"Carry on camping – can a week under canvas reset our body clocks?" BBC News asks.
The study in question looked at the effects of artificial light on the human body clock compared with natural light.
This was a small experimental study involving eight adults. The participants spent one week carrying out normal daily activities while being exposed to a normal pattern of outdoor light and indoor electric light. They then spent one week camping outdoors with only natural light and firelight and no electric light available.
During the study the researchers measured the participants’ melatonin levels. Melatonin is a hormone that controls the sleep–wake cycle. The researchers found that during the week spent outdoors there was a tendency for the participants’ body clocks to coincide better with sunrise and sunset.
The researchers suggest that synchronising the body clock with sunrise and sunset improves physical and mental wellbeing.
This study casts an interesting light on how our electrically lit environment may have altered our body clocks. However, it is significantly limited by the fact that it included just eight people.
The long-term health benefits of having a body clock in tune with natural light have not been assessed. In fact, sleep quality did not differ between the two scenarios observed in this study, so it provides no evidence that camping could be a cure for insomnia.
Where did the story come from?
The study was carried out by researchers from the University of Colorado in the US, and was supported by a grant from the US National Institutes of Health.
The study was published in the peer-reviewed scientific journal Current Biology.
The UK media has slightly exaggerated the findings of this small experimental study in only eight people, from which no firm conclusions related to health or wellbeing can be drawn.
What kind of research was this?
This research is based on the theory that while the electric light was a wonderful invention for bringing us out of the dark, it may have disrupted sleep patterns and other natural rhythms of the body that evolved in a time when we were exposed to natural light–dark cycles.
The researchers wanted to explore the extent to which electric lighting may have altered the natural human body clock.
What did the research involve?
The study included eight participants with an average age of 30, two of whom were women. It took place in two weeks in July in the Rocky Mountains of Colorado, in the United States.
First of all the researchers assessed each individual’s chronotype. A chronotype is a summary of an individual based on sleep-related factors, such as:
- the timing of their individual body clock
- what time of the day their physical functions, such as hormone levels and body temperature are at their peak
- when they are best suited to going to bed and getting up
This was assessed using the Morningness-Eveningness Questionnaire (MEQ), and the Munich Chronotype Questionnaire. From these assessments, one person was defined to be a definite evening type, one a moderate evening type, four intermediate and two moderate morning types.
They were first examined for one week spent carrying out their normal daily activities (for example normal routines of work, social activities and self-selected sleep schedules) and living in a constructed electric light environment. In this environment participants were exposed to an average 979 lux during waking hours. Lux is a measurement of light exposure over an area of a square metre – a full moon on a clear night will give around 0.2 to one lux.
This lighting was meant to be representative of the average lifestyle of participants in the sunny climate of the mountain-desert region of Colorado.
This was then compared to one week of outdoor camping in tents with exposure to only natural light with sunlight and campfires, but with no torches or personal electronic devices.
During the two-week period participants wore wrist activity monitors that also measured light levels. These were used to assess weekly average activity levels, start of sleep, sleep duration, time of waking and sleep efficacy (a measure of time spent asleep, taking into account light exposure levels).
After each of the two lighting conditions, participants also attended the laboratory overnight to have regular saliva samples taken to measure melatonin (a hormone that regulates the human body clock).
Peak melatonin levels and lowest levels (onset and offset) are said to represent, respectively, the beginning and end of the internal biological night.
What were the basic results?
The researchers found that the participants’ average light exposure was four-fold greater during the week of natural outdoor lighting than the week spent in the constructed electric light environment.
While living in the outdoor environment, participants were exposed to significantly more light during the first two hours after waking. They also spent a greater proportion of hours of the waking day at higher light levels than when in the constructed environment.
The only time of day when participants were exposed to more light in the constructed electric light condition was between sunset and sleep start time.
When looking at melatonin levels, after spending the week in the electric light environment melatonin onset occurred around two hours before sleep time (at around 12.30am) and offset occurred after wake time (at around 8am).
After the week in natural outdoor lighting there was a shift in this pattern. Melatonin onset and offset occurred about two hours earlier, with onset occurring closer to sunset, and offset occurring before waking at sunrise.
The change in melatonin was associated with a change in sleep times, with about a 1.2 hour difference between the two conditions in timing of sleep start and waking. However, there was no significant difference between the two conditions in sleep duration or sleep efficiency.
The researchers also observed that later chronotypes (‘evening people’) showed greater changes in their body clock when exposed to only natural light. This made the timing of their internal clocks in relation to the light–dark cycle more similar to earlier chronotypes (‘morning people’).
How did the researchers interpret the results?
The researchers conclude that their findings have important implications for understanding how modern light exposure patterns contribute to late sleep schedules, and how this may disrupt sleep patterns and the natural body clock.
Overall, these findings are of interest in their exploration of how our electrically lit environment may have altered our body clock. However, no real conclusions or implications for health or lifestyle can be drawn from this study.
The study included only eight US adults and exposed them to a brief, two-week experimental scenario. The patterns observed during these brief experimental periods when participants were being monitored may not relate to their own sleep patterns when in their normal everyday life. Neither can the results from eight people be applied to the wider general population – and especially not to people suffering from insomnia or other sleep disorders.
It is an interesting theory that our body clock may work better if we are exposed to natural light only, but while this may be feasible in the summer, this would be impractical in winter in the longer term.
More well established methods to combat insomnia include:
- creating a restful sleeping environment
- making sure that your bed is comfortable
- exercising regularly
- drinking less caffeine
Read more advice in the Better sleep.