Effect of blue-enhanced light on alertness and sleep-wake behaviour

If astronauts are exposed to insufficient background lighting during their missions, they could experience physiological changes, which could have a detrimental effect on mission success. This could include disturbances in their sleep/vigilance, mental and physical performance, and metabolism.

A new visual sensory system has recently been discovered in humans: a non image forming visual system which detects light irradiance. The sensitivity of this new visual system peaks in the blue range of the visible light spectrum. Visual light exposure has a wide range of effects in humans: synchronisation of circadian rhythms and sleep; suppression of melatonin, which regulates biorhythms; increase in cortisol levels, which affects metabolism; regulation of heart rate; contraction/expansion of the pupil; and changes in mood, alertness and performance.

Subjects will be stimulated over several two-week periods with blue-enriched light. An evaluation will be made of the cumulative effect of the visible light in the Mars 500 isolation chamber on sleep-wake behaviour, sleep quality, subjective alertness levels, and circadian rhythms. Individual light exposure will be measured with newly- developed environmental sensors that are worn by each subject.

Sleep duration and quality will be measured with a sleep questionnaire. Sleep-wake activity will be continuously recorded via a small, wrist worn device (an 'actimeter', the size of a small watch). Computerised tests will be used to measure participants’ alertness and mental performance, and circadian rhythms will be determined by measuring melatonin levels in saliva.

Stimulation by blue-enriched light is expected to have a positive effect on circadian rhythms. A significant positive correlation between the amount of blue light stimulation and waking alertness and sleep quality in crewmembers is also expected to be observed.

Science Team: Luzian Wolf (AT) et al.