Tired? Stressed? The Cure is Camping!

Photo Credit: C.Fitzsimmons. Henry Coe State Park, CA

Spending time outside is a great way to unwind for many people. Research has shown that in addition to the physical benefits of participating in outdoor sports, there are also numerous psychological benefits, such as reduced stress, and increased ability to focus. But what about sleep?

Many people living in large, urban centers are exposed to artificial light. While nobody can deny the importance of artificial light in our society, these artificial lights can also impact the quality of sleep and disrupt internal circadian rhythms--which tell our bodies when to prepare for sleep and when to return to wakefulness. The ability to control our exposure to light has expanded the hours we work far beyond our natural internal clock. Yet exactly how much this clock has been effected was unknown. 

A recent report in Current Biology (1) aimed to address just that. The report by Wright et al. compared the effects of a normal daily, electrical-light environment to a week of exposure to only natural lighting.

In the first part of the study, they measured the light exposure and internal circadian timing of 8 participants as they went about daily routines (including school/work, social activities, and self-selected sleep schedules.) This was measured with wrist monitors that recorded the intensity of the light, and the participants activity. Following the week of "typical" light exposure, the scientists took the volunteers on a week-long backpacking trip in the Colorado Rockies.  The only light the group was exposed to during this time was natural lighting, namely sunlight, moonlight, and campfire light (no flashlights, no smart phones, etc). 

When they compared the circadian rhythms between the electrical-lighting and natural-lighting stages of the experiment, they discovered a few interesting things. The participants were exposed to approximately 4 times more light on the backpacking trip as compared to the level of light exposure during their typical week. Their results also showed that the timing of the circadian clock shifted ~2 hours earlier although the total amount of time they slept remained about the same. 

Wright and his team also looked at melatonin, a hormone that helps regulate our sleep-wake cycle. Melatonin rises before sleep and decreases throughout the night until after wake time. During the electric-light stage of the experiments, the participants melatonin levels were still high several hours after they awoke, indicating they were out of sync with the circadian clock. This melatonin paradox has been reported before and feelings of sleepiness or lower cognitive performance may be a consequence of spending time in electrically-lighted environments. However, after exposure to natural light, the melatonin offset shifted to approximately 50 min prior to wake time. This suggests that if circadian timing is aligned with the natural light-dark cycle in nature, the low point in brain arousal would move to before the end of the sleep cycle--making it easier to wake up in the morning. 

This study is just the beginning, and Wright et al agree that they would like to conduct a follow-up study with subjects of different ages and different cultures, as well as those participants that may have sleep difficulties. In an article for the BBC (2), Wright spoke about the some of the results of the study and offered advice for applying these principles to everyday life: "Start your day off with a walk outside. At night reduce lights in the house, dim computer and electronic devices."

Obviously I would love to go camping every weekend, but most jobs rarely afford you the freedom to do that.  In the meantime, I will settle for morning jogs along the bay and reading novels (*cough* I mean, scientific papers) before I go to sleep.

References:

1) Wright et al. "Entrainment of the Human Circadian Clock to the Natural Light-Dark Cycle." Current Biology 2013,  doi: 10.1016/j.cub.2013.06.039

2) McGrath, Matt. "Carry on Camping--Can a week under canvas reset our body clocks?" BBC News Science and Environment. http://www.bbc.co.uk/news/science-environment-23530408. (Accessed 8 August 2013).