SIEMENS

When Andreas Wojtysiak turns on the bathroom light in the morning in his apartment near Munich, he's bathed in bright blue-tinted light shining down from the ceiling. When brushing his teeth at night, though, Wojtysiak, who holds a doctorate in biology and is a lighting expert at Osram, Siemens' lighting subsidiary, prefers softer light with a lot of red in it. “Light is like an external timer that reinforces the natural 24-hour rhythm of our internal clocks,” Wojtysiak explains. Light influences body functions, including sleep cycles, body temperature, and hormone production. And the kind of light that is most conducive to health and well-being is the natural light spectrum that humans have adapted to over millions of years, and which is artificially recreated in Wojtysiak's bathroom using state-of-the-art lighting technology.

A few years ago Osram became one of the world's first lamp manufacturers to offer an “activating” lamp, called Skywhite. The company also produces various lighting systems that adapt dynamically to light conditions throughout the day. Such systems are equipped with lamps that emit different light spectrums. They mainly use light-emitting diodes (LEDs), as well as halogen and energy-saving lamps. An electronic control unit combines the output of these units in a manner that causes the system to alter the light spectrum in line with the time of day. Such solutions are especially in demand where people need to concentrate, as  in schools, colleges, and office buildings. They can thus be found in a conference room at the University of Madrid and in Osram plants in Augsburg and Eichstätt, Germany. “Our systems are also being tested in hospitals and hotels, and initial results have been very promising,” says Wojtysiak. Even NASA and the European Space Agency are testing the systems.

Osram has also developed a lighting system for examination and treatment rooms in doctors' offices and hospitals. “Healthcare Lighting” allows patients to select a lighting color they find pleasant, as well as an illuminated scene, like a vacation landscape, that will distract their attention from an examination. Osram LED lamps are also used to enliven or tone down the ambience in relaxation cabins at airports, which are equipped with an upholstered bench, a table, and Internet access, and can be rented while you wait for your plane.

Blue for Breakfast. One color is particularly responsible for the biological effect of light on the human nervous system: blue. “Blue has as an effect similar to that of your morning coffee,” Wojtysiak explains. In fact, scientists have found that the color blue stimulates a tiny cell system deep within the brain called the suprachiasmatic nucleus. This system functions as the body's clock, sending out signals that regulate our day-night rhythm. Knowledge of this process is relatively new, as the light receptors responsible for its functioning were discovered only about ten years ago. Located in the retina, the receptors are mounted like rods and cones and contain melanopsin, a pigment that reacts only to blue light. Rather than enabling vision, this light sensor is only responsible for biological reactions.

Since this discovery was made, scientists at Osram—Wojtysiak, physicist Dieter Lang, and engineer Alfred Wacker—have been working on using light to activate photoreceptors in order to influence human circadian rhythms. The principle behind this idea is simple. Light with a significant blue component should be used in the mornings and early afternoon to enhance awareness and performance. Then, as evening approaches, light should be dimmed and include warmer colors to ensure a smooth transition from the concentration to the relaxation mode. In this manner, the researchers hope to be able to prevent sleeping disorders, chronic fatigue, and even depression.

Older people can benefit the most from this, as vision not only becomes more blurred with age but also more yellowed—and yellow pigments absorb the blue spectrum of light. “Older people also tend to stay indoors and are thus not exposed to much natural light,” says Lang. In other words, seniors often have to function without an external timer. For the past few years, Osram has therefore been participating in a field study that examines the effect of dynamic daylight systems on a group of residents in a senior citizens' home in Vienna, Austria. Here, white ceiling light with a high proportion of blue is used during the day—with successful results. “Most residents are now more active during the day and sleep better at night,” Lang reports.

The field study builds on earlier work. For instance, fifteen years ago, researchers demonstrated for the first time that sleeping disorders and the night time disorientation of Alzheimer's patients could be alleviated with particularly high doses of light during the day. Such exposure also reduced the incidence of depression. These findings were recently confirmed by a major study in the Netherlands. “That's one reason why lighting systems in retirement and nursing homes are now the focus of growing interest,” says Dr. Dieter Kunz, head of the Chronobiology task group at the Institute of Physiology at the Charité Hospital in Berlin.

Kunz, who also works closely with the Osram researchers, explains how bright light during the day can help people to sleep better at night. “This system oscillates like a pendulum, so if it swings more sharply to one side, it will do the same on the other. Therefore, the more awake you are during the day, the better you sleep at night.” The exact details of the mechanism behind this phenomenon are still unclear. “The effect we see as the indirect influence of optimal lighting on night sleep patterns appears to be stronger than that of most sleeping pills,” says Kunz.

However, in order to achieve the best possible effect, you not only have to coordinate light color and brightness, but also lamp types and positions. “Bluish daytime lighting should come from above and be as widespread as possible,” Wojtysiak explains. That's because the receptors in the retina are oriented toward the heavens—after all, that's where the blue sky is. On the other hand, spotlights are all that's needed for the low blue, relaxing light at night. As with any lighting system plan, designers also have to incorporate window locations and wall colors into their concept. Organic light-emitting diodes (OLEDs), which seem predestined for use as area lamps to create artificial skies, may be employed here in the future. “We're still a long way from that because the lights still have to cover larger areas and the technology needs to become more affordable,” says Wojtysiak. He believes that a combination of OLEDs for a more or less diffuse basic area lighting effect, and LEDs for direct lighting, could be an option.