Biologically effective lighting for more relaxed flights

Partners from research and industry are studying the principles of next-generation cabin lighting

Gradual transitions from day into night have become standard today on board of modern passenger aircraft. Bergische Universität Wuppertal, the Fraunhofer Institute for Building Physics IBP, Airbus, Diehl Aerospace and Osram joined forces in a project to study how this scenario of colors and brightness can be improved to enhance passenger well-being using new chronobiologically adapted light. The result: Chronobiologically adapted lighting based on light-emitting diodes (LED), particularly on long-distance, overnight flights, leads to a medically measurable improvement in sleep, enhances well-being and promotes higher alertness upon arrival.

The model aircraft cabin at the Diehl site in Nuremberg was equipped like a real plane for the trials. Over six days, 32 test subjects each experienced three, realistic, long-distance, overnight flights on board of the simulator.

Results of the flight tests

The use of activating LED-based lighting systems improves rest and comfort parameters for passengers on long-distance flights. Warm, white light at the beginning of an overnight flight contributes to relaxation, promotes melatonin production and a slower heart rate, and thus makes the entire flight more relaxing for passengers by ensuring better sleep. In contrast, cold, white light (high blue component) in the morning after a restful night helps passengers to be more alert upon reaching their destination by suppressing excretion of the sleep hormone melatonin. Among business people, for example, this is reported to lead to better performance at their first business meeting the morning after a flight, and among tourists to a more rested start to their holiday.

Regulating the body clock with light

Light is the primary stimulus for regulating the human body clock and can therefore influence how well we rest. During the flights, the lighting was adapted to the respective phases and times of the journey using LEDs and intelligent light management systems. In addition to light intensity, the color spectra were selected in accordance with the time of day to support the circadian rhythm. The psychological and physiological reactions of the test subjects, including tiredness, sleep quality, stress, well-being and alertness, were measured and analyzed in an aircraft for the first time using a variety of medical instruments. Self- and external assessments were conducted on the basis of questionnaires; ECG measurements were taken for each test subject to determine heart rate variability; saliva samples were collected to document levels of the sleep hormone melatonin and the stress hormone cortisol; and movement sensors were used on the test subjects.

Light as a synchronizer

Light controls key bodily functions, including the sleep/wake rhythm, body temperature and hormone production. The sleep hormone melatonin promotes sleep and the stress hormone cortisol supports alertness. When we are active outdoors, it is mainly natural light that helps to synchronize our body clock. On the contrary, if we spend too much time indoors in poor lighting, or if we travel through time zones, for example on a long-distance flight, our body clock gets off track. Intelligent lighting solutions therefore are designed to minimize jet lag in the future and help passengers to overcome it more quickly.

GLOSSARY

Circadian rhythm: A biological rhythm with a period of about 24 hours (Latin: circa = approximately; dies = day), such as the sleep/wake rhythm in humans. The most important zeitgeber or synchronizer for circadian rhythms is light (cf. Lichtwissen 19 – p. 42).

Biological effect of light on humans: Light is electromagnetic radiation in the wavelength range of 380 to 780 nanometers visible to the human eye. The human eye perceives light with three different sensory cell types, which react to different wavelengths. Apart from the cones for seeing color during the day, the rods help us to see in less intense light. However, they cannot distinguish color. A recently discovered, third sensory cell type is biologically active, controlling human circadian rhythm and wakefulness. These sensory cells react to the blue wavelength range in the region of 460 nanometers (cf. Lichtwissen 19 - p.16).