Impacts of Static Lighting in Confined Spaces on the Circadian Parameters, Alertness, Performance and Well-Being

Abstract

The static lighting condition (SLC) in confined spaces may pose great challenges to the health of long-stay workers, inducing sleep disorders, cognitive decline, and negative emotions such as depression or anxiety. To explore human responses to the SLC (300 lx and 6000 K), 20 young subjects (22.6 ± 1.88 years old) were recruited in the underground confined lab for a week by measuring melatonin, core body temperature (CBT), subjective alertness (KSS score), sleep quality (Pittsburgh Sleep Quality Index, PSQI), Psychomotor Vigilance Task (PVT), Hamilton Depression Scale (HAMD) and Self-rating Anxiety Scale (SAS). The results showed a posterior shift in circadian rhythm after 1 week of confinement, with 0.62 h delay of dim light melatonin onset (DLMO), higher melatonin concentrations in the evening, lower melatonin concentrations at midnight, a day-by-day increase in KSS and CBT at bedtime, but this decreased daily when waking up, with cumulative effects. There was a progressive increase in sleep latency, PSQI scores, response time and scores of subjective emotion scales, meaning worse sleep, performance and emotional state. Due to limited exposure to high-lighting stimuli during the daytime, the initial concentrations of melatonin increased in the evening and decreased before sleep. In confined spaces, active health interventions by dynamic lighting patterns were proposed to safeguard human health and performance.