Authors: Anna Myers B. AppSci (ClinSci)/B. Osteopathy and Dr Ian C Dunican PhD, MBA, MMineEng, GCASSc, BA
Australia and many other countries in the southern hemisphere are coming into the cold and flu season and while COVID-19 has caused significant changes to the workplace and social hygiene practices, the importance of other behaviours for good health and immunity should not be underestimated.
Studies have shown that getting <6 hours of sleep per night potentially increases the chances of getting the common cold [2,9] and reduces our immune response to such infections  and may reduce the efficacy of certain immunisations . Whereas for adults, sleeping for 7-9 hours can positively impact our immune system [1,7]. On a daily basis, sleep duration can influence the ability to resist infection. Shorter sleep in the night has been demonstrated to increase the chances of getting a cold  by almost 3 times compared to those who sleep for 7-9 hours . Sleep efficiency (quality or percentage of time we spend asleep whilst in bed) is also important as there is a strong correlation between becoming infected with a cold and poor sleep efficiency . More significantly, to reduce the chance of serious illness this winter, 62% of Australians intend to get the flu vaccine . Sleep duration has the potential to affect this .
Immunisation takes advantage of adaptive immunity; the immune system’s ability to learn from an initial exposure to a pathogen; virus, toxin, or bacteria, and to create a stronger, faster, and more efficient immune response when exposed again [3,10]. A modified version of the pathogen is introduced to the body to stimulate the body to create immunity [3,10]. On first exposure to the modified pathogen (immunisation or infection) the immune system creates a fast, general response (Innate Immunity) while establishing the slower but more specific response (Adaptive Immunity). The adaptive response creates cells (B and T cells) that are capable producing substances such as antibodies, chemokines and cytokines and recruiting other cells that can recognise and destroy the pathogen [5,10]. Some of the T cells develop a memory for the key aspects of the pathogen, so at re-exposure, the adaptive arm of the immune system can respond quickly, reducing the chance of becoming unwell [3,10].
Chronic short sleep deprivation has been demonstrated to decrease immune antibody response to the flu vaccine by half compared to longer sleep the night after immunisation . Whereas getting adequate sleep has been shown to have a positive effect on immunisation response. [7,8]. A study on the Hepatitis B immunisation series showed that less than 6 hours sleep per night compared to 7 hours or more around the time of immunisation resulted lower levels of antibodies in response the vaccine and a lower rate of clinical immunity six months post immunisation . The higher levels of antibodies and immunisation efficiency, seen in the group who slept longer, were measured after the second and third immunisations, indicating sleep had an influence on the adaptive immunity . A Hepatitis A immunisation study also found higher antibody production and a stronger adaptive response 1year post immunisation in those who slept for 7 hours on the night of immunisation .
Getting 7-9 hours’ sleep per night allows the body to achieve the required time in stages of sleep [1,6]. The integration and consolidation of adaptive immunity is strongly associated the third stage- slow wave or deep sleep [1,6]. Due to the influence of homeostatic and circadian rhythms in the body, this stage occurs most strongly in the first half of sleep, with sleep getting lighter in the second half [1,6]. Getting regular nightly sleep of 7-9 hours not only helps ward off common infections but can be especially helpful to creating immunity post immunisation [1-3, 5-11].
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