Long-Term Effects of Dynamic Lighting on Sleep, Circadian Rhythms, and Alertness of Individuals in Confined Spaces

Abstract:

Individuals who spend long periods of time in confined spaces that lack light are prone to problems such as circadian rhythm disruption and sleep disorders. This paper investigates the impact of lighting on 20 subjects in an underground confined space over 4 consecutive weeks， with different lighting pattern applied each week. Melatonin， cortisol， subjective sleepiness， and core body temperature are measured at bedtime， while metrics such as subjective sleep scores， sleep onset latency， nocturnal reaction time， and error rate are monitored. The results show that a daily decrease in melatonin concentration and sleepiness at bedtime and a daily increase in core body temperature under the constant lighting pattern in the 1st week. In the 2nd week， the routine is advanced by 2 hours. In the 3rd week， a dynamic lighting pattern with bright light stimulation at night led to an increase in core body temperature and cortisol concentration at bedtime， a decrease in melatonin concentration and subjective sleepiness， as well as a daily increase in sleep scores and sleep latency. Additionally， sleep quality deteriorated daily， with shorter reaction times and lower error rates. In the 4th week， a dynamic lighting pattern of strong lighting stimulation in the morning and dim light protection at night resulted in a significant increase in melatonin concentration and sleepiness at bedtime， as well as a day-by-day decrease in core body temperature and sleep latency. Sleep quality gradually improved over the week. These findings suggest that the effects of lighting on circadian rhythms and sleep quality cumulate over time. Dynamic lighting patterns can be strategically used to help people in the confined spaces maintain stable circadian rhythms and adapt to respective shift work schedules.

Key words:architecture lighting;confined spaces;healthy lighting;circadian rhythm;sleep quality