A study from Northwestern Medicine and the University of Illinois at Urbana-Champaign indicates that all-day exposure to natural light, even by means of a window, leads to longer sleep duration at night, as well as increased physical activity and quality of life.
"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," says senior study author Phyllis Zee, M.D., a Northwestern Medicine neurologist and sleep specialist.
The study was conducted on office workers, and windows in the workplace could mean up to 173 percent more white light exposure during the day and an average of 46 minutes more sleep at night, researchers concluded.
They also noted a trend of workers with more light exposure being more physically active than their counterparts.
In the study, researchers surveyed 49 day-shift office workers, of which 27 worked in windowless offices and 22 had windows in their offices.
Quality of life and everything health-related was self-reported, whereas sleep was assessed by means of the Pittsburgh Sleep Quality Index (PSQI).
A subset of 21 participants was surveyed for light exposure, activity and sleep by means of actigraphy. Ten of these participants worked in windowless environments and 11 hailed from workplaces with windows.
Actigraphy logs ambulatory physiological data, in this case motion and light illuminance, by means of a scientific wearable device.
"Light is the most important synchronizing agent for the brain and body," says Ivy Cheung, co-lead author and Ph.D. candidate in neuroscience in Zee's lab at Northwestern. "Proper synchronization of your internal biological rhythms with the earth's daily rotation has been shown to be essential for health."
Sunlight is an important source of vitamin D and a CDC report indicates sun exposure is important even for breast-fed babies, despite the high quantities of vitamin D in breast milk.
The study was published in the Journal of Clinical Sleep Medicine.