Retinal light exposure is modulated by our behavior, and light exposure patterns show strong variations within and between persons. Yet, most laboratory studies investigated influences of constant lighting settings on human daytime functioning and sleep. In this presentation, I will discuss a series of studies investigating light-induced moderations in sleepiness, vitality and sleep, with a strong focus on the temporal dynamics in these effects, and the bi-directional relation between persons' light profiles and their behavior.

Laboratory studies have shown that meaningful changes in light exposure lead to phase shifts in melatonin rhythm. In natural settings, however, light is a very complex signal. How melatonin responds to weekly- and seasonal-dependent variations in light exposure is still poorly understood. In this talk I will present results from a series of observational and intervention studies on the relationship between melatonin and light exposure in the field.

What happens to human sleep and circadian rhythms in space? There are many challenges that affect sleep in space, including unusual patterns of light exposure and the influence of microgravity. This talk will review the causes and consequences of sleep loss and circadian misalignment during spaceflight and will discuss how missions to the Moon and Mars will be different than missions to the International Space Station.