Sleep is a great protector of your immune system; it fights against infection and, if you do happen to fall ill, sleep is deployed to encourage rest and recuperation. On the other hand, it doesn’t take many nights of short sleeping to weaken your immune resilience.
Sleep is therefore a simple way to support the immune system in its fight against colds, flu, and other respiratory infections. This is supported by decades of scientific research, suggesting that sleep may be a powerful ally in the battle against the pandemic, and not only by reducing the likelihood or severity of infections. Sleep may also boost the effectiveness of any COVID-19 vaccines (when they become available), and studies are well underway investigating the health defences we gain against the Coronavirus by getting some decent shut eye.
“We have a lot of evidence that if you have an adequate amount of sleep, you definitely can help to prevent or fight any kind of infection,” says psychoneuroimmunologist, Monika Haack (Harvard Medical School). “How many deaths can you prevent if you sleep properly?...I think that needs more research.”
Until we have a vaccine available, the only way to avoid COVID-19 is by reducing your risk of infection as much as you can. Scientists are busy working on further understanding the complex immune system, and providing clearer advice on how sleep can be harnessed to ward off the pandemic.
THE INFECTION CONNECTION
Prolonged sleep deprivation has long-term consequences, increasing the risk of type 2 diabetes, cardiovascular disease, dementia and depression. Some of those conditions are among the risk factors that can increase susceptibility to COVID-19.
Growing evidence demonstrates that sleep deprivation weakens a person’s ability to fend off disease once infected. Some have even tracked the journey directly from sleep to illness; a study by Dr Aric Prather at the University of California demonstrated a clear link between sleep and illness: the less sleep an individual acquired in the week leading up to exposure to the common cold virus, the higher their chances of catching a cold. Almost half of the participants who slept an average of five hours became infected, compared with just 18% of those who achieved seven hours or more. While the virus was equally likely to invade participants’ bodies and replicate, irrespective of sleep, those who got less than six hours of shut eye in the run up to exposure were 4.5 times more likely to develop symptoms, when compared to those who slept for more than seven hours.
Not only that, but studies of colds and flu have indicated that infected people with poor sleep suffer worse symptoms.
In addition, when tired, people are more likely to engage in risk-taking behaviours. In terms of the pandemic, that could translate as being slack with mask-wearing or hand-washing, potentially piling extra pressure on the immune system.
THE SLEEP/IMMUNE SYSTEM MYSTERY
Studies have started to unravel the mystery of how exactly sleep impacts the immune system; “We know that you need sleep to fight infections,” Haack says. “But how exactly it works, I think there's still a lot of work to do.”
A 2019 study, by Haack and colleagues, specified more than 35 ways that various immune-system components alter based on sleep changes. For example, T cells are are often described as the soldiers that battle infections. According to studies by German researchers, during sleep T cells normally move out of the blood and likely into lymph nodes, where they look out for invading pathogens, Haack says. But studies show that just one night of sleep deprivation is enough to keep T cells circulating in the blood, rather than moving out as described, making them less able to learn about, respond to and fight viruses.
Cytokines, a type of inflammatory molecule connected to the COVID-19 pandemic, are also a focus of research on sleep and the immune system. Normally, pro-inflammatory cytokines help organize an immune response to infections, prompting other cells to join the fight, says psychoneuroimmunologist, Sheldon Cohen (Carnegie Mellon University). But the production of too many of these molecules creates a ‘cytokine storm’, an overreaction which has been linked to severe and fatal cases of COVID-19.
SLEEP AND VACCINES
Vaccine research has offered an interesting opportunity to investigate the link between sleep and the immune system.
In a 2002 study, one group of people had around eight hours of sleep for four nights before getting a flu vaccination, then slept the same amount for the two nights following the vaccination. Ten days later, researchers noted their influenza antibody levels (proteins the body makes in response to pathogens and vaccines, that help the body remember those infections to better fight them) were more than twice as high as those in people who had slept only four hours per night over the same period. Studies have shown similar impacts of sleep deprivation on hepatitis A, hepatitis B and H1N1 swine flu vaccines.
Those increased antibody levels led to significant reported health outcomes, even in the long term. One study connected better sleep before getting the hepatitis B vaccination with a lower chance of getting the disease for the next six months!
Given the rush to develop a COVID-19 vaccine to combat the pandemic, a simple behaviour that could boost its effectiveness would be a real positive. At the Walter Reed Army Institute of Research’s Center for Military Psychiatry and Neuroscience Research in Maryland, researchers are working on a COVID-19 vaccine. When its phase one clinical trial begins this winter, Lt. Col. Vincent Capaldi (chief of the Department of Behavioral Biology) says they plan for one group of participants to sleep up to 10 hours per night leading up to the day of vaccination, to see the impact.
Further insight around the sleep/vaccine connection could also benefit efficient vaccine distribution for frontline healthcare workers, especially those who have worked consistently long hours during the pandemic already. It may be that they need to rest before vaccination to improve its effectiveness. “This could have such important relevance to vaccination policy,” says Prather. “Anything that we can do to try to enhance a response seems really important.”
CONCLUSION
Researchers are now working through huge amounts of data to link sleep with COVID-19 risk. While nothing has been published to date, Haack says she has reviewed multiple upcoming studies, and the results seem promising.
Indeed, existing studies show that a full night of sleep has a multitude of healing benefits, alongside helping you fight infection, including relaxing your body’s fight or flight instincts, which in turn helps manage your blood pressure, providing some protection from a heart attack or stroke. It also results in a significant increase in the removal of dangerous brain waste including the removal of amyloid, a poisonous protein linked to Alzheimer’s disease. While more research needs to be carried out, hopeful support has developed for the theory that, by improving sleep, the risk of developing Alzheimer’s disease can be reduced or its onset delayed.
Sleep is, of course, not the only factor that affects susceptibility to illness; social situations, stress, smoking, alcohol consumption and other factors will play a role. But experts still advise prioritising sleep, given its relationship to risk of infection.
So if you can, implement a consistent sleep schedule this winter. And take a break from screens for a couple of hours before – ipads, laptops, phones etc emit blue light which can keep you awake – and especially the news (as it can cause bedtime worry!).
Sheldon Cohen recommends sleeping at least seven hours a night to improve your chances of staying healthy during the pandemic. “Over and over, we show that people who got insufficient amounts of sleep were more likely to get sick when we exposed them to a virus,” he says. “It clearly plays a role in health and well-being.”
NB: This article is for information purposes, and does not constitute medical advice. If you are experiencing difficulty sleeping, or have symptoms which prevent you from sleeping well, you should contact your medical practitioner.
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