To most people, it would be logical to follow that sleep is pretty important. However, in our busy society, sleep is often overlooked as a nuisance, something which disrupts our lives and can sometimes even be thought of as an illness which needs curing. So what really is the point of sleep? And is it our friend or our foe?
It is estimated that as humans, we spend 36% of our life asleep. To put this is another way, if we live to the age of 90, we will have effectively been asleep for 32 years of our life. To most people, it would be logical to follow that sleep is pretty important. However, in our busy society, sleep is often overlooked as a nuisance, something which disrupts our lives and can sometimes even be thought of as an illness which needs curing. So what really is the point of sleep? And is it our friend or our foe?
There are a number of different theories about why we sleep, one of them being that during sleep our brain processes and consolidates information. Research has shown that memory is better after sleep (Walker & Stickgold, 2004; BuzsÁk, 1998). In addition to this, it has been found that our ability to come up with novel solutions for complex problems is improved threefold after a good night’s sleep. So it would appear that sleeping helps our brain perform better during the day.
But what happens when we don’t sleep? While we are told that we should sleep for at least 8 hours a night as an optimum, it is common for adults to get as little as 5 hours sleep a night. Are there any negative side effects to this? It would appear so: after a certain amount of sleep deprivation, our brain begins to micro-sleep in an effort to recharge. It has been found that 31% of drivers micro-sleep while driving at some point during their lives. An alarmingly high number when you consider the damage that sleeping at the wheel could do. Furthermore, in the investigations following the incidents of Chernobyl and the space shuttle, it was stated that poor judgement as a result of extended shift work and lack of sleep were contributing factors. Effectively, when sleep deprived we have poor memory, increased impulsiveness, poor creativity, and poor judgement.
Sleep deprivation can also cause health problems such as weight gain (Patel et al., 2006), possibly due to the increased stress we feel when we are sleep deprived. Furthermore, there is evidence to suggest that there is a relationship between sleep deprivation and mental illness. For instance, it has been found that genes which are important in how we sleep can predispose people to mental illnesses such as schizophrenia (Wulff et al., 2010). It’s not all bad though: it is exciting to think that areas in the brain associated with sleep could become target areas for new therapeutic treatments.
Thomas Edison stated that “sleep is a criminal waste of time and a heritage of our cave days”. Whilst there is no dispute as to whether we need sleep, the question as to whether we get too much sleep have been overlooked. Many of us believe that we need 8 hours of sleep to function healthily and effectively. As mentioned earlier this could be a massive 30 years spent asleep. This, one could argue, is an avoidable waste of time. By sleeping 7 hours a night, just one hour less, you would regain an extra 4 years of your life awake.
Is it necessary to spend this much time asleep? The evidence suggests not. Hours 6-9 of sleep are phenotypically adaptable to shortening from external factors without causing a sleep debt or increasing daytime tiredness. This explains why many of us in 2013 only had 6.5 hours of sleep per night and functioned as well as those sleeping for longer. There is no correlation between length of sleep and quality of sleep. In fact, emerging evidence has indicated that longer sleep durations have been associated with poorer self-perceived health and greater psychopathology.
The true optimal levels of sleep, evidence suggests, is between 6.5-7.5 hours. Krispe et al. (2004) found in a study of 1.1million people that this sleep band had the lowest mortality. What’s more, sleeping for too long may in fact be harmful to your health. Studies have shown that women sleeping 8 hours per night were more likely to die in the following 6 years than those who had slept for 7 hours. Sleeping 8 hours or more has also been suggested to increase breast cancer risk by 6% and mortality by up to 30%. Consequently, though sleep is vital for human survival, many of us believe we require more sleep than we do, and this in turn could do more harm than good.
BuzsÁk, G. (1998). Memory consolidation during sleep: a neurophysiological perspective. Journal of Sleep Research, 7(S1), 17-23.
Horne, J. (2011). The end of sleep:‘Sleep debt’versus biological adaptation of human sleep to waking needs. Biological psychology, 87(1), 1-14.
Kripke, D. F., Garfinkel, L., Wingard, D. L., Klauber, M. R., & Marler, M. R. (2002). Mortality associated with sleep duration and insomnia. Archives of general psychiatry, 59(2), 131.
Patel, S. R., Malho, A., White, D. P., Gottlieb, D. J., & Hu, F. B. (2006). Association between reduced sleep and weight gain in women. American Journal of Epidemiology, 164(10), 947-954.
Walker, M. P., & Stickgold, R. (2004). Sleep-dependent learning and memory consolidation. Neuron, 44(1), 121-133.
Wulff, K., Gatti, S., Wettstein, J. G., & Foster, R. G. (2010). Sleep and circadian rhythm disruption in psychiatric and neurodegenerative disease.Nature Reviews Neuroscience, 11(8), 589-599.