Reprint – Electric Lights Alter Daily Rhythms

Circadian_Cycle

Photo credit: Dana Le via Flickr http://bit.ly/14zepJ9

I wrote an article entitled I Love Nightshift awhile ago. It is true, and now I know why I felt so healthy working on the lighthouse – lack of electric lights! It may not be for all people, but it did work for me. Working the night shift was done mostly in the dark as we had to watch for fog, visibility markers, lights from ships, flares, sea conditions, clouds – all only visible in the dark without electric lights.

The title and text for this article are from the.scientist.com website.

Electric Lights Alter Daily Rhythms

Humans’ circadian clocks become skewed when they are exposed to electric lights but revert to a schedule more in tune with the sun when they go camping.

By Kate Yandell | August 6, 2013

Long-term exposure to electric lighting has fundamentally altered humans’ circadian rhythms, according to a study published in Current Biology last week (August 1). But a week camping away from electric lights swiftly reset eight study participants’ circadian clocks.

“What’s remarkable is how, when we’re exposed to natural sunlight, our clocks perfectly become in sync in less than a week to the solar day,” coauthor Kenneth Wright, a University of Colorado Boulder integrative physiologist, said in a press release. Read more . . .

First seen in a Facebook article, and later in LiveScience.

 [private] For the first week of the study, participants went about their ordinary routines at home. Next, they all went camping in the Rocky Mountains for a week without flashlights or electronics.

Throughout the study, the participants wore wrist monitors that logged light intensity, time of day, and activity. At the end of each week, the researchers measured the participants’ melatonin levels, which indicate circadian cycle status.

While going about their ordinary routine, the participants went to sleep at 12:30 a.m. on average, experiencing on onset of melatonin about 2 hours prior. In the wilderness, the participants’ circadian clocks were advanced by 2 hours; they experienced an earlier onset of melatonin, coinciding with sunset, and went to sleep sooner.

The experiment also showed that a week in the wilderness reduced the differences among the participants’ daily rhythms, with the schedules of early birds and night owls converging.[/private]

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By Cari Nierenberg, Contributing writer   |   August 01, 2013 12:00pm ET
 
 
A tent is staked at the edge of a mountain lake.
Going camping for a week can reset your internal daily rhythms, a new study shows.
Credit: Camping photo via Shutterstock

A weeklong camping trip can help reset a person’s internal biological clock, so that it will be easier to wake up in the morning and feel more alert, a new study suggests.

After study participants spent more time exposed to natural light and less time in artificial lighting, researchers found their bedtimes and wake-up times shifted, both moving up to two hours earlier. 

“After camping, the night owls in the group showed the greatest shifts in the timing of their internal clocks,” said study researcher Kenneth P. Wright, Jr., an associate professor of physiology at the University of Colorado at Boulder.

“Night owls looked more similar to earlier morning types,” Wright said. In other words, night owls started keeping an early-to-bed, early-to-rise schedule, and they said they felt more alert in the morning.

This study was the first to quantify the impact of our modern lifestyle — of spending more time indoors in artificial light and less time outdoors in natural light — on human’s internal biological clocks, or circadian rhythms, the researchers said.

The findings are published online today (Aug. 1) in the journal Current Biology.

Increasing natural light

In the study, researchers looked at eight adults with an average age of 30 who did not have any sleep problems. Participants spent one week living their usual schedules of working, attending school, socializing, exercising, sleeping and waking, and they wore a wristwatchlike device that measured their light exposure. [Best Camping Spots in America’s Backyard]

Then they spent a week camping in Colorado’s Rocky Mountains in July. In the great outdoors, participants were exposed to sunlight and a campfire’s glow, but were not allowed to use any artificial light — meaning no computers, flashlights or cellphones.

Before the camping trip and after it ended, researchers measured levels of melatonin, a hormone that regulates sleep and wakefulness, as a marker for each participant’s individual biological clock. 

During the week of camping, the participants were exposed to four times more natural light, on average, compared with when they lived their normal lives, Wright said.

More natural light caused the participants’ internal clocks to become perfectly in sync with nature’s light and dark cycle, or the timing of sunrise and sunset, he pointed out.

“If people want to be more alert in the morning, they need to increase their exposure to natural lighting during the day, and decrease their exposure to electrical lighting in the evening,” Wright said.

But you don’t have to pitch a tent, unroll a sleeping bag and go camping to reap these benefits.

Wright suggested making an effort to get more natural light in the morning or at lunch by taking a walk and raising shades or blinds at home and at work. He also recommended dimming lights and reducing the intensity of artificial lights on computers, TVs, and other electronic devices an hour before bedtime.

“A flip of a light switch can be pretty powerful,” Wright said, adding that “light can be very arousing and alerting to the brain.”

Resetting internal clocks

“This study goes a considerable way toward showing the practical impact of light exposure on human biological clocks in the real world,” said Dr. Andrew Lim, a sleep neurologist at Sunnybrook Health Sciences Centre in Toronto, who was not involved in the research.

Lim said the findings reveal how an artificial lighting environment — with insufficient light during the day and excessive light after sunset — can play an important role in causing people to fall asleep later and wake-up later. It leads to a misalignment between sleep-wake cycles and an individual’s internal biological clock.

Lim said that it’s difficult to attribute all of the observed effects in the study to differences in light exposure alone, because campers also had different activity levels and social schedules than they would at home.

He also mentioned that it’s unclear whether these results would hold true in other latitudes, during other seasons besides summer, and in different age groups. 

Editor’s Recommendations

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Joel N. Shurkin, ISNS Contributor   |   August 01, 2013 03:15pm ET
 
 
camping resets internal clock
Credit: FLorian via flickr | http://bit.ly/1bOnDE0

(ISNS) — Throughout most of human history, humans went to bed shortly after the sun went down and woke up in the morning as it rose. There were candles and later oil lamps, but the light was not very bright so people still went to bed early.

Then came Thomas Edison and the incandescent light bulb and everything changed, including our sleeping habits. So, if you have problems getting to sleep at night or are a miserable person to be around in the morning, blame him.

Scientists at the University of Colorado Boulder found that if you live by the sun’s schedule, you are more likely to go to bed at least an hour earlier, wake up an hour earlier, and be less groggy, because your internal clock and external reality are more in sync. The sun adjusts your clock to what may be its natural state, undoing the influence of light bulbs. 

The work is published in the current issue of the journal Current Biology.

The disconnect between the outside environment and sleep is one reason why even native Alaskans have problems sleeping in the almost endless days of the Arctic summers, and get depressed during the long nights of winters.

The subjects in the Colorado study lived more normal lives.

“We weren’t studying people who had sleep difficulties,” said Kenneth Wright, an integrative psychologist at Boulder. “The amount of sleep they got did not change. What changed was the timing of their sleep and the timing of their [internal] clock relative to when they slept.”

The researchers took eight adults, average age around 30, and followed them around the normal course of their lives for a week. The subjects spent most of their time indoors while working, studying, eating, and sleeping. Most of the light they encountered was artificial. Then, they sent the same people out camping.

Sleep and light were measured daily and the hormone melatonin every hour across 24 hours, once after the week of living at home, going to work, school, and then after a week of camping.

Melatonin is the “hormone of darkness,” said Namni Goel, a psychologist and sleep researcher at the University of Pennsylvania in Philadelphia. Scientists use the hormone to measure photoperiods, or the physiological response that organisms have to cycles of daylight and darkness. 

“It rises at night naturally, and falls during the day, suppressed by light,” said Goel.

Melatonin also drops the body’s core temperature, making it easier to sleep. People often take melatonin pills to help them fall asleep, she said.

After the week’s study indoors, the Colorado subjects went camping in the Rockies. Instead of artificial lighting, they had only sunshine during the day and campfires at night. Wright estimates the light from the sun was four times as intense as what they experienced indoors. The nature of the light also changed during the day. Think of the bright white light of midday and the golden glow that often precedes sunset.

After their week of camping, researchers measured the subjects’ melatonin levels again.

The researchers found that the onset of melatonin shifted two hours earlier, and the subjects’ actual sleep shifted more than an hour earlier. Their bodies were recalibrating themselves, Wright explained.

When they woke in the morning in their normal lives, the melatonin and the external time were in conflict. They were waking up, but the melatonin in their bodies was telling them they should still be asleep. That might account for their still feeling sleepy, Wright said.

When they were out in the outdoors, the melatonin levels and the sun cycle were more aligned–the levels went down as the sun rose and before they woke up. They were subject to more light — sunlight — for the majority of the day.

The relationship between light and sleep and how much sleep a person needs has been the subject of several classic experiments.

Some involving putting subjects in deep, totally dark caves for weeks at a time have discovered that the 24-hour-day is almost exactly right for our bodies. The average amount of time our bodies consider a day comes to 24.3 hours, Goel said.

Goel and other Colorado scientists agree that the experiment was small, with only eight subjects, which limits what can be concluded. Nonetheless, the findings justify more experiments like it.

And more camping.

Inside Science News Service is supported by the American Institute of Physics. Joel Shurkin is a freelance writer based in Baltimore. He is the author of nine books on science and the history of science, and has taught science journalism at Stanford University, UC Santa Cruz and the University of Alaska Fairbanks. [/private]

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