Light is a major player in your sleep-wake patterns. It sets your circadian clock for bodily functions such as hunger, hormone secretion, alertness and sleepiness.
Managing light exposure properly is important in setting your circadian rhythm because it influences melatonin production. Known as the “hormone of darkness,” melatonin is a naturally-occurring hormone released by the pineal gland in your brain. When the sun begins to set, your brain is exposed to less light, thereby increasing melatonin production and inducing sleepiness. As the sun rises in the morning and we are exposed to light upon awakening, your melatonin production stops, and you become more alert as you spend more time in the light.
In today’s electronics-driven, 24-hour workday, always “on” society, you rely more and more on electronics to set your body clock. This can be problematic for many people. You’re biologically programmed to go to bed at night and be awake and alert during the day, with light exposure being integral in this equation.
It’s easy to forget that electricity hasn’t been around for that long in comparison to how long humans have been on the Earth. This is one of the main reasons why sleep specialists stress keeping “zeitgebers” (or external time cues) to signal wake and sleep periods. Nighttime zeitgebers typically include dimming the lights before bed and powering down (i.e. not using anything with a screen), relaxing with a book or calming music and winding down overall. Morning zeitgebers may include eating breakfast, taking a shower, exposure to bright light, and engaging in more active behaviors such as work or exercise. Keeping the timing of these zeitgebers consistent (such as a regular bedtime and wake time every day) helps keep your circadian rhythm in check.
So in essence, light exposure in the morning and during the daytime hours is important for those who desire to be asleep at night and awake during daytime hours. But what happens when someone gets up, possibly obtains little (or no) light exposure on their drive to work, and then sits in a cubicle or interior office with minimal or no natural light source?
Sunlight during the day (even on cloudy days!) is essential in maintaining alertness, good mood and overall functioning since it helps signal to our body that it is time to be awake and productive. A recent study by Cheung and colleagues in the journal Sleep* looked at the relationship between workplace daylight exposure and worker’s sleep, quality of life and activity levels. The authors found that workers with windows (compared to those without) received 173 percent more daytime light exposure, slept 46 minutes more at night, and were more likely to be physically active and report better overall quality of life.
In short, exposure to sunlight during the daytime improves nighttime sleep, daytime alertness and functioning. If you’re unable to change your office to one with more light exposure, consider taking quick walk breaks by windows, eating lunch in front of a window (or even outside!) and increasing pockets of sunlight exposure whenever you can. You’ll sleep better at night for it!
*Cheung IN, Reid KJ, Want C et al. (2013). SLEEP, Volume 36, Abstract Supplement, p. A422.
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