Northwestern Medicine and the University of Illinois at Urbana-Champaign found that office workers with more light exposure at the office had longer sleep duration, better sleep quality, more physical activity and better quality of life compared to office workers with less light exposure in the workplace.
Employees with windows in the workplace received 173 percent more white light exposure during work hours and slept an average of 46 minutes more per night than employees who did not have the natural light exposure in the workplace. There also was a trend for workers in offices with windows to have more physical activity than those without windows.
Workers without windows reported poorer scores than their counterparts on quality of life measures related to physical problems and vitality, as well as poorer outcomes on measures of overall sleep quality and sleep disturbances.
The study group included 49 day-shift office workers; 27 in windowless workplaces and 22 in workplaces with windows. Health-related quality of life and sleep quality were measured with a self-reported form and sleep quality was evaluated with the Pittsburgh Sleep Quality Index (PSQI). Light exposure, activity and sleep were measured by actigraphy in a representative subset of 21 participants; 10 in windowless workplaces and 11 in workplaces with windows.
Actigraphy is a single device worn on the wrist that gives measures of light exposure as well as activity and sleep. This is an ambulatory physiological data logger that records motion and light illuminance. The motion was used to determine activity levels during waking time and to calculate sleep time. The light luminance was used for measures of light exposure during the workday period.
The study is published in the Journal of Clinical Sleep Medicine.