lunes, 27 de abril de 2020

Fighting Off Infections Through Sleep

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By Sara Ryding, B.Sc.Reviewed by Emily Henderson, B.Sc.

Sleep plays an important role in maintaining a healthy body, with its link to the immune system and fighting off disease becoming increasingly appreciated.

Healthy sleeping habits can help both prevent and overcome infections as sleep is associated with the production and release of various substances such as proteins and protein agonists.

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Preventing infections

Lacking sufficient sleep can increase the risk of infections. The main reason for this is the lack of cytokines.

Cytokines are proteins that participate in the immune response by targeting infection and inflammation. They are produced and released during sleep, which means that unhealthy sleeping habits can lead to a deficiency in these crucial proteins.

The severity of sleep loss on the immune system varies depending on how much sleep is lost, how long the problem persists for, and how individuals respond to it. For some people with chronic sleep loss, common vaccines such as the flu vaccine show reduced effectiveness because the body’s responsiveness to the vaccine is diminished.

Recovering from infections

In addition to preventing infections, there is evidence that good sleep can help in fighting off infections quicker.

The cytokines which can help prevent infection are also crucial in fighting infections in the body. Chief among these is interleukin 1 (IL-1), which has been studied at length concerning sleep. Other cytokines whose levels are linked to sleep include IFN-g, TNF-a, and IL-2.

In addition to cytokines, sleep can modify the percentage of certain cell subpopulations. The cells affected by this include CD4+, CD8+, and NK. Specifically, sleep deprivation has been linked to a rise in monocytes and NK cells.

These alterations can, in turn, lead to changes in phagocytic activity, which is crucial in the early stages of defense against foreign pathogens.

Another cell influenced by sleep is T cells, whose efficacy can be influenced by sleep. T cells, which attach to infected cells or other targets, need efficient binding to be effective in clearing infections.

During sleep, agonists such as GαS-coupled receptor agonists are present at naturally lower levels. Reduced levels of this agonist lead to integrins, which are crucial for T cells binding to their target, not being inhibited.

This has, in turn, been linked to enhanced T cell responses and is hypothesized to be one of the main ways in which sleep helps in fighting off infections.

In addition to cytokines produced during sleep being used to fight infections, the cytokines themselves can affect sleep. The finding that the immune system and sleep have a bidirectional relationship was mainly attributed to IL-1.

Neurons in the central nervous system that are reactive to IL-1 are centralized to areas implicated in sleep regulation. Infections, where cytokines are stimulated, can lead to signaling to increase sleep, which helps produce more cytokines to fight the infection.

Changes to sleep patterns are often among the earliest responses to infection.

The bidirectional relationship between infection and sleep can also complicate relationships between diseases and sleep. For example, some research suggests individuals with sleep disorder narcolepsy have higher rates of infection.

This has led to the debate of whether infection occurs due to disrupted sleep patterns, or if the narcolepsy itself could be caused by infection. The higher levels of antibodies to two bacteria (Streptococcus and Helicobacter pylori) suggests it may be autoimmune diseases that trigger the narcolepsy.

Advice on healthy sleeping habits

It is estimated that a quarter of the population of the U.S. does not get enough sleep. It is advised that to keep the immune system in the best possible shape, adults should aim for seven to eight hours of sleep each night.

If this is not possible for a variety of reasons, sleep can be regained with 20 or 30-minute naps twice a day. For teenagers, the recommended amount is eight to ten hours per night.

Many people struggle to get the required amount of sleep, due to work, stress, and environmental factors, among others.

Some habits can help in consistently getting enough sleep include going to bed and waking up at the same time (regardless of whether it is a weekend or a weekday), avoiding naps for six hours before bedtime, avoiding electronics for one hour before bed, avoiding disruptive elements in the bedroom (such as pets and noise), and avoiding caffeine in the evening.

Sources

SleepFoundation.org. How sleep affects your immunity. (2020). www.sleepfoundation.org/articles/how-sleep-affects-your-immunity
Imeri, L., and Opp, M.R. (2009). How (and why) the immune system makes us sleep. Nature Reviews Neuroscience. https://doi.org/10.1038/nrn2576
Dimitrov, S. et al. (2019). GαS-coupled receptor signaling and sleep regulate integrin activation of human antigen-specific T cells. Journal of Experimental Medicine. https://doi.org/10.1084/jem.20181169
Ibarra-Coronado, E.G. et al. (2015). The bidirectional relationship between sleep and immunity against infections. Journal of Immunology Research. https://doi.org/10.1155/2015/678164
Stahl, S.M. and Sigua, N.L. (2016). Healthy sleep in adults. www.critcaremd.com/.../Healthy_sleep_in_adults.pdf