The invention of the electric light bulb in the 19th century liberated us from the constraints of night and day, but at what cost to our emotional health?

Why do we sleep?
The origins and purpose of sleep are not yet fully understood, but it is clear that sleep plays an essential role in physiological and psychological homeostasis. Sleep is important for the regulation of mood, for growth and development, for the formation of long-term memories, and for maintenance of a healthy immune system (Choe 2010).
The quantity and quality of sleep are regulated by natural variations in light and darkness during the day (circadian rhythm), and during the year (seasonal variations). Human gene expression and signalling in response to light and darkness is very similar to that found in many other organisms (Ko & Takahashi 2006), which suggests sleep is important for survival.
Artificial light
Our non-human ancestors lived in world without artificial light. The introduction of fire, oil lamps and candles gave humans the possibility to extend daylight artificially, but these methods were relatively expensive, and their luminosity and wavelengths do not affect sleep adversely (Dennet 2001, pp 98-100).
Since the invention of the electric light bulb in 19th century, relatively cheap and bright artificial light has enabled a significant and increasing proportion of the human population to work, study and play at a time of their choosing. During the same period, there has been a 2 hour reduction in the average number of hours slept per night by adults in industrialised countries, and increasing uniformity across seasons: we no longer sleep for longer in the dark winter months (Dennet 2001, pp 98-100). Dennet (2001) argues that this has resulted in an epidemic of chronic sleep deprivation with grave consequences for our health.
The effects of sleep deprivation on the individual
Acute sleep deprivation impacts mood - fatigue, vigour and confusion - and stress (Minkel 2010). Chronic sleep deprivation has more serious consequences (see Table 1).
Affective dimension
  • Fear: worrying about waking on time
  • Frustration: cannot get to sleep
  • Anger: blame self or others for sleep loss
  • Anxiety and stress: fatigue impairs attention, concentration and memory, which impacts performance in personal and professional life; impaired immune system leaves us vulnerable to disease
  • Depression: disease, anxiety and chronic stress can lead to depression and, in some cases, suicide

Table 1. The affective consequences of chronic sleep deprivation
Mood can be affected directly and indirectly: for example, chronic sleep deprivation has been implicated in obesity (Dennett 2001), which can adversely affect self-image and leave the individual at risk of anxiety and depression. Depression can be both a cause and effect of sleep loss, which can lead to a downward spiral of depression and sleep deprivation.
These effects can be exacerbated by individual and cultural attitudes in terms of the quantity, quality, utility and even moral value of sleep.
Sleep can also be affected by psychiatric conditions. For example, due to chronic problems with time management and procrastination, individuals with Attention Deficit Hyperactivity Disorder (ADHD) are more likely to stay up late to work or study, and thereby forgo sleep, which would have been difficult or impossible before the invention of electric light.
The effects of sleep deprivation on society
The aggregate effect of increasing morbidity and mortality is costly to society as well as individuals, from the treatment of physical and psychological illness in our health systems, to income lost through illness and premature death.
Sleep deprivation impacts safety-critical systems. For example, an air traffic controller was asleep while two aircraft landed without guidance (Williams & Mouawad 2011), putting lives at risk - the focus of news reports were on the work place, but did the home environment and cultural attitudes towards sleep have an effect?
Opportunities for Human-Computer Interaction (HCI)
Many people are not aware of their sleep behaviours and the consequences of sleep deprivation (Dennett 2001).
Sleep has been given little attention in HCI, yet there are many opportunities for technology to help monitor sleep and maintain conditions for healthy sleep (see Figure 1):
Figure 1. Technology design ideas (Choe 2011):
(Left) Unobtrusive sleep monitoring tool uses a weight sensor under the bed to estimate sleep times and wake times.
(Middle) Role playing game where the player’s character only heals when the player actually rests in real life.
(Right) To help support a good sleep environment, this tool uses sensors to measure the room temperature, light, and sound and changes light colors as a simple indication if one or more conditions is not ideal.
Sleep monitoring can be combined with mood diaries and physiological observations in clinical settings, such as in sleep laboratories or as part of a programme of cognitive behavioural therapy (CBT).
The limits of technology
The ethical issues around such technology include privacy and trust - the bedroom is a place of intimacy as well as sleep - and yet the costs of doing nothing are high, particularly for vulnerable members of society (children, older adults and the disabled).
Moreover, good design and engineering have their limits, particularly where there are strong economic and social disincentives that undermine sleep. Fundamental changes in economies and societies usually require shifts in cultural values, not just technological solutions.
If awareness is the first step to such shifts, then design solutions combining elements of of ubiquitous computing (Rogers 2009) and behavioural economics (Dolan 2010) may offer some promise.
Choe, E. K., Kientz, J. A., Halko, S., Fonville, A., Sakaguchi, D., & Watson, N. F. (2010). Opportunities for computing to support healthy sleep behavior. Proceedings of the 28th of the international conference extended abstracts on Human factors in computing systems CHI EA 10, 3661. ACM Press.
Dolan et al (2010). MINDSPACE: Influencing behaviour through public policy. Institute for Government.
Ko, C. H., Takahashi, J. S. (2006). Molecular components of the mammalian circadian clock. Hum Mol Genet 15: R271-R277.10.1093/hmg/ddl207. PubMed: 16987893.
Minkel, Jared D. (2010). Affective Consequences of Sleep Deprivation. Publicly accessible Penn Dissertations. Paper 218.
Rogers, Y. (2009). The Changing Face of Human-Computer Interaction in the Age of Ubiquitous Computing. In A. Holzinger and K. Miesenberger (Eds.), USAB 2009, LNCS 5889, 1-19.
Williams & Mouawad (2011). Air Traffic Controller Is Suspended. New York Times 24 March 2011
Young & Bramham (2007). ADHD in Adults: A Psychological Guide to Practice. John Wiley and Sons: Chichester