The Impact of Lighting Conditions on Users' Alertness and Working Memory in Confined Spaces.

Confined spaces, characterized by limited natural ventilation, the absence of windows, and restricted access to natural light, present distinct challenges. While most studies focus on lighting's effect on sleep, confined spaces are now more often used for short-term work-rest cycles, especially in office settings. This study explores how lighting conditions affect alertness, cognitive performance, and physiological metrics such as heart rate variability (HRV) during work-rest cycles in confined spaces. Participants performed 2-back tasks, psychomotor vigilance tasks (PVT), and completed subjective scales under six lighting conditions, combining two levels of illuminance (300, 500 lx) and three color temperatures (2800, 5000, 6500 K). Results show higher subjective alertness during work with 300 lx and 5000 K. However, lighting conditions did not significantly affect subjective alertness during rest. Objective alertness was better at 300 lx, with 2800 outperforming 5000 K. Working memory accuracy was higher at 5000 compared with 6500 K, and reaction times were faster under 300 lx. Physiological data remained consistent across lighting conditions. These findings can inform future lighting design and management in confined spaces to improve comfort and efficiency.