Daylight increases sleep quality

Exposure to daylight in the workplace leads to increased sleep quality and duration.

Think of your ideal workspace. Do you prefer fluorescent lights flickering overhead, or daylight streaming in through wide windows?

If you need help deciding, consider new findings that suggest a strong link between windows in the workplace and workers' sleep, vitality, and quality of life.

In preliminary research presented this week at the SLEEP 2013 conference in Baltimore, a team led by doctoral candidate Ivy Cheung of Northwestern University found that those who had windows in the workplace slept an average of 47 more minutes per night compared to workers in offices without daylight exposure.

They also had 173 percent more white light exposure during the workday, were more physically active, and reported better sleep quality and efficiency.

"The extent to which daylight exposure impacts office workers is remarkable," said Cheung.

Cheung's study included 49 day-shift office workers, 27 of whom worked in a windowless workplace and 22 of whom worked with windows.

The participants answered the Short-Form Health Survey (SF-36) and the Pittsburgh Sleep Quality Index (PSQI), self-report questionnaires that assess their general quality of life and sleep quality, respectively.

In a subset of 21 participants, including 10 windowless workers and 11 workers with windows, researchers measured light exposure, activity, and sleep-wake patterns with actigraphy, a monitoring technique in which wrist monitors record motor activity and other sleep-related factors like light and temperature.

The workers without windows in the workplace had worse quality of life measures related to vitality and physical problems, and poorer scores on measures of overall sleep quality, sleep efficiency, sleep disturbances, and daytime dysfunction on the PSQI. No significant actigraphy results were reported.

The researchers suggest that architects and employers should take natural daylight exposure and light levels into account when considering the structural forces that motivate office workers and encourage overall health.

"Enhanced indoor lighting for those with insufficient daylight in current offices as well as increased emphasis on sufficient daylight exposure in the architectural design of future office environments may improve office workers' physical and mental well-being," they conclude.

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