Study: Natural light improves office workers' health

Lab rats already knew it. Now a new field study supports it: Working in dark, dingy offices with no natural light is not just bad for your mood. It's bad for your health.

The research by Northwestern University and the University of Illinois at Urbana-Champaign found that office workers exposed to natural light slept better, were happier, reported better health, and were more likely to be active throughout the day than their counterparts in windowless offices.

The findings indicate that positioning workers near windows is an "overlooked opportunity to improve health and fitness," said Phyllis Zee, senior author of the report, a neurologist, sleep specialist and professor of neurology with Northwestern University's Feinberg School of Medicine in Chicago.

Zee said previous studies on animals and in labs showed the importance of natural light for alertness, improving sleep, and maintaining cognitive performance.

Researchers studied 49 day-shift workers, including 27 in windowless workplaces and 22 in offices with windows. Because workers with window-lined offices tend to be higher up on the pay and power scale, the study was adjusted for those factors, Zee said.

The biggest effect of being exposed to more light was improved sleep - an average of an additional 46 minutes per night.

Other studies have found that people who are exposed to morning light have a lower body mass index, she said.

"Morning light tends to decrease appetite, while evening light will have the opposite effect. So you want light in the morning and during the day, and decreased exposure in the evening."

One unexpected finding was that workers bathed in natural light were more likely to be more physically active throughout the day, Zee said. "We don't understand the mechanisms, but if you want to stay more active, it makes you think light may be playing an important role."

To get the benefits of natural light, workstations should be within 20 to 25 feet of a window, since daylight "almost vanishes" at greater distances, according to the study.

Zee said other studies show that certain enhanced artificial lighting - high-intensity lights enriched with blue light, for example - could have some benefits, as well, without the damaging effects of ultraviolet radiation in sunlight.

She said workers should focus on ways to increase light exposure outside the workplace, such as walking longer distances to work from the bus or parking lot, and eating outdoors or at a lunchroom or restaurant with natural light.