Sleep & Immune System
The understanding of how sleep and our immune system are connected is becoming more important as we normalize long working hours and shorten sleep duration. The powerful effects that sleep have on our immune system and vice versa have been extensively studied. Sleep science has been advancing throughout the years and it has become more apparent that people who do not get sufficient sleep are more likely to get sick and take longer to recover (Lack of Sleep: Can It Make You Sick? – Mayo Clinic, n.d.). This can be explained through biological evidence of what happens to our immune system when we sleep.
Firstly, we should understand our circadian rhythm, which is related to the physical, mental, and behavioural changes that follow a 24-hour cycle (Circadian Rhythms, n.d.). These changes are affected by the light and dark, and this includes when we feel sleepy and fall asleep easier. This system also regulates immunological processes. These immune functions have prominent rhythms that are synced with the circadian rhythm. For example, immune cells, like cytotoxic NK cells, peak during the wake period; whereas, immune memory cells like central memory T cells peak during the night (Besedovsky et al., 2012).
Getting enough sleep is essential to obtaining a balance in these immune cells which ensures we have a functioning immune system.
Additionally, sleep and the immune system have a bi-directional relationship. When we are sick, our sleep architecture is altered to increase the interaction between immune signaling molecules, like cytokine, and brain neurochemical systems, like serotonin (Besedovsky et al., 2012). It is hypothesized that these alterations are made to support the generation of fever. During the course of most infections, it was found that there is an increase in the amount of NREM sleep and a decrease in the amount of REM sleep (Besedovsky et al., 2012). If the infection goes on for a while, sleep patterns can be greatly altered by a poorly functioning immune system.
Another indicator of how sleep is connected to the immune system is that sleep disorders are often associated with chronic inflammatory diseases (Lorton et al., 2006). These chronic inflammatory diseases include rheumatoid arthritis, fibromyalgia and are often related to chronic fatigue syndrome (Lorton et al., 2006). Sleep can help us fight off infections and reduce the risk of catching a cold. Sleep should be considered a vital part of the immune system and we should not underestimate the importance of sleep.
Besedovsky, L., Lange, T., & Born, J. (2012). Sleep and immune function. Pflugers Archiv European Journal of Physiology, 463(1), 121–137. https://doi.org/10.1007/S00424-011-1044-0/FIGURES/4
Circadian Rhythms. (n.d.). Retrieved February 26, 2022, from https://www.nigms.nih.gov/education/fact-sheets/Pages/circadian-rhythms.aspx
Lack of sleep: Can it make you sick? – Mayo Clinic. (n.d.). Retrieved February 26, 2022, from https://www.mayoclinic.org/diseases-conditions/insomnia/expert-answers/lack-of-sleep/faq-20057757
Lorton, D., Lubahn, C. L., Estus, C., Millar, B. A., Carter, J. L., Wood, C. A., & Bellinger, D. L. (2006). Bidirectional communication between the Brain and the Immune System: Implications for Physiological Sleep and Disorders with Disrupted Sleep. Neuroimmunomodulation, 13(5–6), 357–374. https://doi.org/10.1159/000104864