Getting more light in the day and less at night is good for your health. Here's why
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Diet, exercise and sleep are fundamental to our health, but so it our relationship to light. A massive, new study suggests light-driven disruption can take years off our lives.
Getting more light in the day and less at night is good for your health. Here's why toggle caption Mar Lei/Getty Images Diet, exercise, sleep — all are fundamental to our health, but our relationship to light doesn't get mentioned as much. Now, a massive new study suggests light-driven disruption can take years off our lives. Scientists tracked nearly 90,000 people in the U.K. who spent a week with wrist-worn activity devices equipped with light sensors. Then, they analyzed their risk of dying over the next eight years. The results were published in the Proceedings of the National Academies of Sciences. The study participants with the brightest nights had a 21% to 34% higher risk of premature death, compared to those who were mostly in the dark between midnight and dawn. Sponsor Message The opposite was true for daytime. People who enjoyed the brightest days had a 17% to 34% lower mortality risk than those who were in dim environments during the daytime. The data underscore that light represents an "emerging risk factor for poor health and longevity," says Daniel Windred, lead author of the study and a postdoctoral researcher at Flinders University in Australia. Previous large-scale studies have found similar associations between mortality and light exposure, for example using satellite data and self-reports. However, the U.K study is the first to directly measure personal lighting environments around the clock. "It's a very powerful study," says Dr. Charles Czeisler, chief of the Division of Sleep and Circadian Disorders at the Brigham and Women's Hospital and Harvard Medical School. "We're not talking about a marginal change. We're talking about huge increases in risk associated with an easily modifiable risk factor," he says. While the study can only show a correlation — not prove causality — the "dose-dependent" response to light was evident even when the researchers controlled for factors like socioeconomic advantage, income and physical…