Sleep and the immune system

Sandy Watts


Has your sleep been disrupted recently?

In these unsettling times of Covid-19, sleep disruption is hardly surprising.

How does poor sleep impact the immune system?

Sleep is a driver of impaired immune function. 

It stands to reason that the ability to fight infection will be compromised in the face of poor sleep quality.

Sleep is the time when the body can ‘rest and repair’, recovering each night from the previous day, restoring and rejuvenating itself, ready for the next day.

Many people suffer from sleep disturbances, finding it difficult to fall asleep, or stay asleep, or both. Sleep deprivation is widespread in our modern society and is known to reduce immune defences and increase susceptibility to infections.

Total and even partial sleep deprivation results in alterations in immune parameters critical to host resistance, such as diminished T cell proliferation, shifts in T helper cell cytokine responses, and increased activation of pro-inflammatory pathways. T cells are a type of white blood cell which protect the body from pathogens such as viruses, while T helper cells ‘help’ by activating T cells and stimulating antibody production.

Sleep restriction reduces the cytotoxicity of natural killer (NK) cells that work to control viral infections. NK cells release cytotoxic (‘poisonous to the cell’) chemicals which recognise, target and kill virus-infected cells. Just 48 hours of sleep deprivation results in a decrease in NK cells, with a return to normal values following recovery sleep. 

Poorer sleep continuity and shorter sleep duration in the weeks preceding exposure to a rhinovirus (the common cold) were shown to be associated with lower resistance to illness, with people experiencing poor quality sleep and/or regular sleep deprivation (sleeping for less than 6 or 7 hours a night) having a 4-5 times greater risk of developing the common cold. 

Insufficient sleep has been shown to alter gene expression, reducing the immune response.

Short sleep duration may negatively affect antibody responses to novel (new, previously unseen) antigens (such as viruses). This provides a possible explanation for observed associations of poor sleep with increased susceptibility to infectious disease.

Ultimately, the consequence of sleep disturbance is a sustained inflammatory response, decreased antiviral response and increased susceptibility to infectious disease.

Why is good sleep so important at this time?

In contrast, adequate sleep enhances immune defences to help prevent viral infection.

Sleep is also an important means of recovery from infection and illness, enhancing immune defences and signals from immune cells which in turn promote sleep. In fact, the suggested function of sleep is to stimulate immune defence. Metabolic demands during sleep time are low, and the immune system is able to regulate both ‘innate’ and antiviral immune responses, preparing for any challenges the following day.

The ‘innate’ immune response refers to the body’s natural resistance, or ‘first line of defence’, and consists of physical barriers such as the skin, gastric acid, digestive enzymes, tears and mucous. Innate immunity also includes the ‘second line of defence’. This includes a process known as ‘phagocytosis’ (whereby phagocytes, a type of white blood cell, ‘eat’ or consume foreign ‘invaders’), the work of the NK cells which kill abnormal cells, and the process of inflammation (including fever). Inflammation is a rapid, non-specific defence that helps to limit the spread of foreign substances and helps to activate ‘adaptive’ or learned immunity, developed as an individual is exposed to antigens such as viruses. 

The adaptive response performs more slowly than the innate system, however it is more powerful and precise, selectively targeting invaders that it has identified. T cells work to kill targets directly, or stimulate other white blood cells (B cells) to create protective antibodies. The innate and adaptive sections of the immune system work on different levels, but work together to protect the body from foreign substances including viruses.

Sleep and immunity are bi-directionally linked. Immune system activation alters sleep, and sleep in turn affects both the innate and adaptive arms of the body’s defence system. Stimulation of the immune system by microbial challenges triggers an inflammatory response, which, depending on its magnitude and time course, can bring about an increase in sleep duration and intensity.

Acute immune activation promotes sleep, however in the face of chronic stress and/or inflammation, the normally adaptive function of sleep is disrupted. When this occurs, the immune system becomes more pro-inflammatory and its antiviral function less proficient. Those who suffer from sleep disturbance and have high variability in sleep duration between nights, also have higher levels of C-reactive protein (CRP) and IL-6, indicative of inflammation. It is believed that enhancement of sleep during an infection feeds back to the immune system to promote immune defence. 

Adequate sleep helps the body to mount an antibody response. Sleep duration is positively associated with secondary antibody response to vaccination and likelihood of clinical protection. This suggests that strategies to support ensuring adequate sleep would therefore appear to be sensible preparation for vaccinations to improve their clinical effectiveness.

Adequate sleep is associated with a reduced infection risk, and can also improve infection outcome and responses to vaccinations. 

How can a naturopathic approach help to improve my sleep?

Sleep as medicine.

If you haven’t been sleeping well recently (understandable!), a naturopathic approach could help you to improve your sleep, in turn helping to support a healthy, robust, resilient immune system.

Sound sleep strategies involve lifestyle and dietary considerations, as well as various herbal and nutritional medicines and supplements, including liquid herbal extracts, capsules, tablets, or medicinal teas, depending on what’s going to be best for you. These natural medicines can induce and support optimal sleep, as well as help to alleviate anxiety and reduce nervous tension, and increase the body’s resistance and adaptation to stress.

A naturopathic approach can help to address the cause of compromised sleep, and help you to identify ways to build good sleep habits and sleep hygiene practices that will work for you. 

By optimising sleep it is possible to improve immune defence responses and the ability to resolve infections, and lessen the impact on the body of a viral infection.

While obviously we must consider the role of the pathogen in disease presentation, it is also important not to lose sight of the bigger, overall picture of health – to ensure a robust, resilient immune system.


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