August 2, 2013
A Week Spent Camping Can Help Reset Your Circadian Clock
April Flowers for redOrbit.com - Your Universe Online
According to a recently published study, the circadian clocks of eight people were successfully synched with the timing of sunrise and sunset by doing nothing more than spending one week exposed only to natural light while camping in the Rocky Mountains.
"What's remarkable is how, when we're exposed to natural sunlight, our clocks perfectly become in synch in less than a week to the solar day," said CU-Boulder integrative physiology Professor Kenneth Wright.
Electrical light became widely available in the 1930s. This ability to flip a switch and flood a room with light has allowed humans to be exposed to light much later into the night than would be possible naturally. Our circadian clocks, which tell our bodies when to prepare for sleep and when to prepare for wakefulness, have been affected by this phenomenon.
Even during daylight hours, the intensity of indoor electrical lighting is much less than sunlight, and the color of electrical lights differs from natural light, which changes shade throughout the day.
Wright, who also is the director of CU-Boulder's Sleep and Chronobiology Laboratory, led the research team as they quantified the effects of electrical lighting. The team monitored eight participants - six men and two women with a mean age of 30 - for one week as they went about their daily lives, wearing a wrist monitor that recorded the intensity of light they were exposed to. It also recorded the timing of that light, and the person's activity. This allowed the researchers to infer when the participant was sleeping. The participants followed their normal routine of work, school, social activities, and self-selected sleeping schedules with the normal exposure to electrical lighting.
The researchers recorded the participants' circadian clock timing at the end of the week by measuring the presence of the hormone melatonin. Our bodies signal the onset of our biological nighttime with the release of melatonin. These hormone levels decrease again at the start of our biological daytime.
The team recorded the same metrics during and after a second week, during which the participants went camping in Colorado's Eagles Nest Wilderness. During the week of camping, the subjects were exposed only to sunlight and the glow of a campfire. They were not allowed access to flashlights or personal electronic devices.
When they were exposed to electrical lighting, the participants' biological nighttime started about two hours later, on average, than after a week of camping. During the first week of the study, when the participants went about their normal lives, the scientists found they woke up before their biological night had ended as well.
During the camping trip, the participants were exposed to approximately four times the intensity of light compared with their normal lives. After the trip, the team found participants' biological nighttime began near sunset and ended at sunrise. The participants also woke up just after their biological night ended. All of the participants synched with sunset and sunrise, even though measurements from the previous week indicated some people were prone to staying up late and others to getting up earlier.
"When people are living in the modern world - living in these constructed environments - we have the opportunity to have a lot of differences among individuals," Wright said. "Some people are morning types and others like to stay up later. What we found is that natural light-dark cycles provide a strong signal that reduces the differences that we see among people - night owls and early birds - dramatically."
Our propensity to become night owls or early birds when there is no strong signal to nudge our internal clocks is genetically determined.
The findings of this study demonstrate just how strong of a signal exposure to natural light is, and offer potential solutions for people who are struggling with their sleep patterns. People who are naturally night owls, for example, may also find it's more difficult to feel alert in the morning - when melatonin levels may indicate they're still in their biological nighttimes - at work or in school.
The team suggests exposure to more sunlight in the morning or midday to nudge the internal clock of a person with genetic drift towards later nights. Other suggestions include dimming electrical lights at night, forgoing late-night TV and cutting out screen time with laptops and other personal electronic devices to help reset internal circadian clocks and help the keep more closely attuned with the solar day.
"By increasing our exposure to sunlight and reducing our exposure to electrical lighting at night, we can turn our internal clock and sleep times back and likely make it easier to awaken and be alert in the morning," said Wright.