a desk near a windowThe amount of light a person is exposed to during the day can affect how he or she sleeps at night. Researchers from the Northwestern University Feinberg School of Medicine investigated how the amount of light in the workplace affects sleep quality and duration, and overall well-being. The study revealed that people whose workspaces are closer to windows get more sleep and have higher levels of physical activity than employees who work far from natural light. The results suggest that light plays a critical role in employee health.

The researchers monitored 49 day-shift office employees—27 worked in areas without windows and 22 worked in areas with windows. The employees completed a self-reported survey about their health-related quality of life. The researchers assessed the employees’ sleep quantity using the Pittsburgh Sleep Quality Index. To determine the employees’ exposure to light, a representative subset of 21 participants received actigraphy devices. The workers wore the devices on their wrists. The researchers used the devices to measure light exposure, activity levels, and sleep time.

Employees in offices with windows were better off than employees in windowless offices. In offices with windows, the employees received 173% more white light exposure during work hours. These employees slept an average for 46 minutes more per night and participated in more physical activity compared to employees in windowless offices. The employees without windows had worse scores in measurements of sleep and vitality. These employees also had lower sleep quality and more sleep disturbances.

The findings emphasize the importance of exposure to natural light during the day. According to the study, employees working within 20 to 25 feet of walls containing windows received the benefits of light exposure.

“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 … The study results confirm that light during the natural daylight hours has powerful effects on health,” stated senior study author Phyllis Zee, M.D., neurologist and sleep specialist at Northwestern Medicine.

This research is published in the Journal of Clinical Sleep Medicine.

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