Modern life – a cycle of inadequate exposure to natural light during the day and overexposure to artificial light at night – can mess with the body’s natural sleep pattern.

But new lighting may be able to restore the body’s circadian rhythm, the biological mechanism that enables restful sleep, according to UConn Health cancer epidemiologist Richard Stevens, who has been studying the effects of artificial lighting on human health for three decades.

“It’s become clear that typical lighting is affecting our physiology,” Stevens says. “We’re learning that better lighting can reduce these physiological effects. By that we mean dimmer and longer wavelengths in the evening, and avoiding the bright blue of e-readers, tablets, and smart phones.”

Stevens and co-author Yong Zhu from Yale University explain the known short-term and suspected long-term impacts of circadian disruption in a newly published article published in the British journal Philosophical Transactions of the Royal Society B.

“It’s a new analysis and synthesis of what we know up to now on the effect of lighting on our health,” Stevens says. While short-term effects can be seen in sleep patterns, “there’s growing evidence that the long-term implications of this have ties to breast cancer, obesity, diabetes, and depression, and possibly other cancers.”

For people, electronic devices emit enough blue light when used in the evening to suppress the sleep-inducing hormone melatonin and disrupt the body’s circadian rhythm.

For all life forms – including plants, insects, and animals – excessive lighting of the night sky also has an impact that is just now beginning to be appreciated, say Stevens and Zhu. Yet newer technology is now making it possible to generate, direct, and manage light at night to better accommodate the circadian physiology of life forms in general, the researchers add.

Stevens recommends that people become aware of how the type of light emitted from electronic devices affects our biology. He says a recent study comparing people who used e-readers to those who read old-fashioned books in the evening showed a clear difference – the e-readers showed delayed melatonin onset.

“It’s about how much light you’re getting in the evening,” Stevens says. “It doesn’t mean you have to turn all the lights off at eight o’clock every night, it just means if you have a choice between an e-reader and a book, the book is less disruptive to your body clock. At night, the better, more circadian-friendly light is dimmer and, believe it or not, redder, like an incandescent bulb.”

Stevens was on the scientific panel whose work led to the classification of shift work as a “probable carcinogen” by the International Agency on Cancer Research in 2007.

Philosophical Transactions of the Royal Society B goes back to the 17th century. Its authors have included noted scientists Isaac Newton and Charles Darwin. The publisher claims it to be the world’s first scientific journal.

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