12:e14450. doi: 10.1111/jsr.14450. Online ahead of print.

Authors

Chenyao Zhao¹, Nuoyi Li¹, Xiangwei Yi², Xiao Wang¹, Ying He³, Haiping Shen¹, Yandan Lin^{1

4}

Affiliations

¹ Department of Light Sources and Illuminating Engineering, School of Information Science and Technology, Fudan University, Shanghai, China.
² Institute of Future Lighting, Academy for Engineering and Technology, Fudan University, Shanghai, China.
³ Naval Medical Center, Naval Medical University, Shanghai, China.
⁴ Intelligent Vision and Human Factor Engineering Center, Shanghai, China.

PMID: 39801025
DOI: 10.1111/jsr.14450

Abstract

The '6-h on/6-h off' shift pattern could potentially disrupt the physiological rhythms and cognitive performance of seafarers, attributed to its shorter and more frequent shifts. Conversely, light exposure has been demonstrated to enhance cognitive abilities and synchronise physiological processes. Therefore, we studied the fatigue, cognition, sleep and rhythm of seafarers with different shifts to determine how light can benefit their performance. A total of 16 seafarers participated in a 2 × 2 crossover study, which involved two shift types (Morning-Evening and Day-Night) and two lighting conditions (static lighting and dynamic lighting). Sleepiness, cognition and fatigue were assessed every 2 h during '6-h on' period, using the Karolinska Sleepiness Scale, psychomotor vigilance task, critical flicker frequency and visual analogue scale for fatigue. Sleep was monitored during '6-h off' period, core body temperature was continuously tracked for rhythm throughout the shift protocol. For the Day-Night shift, the static mode with stable higher illuminance than dynamic lighting significantly reduced sleepiness (p = 0.01), objective fatigue (p = 0.001), subjective fatigue (fatigue level [p = 0.004] and visual fatigue [p = 0.001]) during the night period, while increasing sleep duration during the day (6:00 a.m. to 12:00 p.m.) and delaying the rhythm. For the Morning-Evening shift, dynamic lighting with lower illuminance significantly increased sleep duration during the night (12:00 a.m. to 6:00 a.m.) without causing a significant difference in performance. Overall, static lighting is more suitable for Day-Night shift seafarers due to lower sleepiness, fatigue and longer daytime sleep duration, while dynamic lighting is more suitable for Morning-Evening shift seafarers due to longer night-time sleep duration. Therefore, different lighting patterns should be adopted for seafarers during different shifts.

Keywords: cognitive performance; fatigue; lighting; rhythm; sleep; ‘6‐h on/6‐h off’ shift.

Grants and funding

23AH0801/The Science and Technology Commission of the Military