Employees who are exposed to natural light at their workplace are associated with longer sleep duration, enhanced sleep quality, more physical activity and better quality of life as compared to those exposed to less light, according to a new study from the Northwestern Medicine and the University of Illinois at Urbana-Champaign.

The researchers said that the study highlights the importance of natural light exposure on employee's health. Plus, there is also the need for architectural designs of office environments to focus more on natural daylight exposure to potentially lower energy costs and improve occupants' health.

For the study, the researchers surveyed 49 day-shift office workers - 27 in window-less workplaces and 22 in workplaces with windows - for quality of life and sleep quality using the Pittsburgh Sleep Quality Index (PSQI). Light exposure, activity and sleep were measured by actigraphy in a subset of 21 participants; 10 in window-less workplaces and 11 in workplaces with windows.

The researchers found that office workers with close proximity to windows were exposed to 173 percent more white light during work hours and slept an average of 46 minutes more per night as compared to those who were not. Workers with windows were also involved in more physical activity than those without windows.

Workers without windows fared poorly on quality of life measures related to physical problems, vitality, overall sleep quality and sleep disturbances.

"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 senior study author Phyllis Zee, a Northwestern Medicine neurologist and sleep specialist, in a press release.

Zee said that workers were at a significant risk as they are often typically indoors without access to natural or even artificial bright light for the entire day.

Mohamed Boubekri, an associate professor of architecture at the University of Illinois at Urbana-Champaign, said that a simple design solution to amplify daylight penetration in office buildings would be to construct workstations within 20 to 25 feet of the peripheral walls containing the windows.

"Daylight from side windows almost vanishes after 20 to 25 feet from the windows," Boubekri said.

"Light is the most important synchronizing agent for the brain and body," said Ivy Cheung, co-lead author and Ph.D. candidate in neuroscience at Northwestern. "Proper synchronization of your internal biological rhythms with the earth's daily rotation has been shown to be essential for health."

The finding is published in the Journal of Clinical Sleep Medicine.