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Exposure to Natural Light Improves Workplace Performance

Study links light exposure in the workplace to improved sleep and vitality.

Key points

  • Research shows that office workers without windows suffer in terms of overall sleep quality and sleep efficiency.
  • Light is the main cue influencing circadian rhythms that dictate sleep-wake cycles, hormone release, body temperature, and other key functions.
  • The American Academy of Sleep Medicine (AASM) considers sleep disorders an illness that has reached epidemic proportions.

We all know the discombobulated feeling of being stuck in a windowless room under fluorescent lights during daylight hours. One reason I’ve never been able to maintain a traditional 9-to-5 office job is that after a week or two of working without natural light, my mind and body begin to short circuit and I quit. I’ve never been able to make it past an entry-level position in a cubicle to enjoy the natural light of the "corner office." How does working in a windowless environment under artificial light make you feel?

Let the Sun Shine In!

Researchers at the Interdepartmental Neuroscience program at Northwestern University in Chicago reported this week that the detrimental impact of working in a windowless environment is a universal phenomenon. A new study titled, "Impact of Workplace Daylight Exposure on Sleep, Physical Activity, and Quality of Life" concludes that there is a strong relationship between workplace daylight exposure and office workers' sleep, activity, and quality of life. The research abstract was published recently in an online supplement of the journal SLEEP.

Compared to workers in offices without windows, those 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. Workers without windows reported lower scores than their counterparts on quality of life measures related to physical problems and vitality. They also had poorer outcomes in measures of overall sleep quality, sleep efficiency, sleep disturbances, and daytime dysfunction.

"The extent to which daylight exposure impacts office workers is remarkable," said study co-author Ivy Cheung, a Neuroscience doctoral candidate at Northwestern University. "Day-shift office workers' quality of life and sleep may be improved via emphasis on light exposure and lighting levels in current offices as well as in the design of future offices," said Cheung.

The study group comprised 49 day-shift office workers — 27 in windowless workplaces and 22 in workplaces with windows. Health-related quality of life was measured using the Short Form-36 (SF-36), 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.

Daylight and Circadian Rhythms

Circadian rhythms are biological, mental, and behavioral changes that follow a 24-hour cycle and respond to light and darkness within an organism’s environment. Circadian rhythms are found in almost every living thing, including human beings, animals, plants, and even tiny microbes. The study of circadian rhythms is called chronobiology.

Circadian rhythms are produced by natural factors within the body, but they are mostly affected by signals from the environment. Light is the main cue influencing circadian rhythms. Exposure to light turns the genes that control an organism’s internal clocks "on" and "off." Circadian rhythms dictate sleep-wake cycles, hormone release, body temperature, and other important bodily functions.

Disruptions of circadian rhythms are directly linked to sleep disorders. Abnormal circadian rhythms have also been associated with obesity, diabetes, depression, bipolar disorder, and seasonal affective disorder (SAD).

The “master clock” that controls circadian rhythms consists of a group of nerve cells in the brain called the suprachiasmatic nucleus, or SCN. The SCN contains about 20,000 nerve cells and is located in the hypothalamus. Destruction of the SCN results in the complete absence of a regular sleep-wake cycle.

The SCN receives information about illumination and the quality of light through the retina. The retina contains "classical" photoreceptors ("rods" and "cones"), which are used for vision. The retina also contains specialized cells which are photosensitive and project directly to the SCN where they entrain your master circadian clock to synchronize biological rhythms.

The SCN takes the information on the length of the day and night from the retina, interprets it, and passes it on to the pineal gland. In response to signals from the SCN, the pineal gland secretes the hormone melatonin. The secretion of melatonin peaks at night and ebbs during the day which drives our sleep-wake cycle.

The presence of melatonin also provides information about the length of night. Several studies have indicated that pineal melatonin feeds back on SCN rhythmicity to modulate circadian patterns of activity and other processes. However, the nature and significance of this feedback loop are unknown.

Conclusion: Sleep Disorders Are an Epidemic

Do you have trouble sleeping? The American Academy of Sleep Medicine (AASM) considers sleep disorders an illness that has reached epidemic proportions. AASM encourages patients to talk to their doctors about sleep problems. You can also visit their website for a searchable directory of sleep centers in your area if you suffer from a sleep disorder.

Ivy Cheung and her colleagues at Northwestern conclude, “The architectural design of office environments should take into consideration how natural daylight exposure may contribute to employee wellness.”

If you are currently working in a windowless environment—or suffer from seasonal affective disorder (SAD) in the wintertime—you can greatly impact the SCN and your circadian rhythms by using a lightbox that mimics outdoor light.

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