Spending a winter weekend in the wilderness that exposes you to lots of natural light during the day—combined with absolutely zero artificial light at night—can reset your internal circadian clock and help you sleep better when you get home, according to a new study from the University of Colorado at Boulder.
The February 2017 two-study paper, “Circadian Entrainment to the Natural Light-Dark Cycle across Seasons and the Weekend,” was published today in Current Biology.
Wintertime can be especially disruptive to your circadian rhythms and internal chronobiological clock. In fact, the CU-Boulder researchers found that typical winter lifestyle and work habits reduce natural light exposure by a whopping 13 times compared to summertime sunlight exposure.
Circadian rhythms are the prime driving force of our wake-sleep chronobiological cycles. Despite the advent of artificial light, circadian rhythms have evolved since the beginning of time to stay synchronized with Earth's rotation and the rising and setting of the sun. When you spend too much time under artificial light without seeing enough natural light during the day, your circadian rhythms are thrown out of whack.
According to sleep researchers, disrupted circadian rhythms are associated with a broad range of health problems that include: sleep disturbances, reduced cognitive performance, mood disorders, diabetes, and obesity.
During their latest two-part research study, Kenneth Wright and his colleagues in the Sleep and Chronobiology Laboratory at CU-Boulder found that spending as little as two days camping in a remote area—far away from artificial indoor and outdoor light pollution—was enough to reset study participant’s internal clocks. This reset was measured by the timing of when melatonin levels began to rise in their bodies.
While the participants were camping, they went to bed earlier and slept longer. Upon returning home, their melatonin levels began to rise 1.4 hours earlier as their neurobiological perception of night aligned with the natural light-dark cycle of the season.
"Weekend exposure to natural light was sufficient to achieve 69 percent of the shift in circadian timing we previously reported after a week's exposure to natural light," Wright said in a statement to CU-Boulder.
In a 2013 paper, "Entrainment of the Human Circadian Clock to the Natural Light-Dark Cycle," Wright and his colleagues reported that camping for a week in the summer synchronized campers' internal clocks with the summer sun, and reduced insomnia when they got home. (I wrote about these findings in a Psychology Today blog post, "Why Is Camping the Ultimate Insomnia Cure?")
But after completing the 2013 research, Wright and his team still had more questions... Such as, "Just how quickly does the clock change in response to shifts in our light environment? And "How big of an impact do seasonal changes have on human biological rhythms?" Their curiosity to answer these questions led to their latest research and the new findings published today in Current Biology.
For anyone who wants to get his or her circadian rhythms back on track (but can't get away for a camping trip) Wright suggests getting more bright natural light by day and shutting off your smartphone and laptop at least an hour before going to bed. Previous studies have found that most digital devices emit "blue light" which is especially disruptive to circadian rhythms.
A November 2016 study by Matthew Christensen and colleagues from the University of California, San Francisco reported that nighttime exposure to smartphone screens is associated with lower sleep quality. The researchers found that smartphone use within 60 minutes of bedtime had the greatest impact on sleep disturbances. The findings were published in the open-access journal PLOS ONE.
To read more about the detriments of blue light and using digital devices before bed, check out my recent Psychology Today blog post, "Late-Night Smartphone Use Often Fuels Daytime Somnambulism”
One reason camping in a very remote region may be the ultimate cure for insomnia may also have to do with environmental light pollution. In June 2016, researchers reported that due to artificial outdoor ambient lights, one-third of humanity (and 80 percent of Americans) can no longer see the Milky Way at night.
The increased light pollution caused by global trends of urbanization is playing a bigger role in disrupting circadian rhythms and our natural sleep patterns than most experts anticipated.
From a historical perspective, human beings have only had broad access to electrical sources of light for about a century. Between 1878 and 1880, Thomas Edison and his team of inventors began testing 3,000 different potential light bulb designs.In November 1879, Edison filed the first patent for an electric lamp with a carbon filament that evolved into the light bulbs of today.
In 1882, Edison opened the first public electric company, Pearl Street Power Station, in lower Manhattan and began providing electricity to a handful of local customers. At the time, Edison declared, "We will make electricity so cheap that only the rich will burn candles." Electricity and artificial lighting didn't become widely available across the United States until the 1930s.
Based on how recently in our evolutionary biology artificial lighting became a part of daily lives, it’s not surprising that our modern chronobiological clocks are discombobulated. In summing up his research, Wright points out how a camping trip can help remedy modern day issues with circadian rhythms being out of sync,
"These studies suggest that our internal clock responds strongly and quite rapidly to the natural light-dark cycle. Living in our modern environments can significantly delay our circadian timing and late circadian timing is associated with many health consequences. But as little as a weekend camping trip can reset it."
Wright is optimistic that his team’s findings can help promote light-based architectural design approaches that will boost work performance and overall well-being by bringing more natural sunlight into the modern work environment. This could also help reduce seasonal depression and other circadian sleep-wake disorders year round, which could have profound benefits on public health and personal well-being.
Kenneth P. Wright, Andrew W. McHill, Brian R. Birks, Brandon R. Griffin, Thomas Rusterholz, Evan D. Chinoy. Entrainment of the Human Circadian Clock to the Natural Light-Dark Cycle. Current Biology, 2013; DOI: 10.1016/j.cub.2013.06.039
Ellen R. Stothard, Andrew W. McHill, Christopher M. Depner, Brian R. Birks, Thomas M. Moehlman, Hannah K. Ritchie, Jacob R. Guzzetti, Evan D. Chinoy, Monique K. LeBourgeois, John Axelsson, Kenneth P. Wright. Circadian Entrainment to the Natural Light-Dark Cycle across Seasons and the Weekend. Current Biology, 2017; DOI: 10.1016/j.cub.2016.12.041
Lanaj, K., Johnson, R. E., & Barnes, C. M. (2014). Beginning the workday yet already depleted? Consequences of late-night smartphone use and sleep. Organizational Behavior and Human Decision Processes, 124(1), 11-23. DOI: 10.1016/j.obhdp.2014.01.001
F. Falchi, P. Cinzano, D. Duriscoe, C. C. M. Kyba, C. D. Elvidge, K. Baugh, B. A. Portnov, N. A. Rybnikova, R. Furgoni. The new world atlas of artificial night sky brightness. Science Advances, 2016; 2 (6): e1600377 DOI: 10.1126/sciadv.1600377
Matthew A. Christensen, Laura Bettencourt, Leanne Kaye, Sai T. Moturu, Kaylin T. Nguyen, Jeffrey E. Olgin, Mark J. Pletcher, Gregory M. Marcus. Direct Measurements of Smartphone Screen-Time: Relationships with Demographics and Sleep. PLOS ONE, 2016; 11 (11): e0165331 DOI: 10.1371/journal.pone.0165331