Besides infancy, we don’t initially think of sleep as a big problem in childhood. Yet, a slew of recent articles have highlighted that insomnia and other sleep problems are not simply an issue of adulthood. A BBC Panorama documentary released last week commented on the surge in problems with sleep in children. Although there were a number of culprits identified for this increase in the problems with children’s sleep, one key point was technology and later exposure to artificial light.
We are all glued to our smartphones, laptops, and Fitbits. Modern artificial lighting allows us to work and entertain ourselves further into the night than natural light permits but the normality surrounding their use before bed is negatively influencing sleep. As people are educated more about the effects of technology on sleep, these issues should hopefully reduce but whether education can effect this change is uncertain. The question remains: How can we improve sleep without dragging people away from technology? One love-it or hate-it option may be camping.
Last month, a research group led by Kenneth Wright carried out two studies which examined how artificial light interferes with our natural sleep rhythms and our body’s concept of day and night. Study one assessed the sleep of participants firstly during artificial lighting and then natural lighting during the winter. The second study attempted to understand the impact of weekend camping on sleep. The researchers studied sleep by asking them to wear a watch to track movements and by tracking changes in a hormone called melatonin. Melatonin is released prior to sleep, reaches a midpoint during the first half of sleep and dips as you wake up. During the day, it is only detectable at trace levels because in the presence of light melatonin’s production is inhibited. This, in part, explains why we feel tired and want to go to bed at night rather than during the day. As a result, melatonin serves as a useful and precise marker of the internal biological night (i.e. when the body feels we should be sleeping).
The first study had participants spend a week, during winter, camping with no artificial light (e.g. torches or phones) and then a week in their normal, modern, environment which served as a baseline. Participants’ melatonin levels were measured during sleep after about 6 days of the modern environment and after 6 days of the natural light, camping, condition.
This initial study found that the internal biological night (e.g. melatonin onset, midpoint, and offset) is affected by seasonal fluctuations. Specifically, internal biological night is longer during winter and shorter during the summer. In the camping condition, melatonin onset and sleep onset were around 2 hours earlier compared to the modern, artificially lit, condition. However, melatonin offset and sleep offset were similar between camping and baseline. When comparing the winter data to previously collected summer data, the melatonin onset was earlier and melatonin offset was significantly later in the winter condition. More specifically, they showed a four-hour difference in internal biological night between winter and summer. However, there were no change in internal biological night between summer and winter offset when comparing the artificial light conditions. The modern, artificially lit, environment had extinguished the seasonal fluctuations in melatonin and sleep patterns.
The second study then went on to assess whether weekend exposure to natural light (i.e. camping) could help reduce the effects of social jet lag – the mismatch between the time you wake up during the weekday and weekend. We tend to delay our sleep during the weekend and this contributes to why it is so hard to wake up on a Monday morning. In this study, fourteen participants were first tested in their normal, artificially lit, environment and their melatonin levels during the night (onset, midpoint and offset) were assessed. Participants were then separated to a camping condition (n=9; natural light) or normal condition (n=5; artificial light).
What did they find? For the camping condition, the time at which participants went to sleep and woke up were similar between weekday and weekend. However, for the artificial light condition the onset of sleep was found to be delayed by almost 2 hours and participants woke up around an hour and a half later during the weekend compared to the weekday. People were staying up later and waking up later during the weekend presumably when they didn’t have work. Overall sleep duration and efficiency were similar across and within both groups. So, participants were not sleeping for longer under artificial light but were delaying their sleep schedule.
What about the data for internal biological night? In the camping condition, melatonin onset and midpoint were about an hour earlier during the weekend compared to weekday despite there being no changes in sleep timing. Interestingly, changes in melatonin were not only seen in the camping condition but also the modern setting. Melatonin onset, midpoint and offset were delayed by about an hour compared to the weekday for the modern, artificial light, condition. This is problematic if you have to get up earlier on the Monday morning for work and is linked to what we know as social jet lag. If you feel sleepier later and want to wake up later then you may find yourself being groggy and sleep deprived during the week.
Yet, when participants went camping over the weekend, they did not see a shift in their sleep onset or offset, and their biological night became advanced (started earlier) slightly. This suggests that weekend exposure to natural light (e.g. camping) may help diminish the negative effects of living in the current, high-paced, environment we currently have. The small sample size and short sampling period makes it hard to draw definite conclusions from this study but it does highlight that artificial lighting is having a definable impact on our sleep and the biochemistry underpinning it. It also provides some preliminary evidence of the biological impact of social jet lag.
You may, quite rightly, think that the results of this study are rather obvious: we stay up later during the weekend and our biology is going to follow suit unless we hike out to the middle of nowhere for the weekend. However, it highlighted the biological impact of our modern, well-lit, environment on our body’s internal clock. We know that using our devices before bed are generally bad for sleep but very few of us actually do anything about this. We may try to adopt better bedtime habits but this may be thwarted by technology (e.g. using a kindle to read just before bed)
Also, it is key to remember that light is not the only regulator of our sleep rhythms and in societies not exposed to artificial light the key determinant of the sleep cycle is temperature. This should make us think about not a single factor (i.e. light) but a multitude of issues may cause issues with our sleep. Interestingly, such individuals in cultures not exposed to artificial light also reported problems with insomnia but at a reduced rate than reported in modern society.
Nonetheless, light from devices, rich in low-wavelength blue-light, resets our biological clocks and inhibits the release of melatonin. As a result, we feel sleepier later even though we still have to get up at the same time and go to school, college or work. The recurrent sleep deprivation can in turn lower our mood, concentration and put us at increased risk of illness and metabolic disorders. Now, it is unlikely that the rise of childhood sleep problems can be fixed by wrenching tablets from children and throwing them out into the wilderness every Friday until Sunday. Nonetheless, we can think about what these devices are doing to our sleep – at the very least when we’re sleeping poorly to begin with.
Stothard ER, McHill AW, Depner CM, Birks BR, Moehlman TM, Ritchie HK, Guzzetti JR, Chinoy ED, LeBourgeois MK, Axelsson J, & Wright KP Jr (2017). Circadian Entrainment to the Natural Light-Dark Cycle across Seasons and the Weekend. Current biology : CB, 27 (4), 508-513 PMID: 28162893
Chang, A. M., Aeschbach, D., Duffy, J. F., & Czeisler, C. A. (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proceedings of the National Academy of Sciences, 112(4), 1232-1237.
Yetish, G., Kaplan, H., Gurven, M., Wood, B., Pontzer, H., Manger, P. R., … & Siegel, J. M. (2015). Natural sleep and its seasonal variations in three pre-industrial societies. Current Biology, 25(21), 2862-2868.