The Effects of a Blue Monochromatic Light Intervention on Evening-type Individuals' Sleep and Circadian Rhythms

The present project is aimed to contribute with new knowledge concerning how light conditions in the physical environment can be manipulated to alter the sleep and circadian rhythms of individuals with an evening-type circadian rhythm. More precisely, the study will explore whether exposure to blue light (compared to a full spectrum light control condition) during the morning hours advance the circadian rhythms of evening-type individuals, towards that which is more similar to the daily rhythm of morning-type individuals. This study is important as it has been found that evening-type adolescents and adults are at higher risk of poor academic performance and demonstrate lower intellectual performance when tested at their nonoptimal early times of day, and given the fact that most schools and workplaces structure their working hours during such early hours of the day. Such an intervention could thus help evening-type individuals better adjust to the different early day requirements that they are exposed to. The project involves a three-day intervention where participants will be exposed to blue monochromatic light, administered through ceiling mounted light emitting diode (LED)-based room lighting, in the early hours of each morning for a duration of 60 min. The participants' sleep, circadian rhythm and waking function will be assessed both objectively and subjectively. The effects of the intervention are transferable to real life educational and work settings and can thus be applied in naturalistic settings. The intervention is based on the new laboratory infrastructure available at the sleep laboratory situated in Christies gate 12.