“Instead of being afraid of light at night, we should pay more attention to the fact that we, as industrialized beings, expose ourselves to far too little light during the day.”

—Till Roenneberg, Internal Time (2012)

Roughly one in every five people in the U.S. has sleep or wakefulness disorder. The U.S. Center for Disease Control has called insufficient sleep a public health problem. Insufficient sleep takes a serious toll on health as well as productivity.

So much of the popular coverage of sleep problems focuses on one single piece of advice: eliminating exposure to blue light emitted by electronic devices before bedtime.

That’s not bad advice necessarily, but it is one tiny issue that ends up receiving way too much emphasis.

And conversely, a topic that gets no attention at all is the fact that urban dwelling knowledge workers don’t get nearly enough exposure to light during the day.

City Folk Lack Light

Till Roenneberg, whom I quoted above, studies clocks, namely internal clocks, including human circadian rhythms. In analyzing a very large data set about sleep times, wake times, and light exposure, he writes:

“It is remarkable how little time many people spend outside of buildings or some kind of vehicle. According to our survey, about half of the Central European population spends on average less than an hour outdoors on work days and less than three hours on weekends. When we correlated the time people spend outdoors with their chronotype we found a very systematic relationship that can well explain the differences in sleep-wake behavior between town and country folk.”

Town folk or city dwellers are the people who commute in cars or underground, stay in an office all day long, leave work by the same commuting method, and hardly ever see the sun. At night, their cities and towns are bathed in manmade lights. The country folk, however, spend much more time outside, and their internal body clocks are much better entrained, on average, to sleeping when it’s dark and being awake when it’s light out.

When we don’t get the adequate sunshine we need, as is the case for many urban dwellers, our bodies are less entrained to the cycle of the sun.

More Natural Light Means Higher Productivity

I ran across more interesting information about daylight recently while reading up on the effects of a well designed office environment. Organizations that acknowledge the importance of natural light and design office spaces to take advantage of it have higher worker productivity, according to Al Horr et al. (2016). The authors note that Lockheed Martin reported a 15 percent decrease in absenteeism and VeriFone reported a 47 percent increase in attendance in buildings that were designed to maximize natural light.

While it’s possible to replicate the physical properties of daylight through special lightbulbs, employees simply prefer natural light. They enjoy it more, and it psychologically makes them feel better. Plus, physiologically, in terms of how natural light influences the internal body clock, full-spectrum lamps may not have the same effect.

As for getting outdoors more, it’s important to know that sun exposure counts even when you get it when the sun’s rays aren’t very strong, like early in the morning, right before sunset, and on days when it’s overcast or cloudy. The sun doesn’t need to be especially bright for us to receive its physiological benefits. Also, you can still protect your skin with adequate clothing, shade, and sunscreen.

If you’re unable to get sufficient sleep and it’s hurting your ability to be productive, ask yourself how many hours of sunlight you get each day. If it’s low, try doubling it. Perhaps my favorite finding in Roenneberg’s book is that late-night types who get an additional two hours of sun exposure during the day were able to fall asleep an hour earlier than normal.

The Nature Effect

I’ve noticed recently a renewed interest in the positive effects of nature on our health and general wellbeing. (The pendulum of trends seems to have passed its peak point in our fascination with technology, and so it’s slowly swinging once again toward the opposite of highly technological things, things like mindfulness, meditation, the outdoors, and an obsession with shiny things that come from the earth.) If we are going to seriously measure the effects of nature, scientist must control for different variables, including exposure to sunlight. One study that gets cited quite often compare the effects of being in nature, whether sitting or walking, to the same activity in an urban setting, although when I tried to read them to find out exactly what was controlled for and how, I didn’t get beyond the abstract of the paper, which was the only part of it written in English. The rest was in Japanese.

That’s not quite true; more than half the references were in English, including one paper titled, “Visiting a forest, but not a city, increases human natural killer activity and expression of anti-cancer proteins.” The same lead author is also credited with this paper, “Forest bathing enhances human natural killer activity and expression of anti-cancer proteins,” and another similar one called, “A forest bathing trip increases human natural killer activity and expression of anti-cancer proteins in female subjects.” It’s hard to take too seriously this idea that we knock our out potential for getting cancer by taking baths in the woods.

Ask, ‘How Time Do You Spend Outdoors?’

The next time the issue of insufficient sleep comes up in casual conversation, ask people how much time they spend outdoors in natural light. It would be interesting for people to start developing even an anecdotal understanding, or at least an awareness, of this idea that we need adequate sunlight during the day to sleep well at night.

References

Al Horr, Y., Arif, M., Kaushik, A., Mazroei, A., Katafygiotou, M., & Elsarrag, E. (2016). Occupant Productivity and Office Indoor Environment Quality: A Review of the Literature. Building and Environment(105) 369-389.

Roenneberg, T. (2012). Internal Time: Chronotypes, Social Jet Lag, and Why You’re So Tired. Harvard University Press. Cambridge, Mass.

Image by Michael Fraley, CC.