A good night’s sleep is one of the most important human needs, particularly in the hustle and bustle of contemporary society. However, many of us are beginning to prioritise other aspects of our lives; work, family and social commitments, even entertainment like movies and internet use, leaving sleep as a final consideration. It was found that one hour of less sleep due to the change of daylight savings time at the beginning of spring, resulted in a 24% increased number of heart attacks the next day. While the extra hour of sleep we gain in reverse of daylight savings time, a 21% reduction in heart attacks was found [11].
The effects of sleep deprivation are real and damaging. While most of us know that we should probably be getting more sleep, we are not fully aware of the physiological toll that a lack of sleep presents.
Sleep deprivation can lead to the development of obesity through the dysregulation of our hunger and satiety hormones [9]. When sleep deprived, the hormone responsible for inducing hunger, known as Ghrelin, is increased. In addition, the hormone Leptin, which signals satiety (feeling full) to the brain, is decreased [9]. Not only do we eat more when we are tired, but we also seek out and prefer unhealthier, high-calorie foods [5].
Let’s take two groups of people. One group will be sleep deprived to around 4 hours of sleep, while the other will have a full night’s sleep of 8 hours. In the morning, there is a buffet of foods and snacks, everything from healthy salads and whole foods, to candies and other unhealthy treats. If we observe the food that both groups select, you will find the sleep-restricted group will consume around 300 calories more than the well-slept group [6].
The areas of the brain responsible for conflict monitoring, avoiding and the sense of feeling and understanding your body (interoception) are reduced under a lack of sleep, which is believed to contribute to the increase in desire of unhealthy foods [5]. Trying to stick to a healthy diet or lose weight is going to be that extra degree more difficult if we do not get appropriate sleep.
Sleep deprivation has been associated with depressive symptoms, increases in anxiety, stress, and negative mood states [4, 7, 8, 12]. In fact, the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), lists insomnia as a factor in diagnostic criteria of major depressive disorder [1]. A lack of sleep produces increases in activity in the amygdala, the area of the brain related to negative emotions [4] and increases in sympathetic nervous system activity, resulting in increased stress and reactivity [13]. Increases in inflammation has also been found in sleep-deprived individuals [9], which has been linked as a contributing factor to depressive mood, increases in anxiety and stress. (Read more about inflammation)
If obesity and depression weren’t enough, sleep deprivation may also take your cognitive functions and memory. Sleep acts as a rehearsal and reactivating activity for memories and skills. It has been shown that activity patterns learned during wake are ‘replayed’ during sleep, which suggests that sleep strengthens our learned skills and consolidates memories [10]. Reducing sleep would therefore reduce the play-back time required to remember skills and memories. Prolonged wakefulness has been shown to reduce attention, learning and executive function [2, 14]. For this reason, staying up all night to study for an upcoming exam would be a terrible idea.
With all the science available on the detrimental effects of sacrificing our sleep, we should reconsider the importance of scheduling time in our busy calendars for one of the most important recovery activities in our lives.
References:
1. American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Arlington, VA: American Psychiatric Publishing.
2. Arnal, P. J., Sauvet, F., Leger, D., Van Beers, P., Bayon, V., Bougard, C., ... & Chennaoui, M. (2015). Benefits of sleep extension on sustained attention and sleep pressure before and during total sleep deprivation and recovery. Sleep, 38(12), 1935-1943.
3. Chiang, Y. C., & Arendt, S. W. (2017). Benefits of Sleep for Undergraduate Students’ Academic Performance. Journal of Hospitality & Tourism Education, 29(2), 61-70.
4. Goel, N., Rao, H., Durmer, J. S., & Dinges, D. F. (2009, September). Neurocognitive consequences of sleep deprivation. In Seminars in neurology (Vol. 29, No. 4, p. 320). NIH Public Access.
5. Greer, S. M., Goldstein, A. N., & Walker, M. P. (2013). The impact of sleep deprivation on food desire in the human brain. Nature communications, 4, ncomms3259.
6. Hanlon, E; Tasali, E; Leproult, R; Stuhr, K; Doncheck, E; de Wit, H; Van Cauter, E (2016). Sleep restriction enhances the daily rhythm of circulating levels of endocannabinoid 2-arachidonoylglycerol. Sleep, 39(3), 653-664.
7. Ji, X. W., Chan, C. H., Lau, B. H., Chan, J. S., Chan, C. L., & Chung, K. F. (2017). The interrelationship between sleep and depression: a secondary analysis of a randomized controlled trial on mind-body-spirit intervention. Sleep medicine, 29, 41-46.
8. Lovato, N., & Gradisar, M. (2014). A meta-analysis and model of the relationship between sleep and depression in adolescents: recommendations for future research and clinical practice. Sleep Medicine Reviews, 18(6), 521-529.
9. Mullington, J. M., Haack, M., Toth, M., Serrador, J. M., & Meier-Ewert, H. K. (2009). Cardiovascular, inflammatory, and metabolic consequences of sleep deprivation. Progress in cardiovascular diseases, 51(4), 294-302.
10. Nere, A. T., Hashmi, A., Cirelli, C., & Tononi, G. (2013). Sleep-dependent synaptic down-selection (I): modeling the benefits of sleep on memory consolidation and integration. Frontiers in neurology, 4, 143.
11. Sandhu, A., Seth, M., & Gurm, H. S. (2014). Daylight savings time and myocardial infarction. Open heart, 1(1), e000019.
12. Short, M. A., & Louca, M. (2015). Sleep deprivation leads to mood deficits in healthy adolescents. Sleep medicine, 16(8), 987-993.
13. Spiegel, K., Leproult, R., & Van Cauter, E. (1999). Impact of sleep debt on metabolic and endocrine function. The lancet, 354(9188), 1435-1439.
14. Vyazovskiy, V. V. (2015). Sleep, recovery, and metaregulation: explaining the benefits of sleep. Nature and science of sleep, 7, 171.
