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LighTimes: Natural Light at Offices Improves Sleep Quality of Workers at Night

17 Sep 2014

September 16, 2014…A new study from the University of Illinois at Urbana-Champaign and Northwester Medicine found that office workers with more sunlight exposure at the office had longer sleep duration, better sleep quality. Additionally, they had higher levels of physical activity and an overall better quality of life in terms of vitality and health compared to office workers with less natural light exposure in the workplace.

Employees with windows in their offices received 173 percent more white light exposure during work hours. They reported sleeping an average of 46 minutes more per night than employees who were not exposed to natural light at the office. Workers in offices with windows also tended to report more physical activity than those without windows.

In the study, workers without windows reported poorer scores on quality of life measures that relate to vitality and physical problems in addition to poorer outcomes in terms of overall sleep quality and sleep disturbances. The study was detailed in the Journal of Clinical Sleep Medicine in June.

“There is increasing evidence that exposure to light, during the day –particularly in the morning — is beneficial to your health via its effects on mood, alertness and metabolism,” said the study’s lead author, Phyllis Zee, M.D., a Northwestern Medicine neurologist and sleep specialist. “Workers are a group at risk because they are typically indoors often without access to natural or even artificial bright light for the entire day. The study results confirm that light [exposure] during the natural daylight hours has powerful effects on health.”

“Architects need to be aware of the importance of natural light not only in terms of their potential energy savings but also in terms of affecting occupants’ health,” said co-lead author Mohamed Boubekri, an associate professor of architecture at the University of Illinois at Urbana-Champaign.

Boubekri noted that one simple design solution could help make sure that workstations are within 20 to 25 feet of the peripheral walls containing windows. ”Daylight from side windows almost vanishes after 20 to 25 feet from the windows,” he said.

The study included 49 day-shift office workers; 27 of which were in windowless workplaces, and 22 were in workplaces with windows. Study participants filled out form reporting on their quality of life and sleep quality. The researchers evaluated the forms with the Pittsburgh Sleep Quality Index (PSQI). Actigraphy measured sleep, light exposure and activity in a representative subset of 21 participants including 10 in windowless workplaces and 11 in workplaces with windows.

Actigraphy is a device worn on the wrist that measures light exposure as well as activity and sleep and keeps a record of it. The researchers used the motion to determine activity levels while awake and to calculate sleep time. The researchers also determined luminance as a measure of light exposure during the workday.