Imprimir Republish


The colors of the night

Red lights may be healthier than blue ones

luz1When you have to stay awake at night, leave a red light on nearby. “This might be a way of remaining alert”, states Mariana Figueiro, an architect who graduated in Belo Horizonte and who coordinates the program of research into light and health at the Lighting Research Center. Part of the Rensselaer Polytechnic Institute, in Troy, to the north of New York, this institute does basic and applied research on the impact of artificial lighting on people. In a study published in the journal BMC Neuroscience, Mariana and her team showed that red lights may be more suitable at night than the bluish ones. The researchers conducted their tests with pure-color lights to find out what are the real effects of the common white lights that tend toward blue, such as the light of white fluorescent bulbs.

“A red light helps to maintain or enhance the level of mental activity without suppressing the production of melatonin, the sleep-regulating hormone, contrary to a blue light”, says Mariana. Other studies had already shown that bluish lights may reduce the production of melatonin, released by the pineal gland at the base of the brain. Melatonin helps to regulate the circadian rhythm, i.e., the variations of phenomena such as the heartbeat frequency and sleep, which oscillate over periods of roughly 24 hours. More blue light and less melatonin might make the body more prone to the development of tumors, besides disrupting sleep. According to Mariana, those who must stay awake working at night may feel a bit sleepier with a red light, but their body will probably suffer less.

The advantages of red lights over blue ones emerged from an experiment with 14 people, who were submitted to medium and low doses of the two types of radiation for two nights. To assess the organism”s reactions precisely, Mariana”s team monitored heartbeat rates and brain activity. “A blue light is more powerful when it comes to interfering with circadian rhythms”, she concludes. Prior studies of this group had attested to the human body”s sensitivity to blue light: even an amount of blue light far lower than that of normal lighting can interfere with sleep. In another article published this year in Journal of Carcinogenis, Mariana, Mark Rea and John Bullough, from the Lighting Research Center, presented the hypothesis that environmental lighting, normally excessive to the point of interfering in the production of melanin, might be helping to increase the incidence of breast cancer. To date, however, lack of quantitative evidence makes it impossible to reach any conclusion.

The immediate implications of these results, however, are that they point to a basic research path, including the identification of healthier red and blue light combinations, among other possibilities. They also point to applications, especially regarding people who work at night, or in dim environments. One of the immediate challenges that Mariana and her team face is how to use the conclusions of these scientific experiments to improve the lighting in submarines, at the request of the US Navy. The researchers had already found that the work hours were one of the problems, with 18-hour shifts and 6 hours of rest, along with working in dimness, “as if one were in a cave”, she says. “They lose track of when it”s night or day”. The consequences for one”s circadian rhythm can be dramatic, as it demands stronger lighting to be activated. Thus, the sleep timetable can easily lose its regularity.

Mariana, along with her team, is now planning to find out what is the best strength and amount of red light to use at night and to combine with blue light during the day, not only in submarines but also in other work environments. “Blue light is better for daytime, but it might not be the best option to use at night”, she says. Her group and others from the Lighting Research Center feel at ease to face the challenge of transforming scientific discoveries into day-to-day products. They have already developed a device for personal use, the Daysimeter, which is reminiscent of a microphone and that is placed near the eyes to measure the amount of light a person gets, indicating, for instance, whether the individual”s sleep timetable should be adjusted. At present, they are working toward discovering what are the best types of light for the elderly, to help them to sleep better and avoid falls. Another project is to develop car lights that hurt the eyes less at night while also providing better lighting, of course.

Scientific article
FIGUEIRO, M. G. et al. Preliminary evidence that both blue and red light can induce alertness at nightBMC Neuroscience. V. 10. p. 105-16. 2009.