Sleep & Immunity

In this 24/7 society, being busy seems to be the ultimate state-of-mind. We are willing to compromise on rest, not productivity. We wake up early, we work late and we chug coffee to stay awake. Life is short, so why spend it asleep, right? Wrong!

Sleep is vital for our health. Whilst studies have shown humans to survive starvation for 21 days, a human can only last 11 days without sleep.

A 2016 scientific review uncovered that the deterioration of sleep in modern society was associated with an increasing susceptibility to illness such as flu and airway infections. It appears that sleep deprivation makes people less productive, not more.

So why is sleep so important for our immune system?

Our immune system is an extremely complex and well-oiled machine, with four functional features:

  • Exclusion barrier: This is what prevents pathogens from invading us in the first place
  • Recognition: If pathogens do invade, they are recognised and a response is initiated
  • Elimination: Stressors, such as pathogens or damaged cells, are eliminated by the correct response
  • Memory: Immune cells remember the previous pathogenic encounters, making response to the same pathogen next time much faster

These are multistep functions, which are tightly regulated to prevent malfunction. Failure in these controls can lead to immunodeficiency, or on the other hand, autoimmunity and allergies.

Interestingly, sleep and immunity are linked.

In the early stages of sleep, our bodies experience an ‘inflammatory peak’ which serves to promote growth, proliferation and specialisation of immune cells. That’s also when our immune system memorises pathogens it has encountered, producing long-lasting protection. Studies have found that people who slept after a vaccination developed better immunity than those who were sleep deprived. The inflammatory state experienced during sleep helps clean up damaged and infected cells and prepares our immune system for the day ahead. Some research suggests that this prep occurs whilst we are sleeping, because it requires a lot of energy. So, it makes sense to do this overnight, when we are not spending energy going about our daily lives. This also ensures that we are not feeling sluggish and sleepy from inflammation.

At the end of sleep and during wakefulness, anti-inflammatory signals kick in, shutting down the pro-inflammatory ones. This drives the production of more specialised cells that are able to deal with immediate threats we encounter in the environment.

Research suggests that lack of sleep puts our bodies under a state of stress, and out of balance. In fact, prolonged sleep deprivation (prevalent in our modern society) can lead to chronic low-grade inflammation, which is a risk factor for many illnesses. It’s been shown to result in immunodeficiency, making us more susceptible to infection, such as the common cold and flu. A 2016 review, for example, found that 9-5 shift workers had a potentially greater risk of contracting viral infection due to sleep deprivation. The long-term effects of sleep deprivation and sleep disorders have been linked to an increased risk of diabetes, obesity, depression, heart attack, and stroke.

A comprehensive 2017 meta-analysis, which looked at 40 cohort studies, enrolling 2,200,425 participants, recommended sleeping for 7 to 8 hours every day to reduce the risk of mortality.

With all this in mind, allow yourself to rest. The sleeping behaviour has survived thousands of years of evolution because it prepares us for the daily challenges. From immunity to alertness and general feel-good, sleeping may be the most productive thing you do all day!

References:

Besedovsky, L., Lange, T., & Born, J. (2011). Sleep and immune function. Pflügers Archiv – European Journal of Physiology, 463(1), 121–137. doi:10.1007/s00424-011-1044-0
Besedovsky, L., Lange, T., & Haack, M. (2019). The Sleep-Immune Crosstalk in Health and Disease. Physiological Reviews, 99(3), 1325–1380. doi:10.1152/physrev.00010.2018
Institute of Medicine Committee on Sleep, M. and Research. 2006. The National Academies Collection: Reports funded by National Institutes of Health. In: Colten, H.R. and Altevogt, B.M. eds. Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem.  Washington (DC): National Academies Press (US) National Academy of Sciences.
Kottusch, P., Tillmann, M. and Puschel, K. 2009. [Survival time without food and drink]. Arch Kriminol. 224(5-6), pp.184-191.
Liu, T.-Z., Xu, C., Rota, M., Cai, H., Zhang, C., Shi, M.-J., … Sun, X. (2017). Sleep duration and risk of all-cause mortality: A flexible, non-linear, meta-regression of 40 prospective cohort studies. Sleep Medicine Reviews, 32, 28–36. doi:10.1016/j.smrv.2016.02.005
Wilder-Smith, A., Mustafa, F.B., Earnest, A., Gen, L. and Macary, P.A. 2013. Impact of partial sleep deprivation on immune markers. Sleep Med. 14(10), pp.1031-1034.

Rusne Z

Rusne Z.

Rusne is a United Kingdom-based writer passionate about nutrition as treatment and prevention of illness. She is currently completing her Bachelor in Food Science and Nutrition at the University of Leeds, and has Research & Development experience in the reformulation of sugary soft drinks.

Apart from her studies, Rusne particularly enjoys cooking, travelling and exploring independent coffee shops.

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