Bensons’ sleep expert Dr Sophie Bostock highlights importance of sleep as nation gets vaccinated...
In December 2020, the first NHS patient was vaccinated against coronavirus, marking a dramatic change in our approach to defeating the virus. Up until then, our main tool was avoidance; national lockdown, face masks, social distancing, hand washing - all these initiatives aim to prevent the spread of infectious virus particles from one person to the next. The vaccine marks a change from avoidance alone towards strengthening our individual capability to defeat the disease.
All 3 vaccines work by training our immune system to recognise the distinctive spike proteins on the surface of the covid-19 virus. Once we know how to recognise and respond to these spikes, we can produce targeted antibodies which can rapidly overwhelm and eliminate the virus, before it has time to take over.
Trials of the 3 vaccines approved so far suggest that they are extremely effective, preventing between 70-95% of those receiving the vaccine from developing covid-19 symptoms. We don’t yet know how long this immunity will last, but it’s likely to depend on how successful the body is at retaining the memory cells which can recognise the virus, and signal a strong attack.
How could we optimise the effectiveness of the vaccine?
No vaccine is 100% effective, because of the enormous variation in individual immune systems. There are some factors which can make the immune system less likely to work which we can’t change; for example, as we age, the immune system mounts a less powerful response. However, research has shown that lifestyle choices can also have an impact on immune defences.
Most people are aware that chronic stress, poor diet, smoking, alcohol and lack of exercise make them generally more vulnerable to infection. But does sleep also have a role to play?
Could more sleep reduce your risk of getting a viral illness?
So far, there hasn’t been any research published which explores the links between sleep and vulnerability to covid-19, but it is a potential avenue for research. We do know that short sleepers are more likely to contract another contagious viral illness: the common cold.
In one large study (Prather et al 2015), 164 healthy adults tracked their sleep at home for 7 nights, using a wrist monitor to record how long they slept. These brave volunteers were then exposed to the common cold virus, applied directly up the nose. Over the following 5 nights they stayed in a hotel and researchers followed up to see who became infected.
Researchers found that 76% became infected with the common cold virus, and 29% developed symptoms of the cold. But who was at greatest risk?
The number of hours of sleep in the week before exposure was the strongest factor predicting who developed a cold. Those who slept for less than 6 hours were over 4 times more likely to get a cold than those who slept for 7 hours or more. Those who slept for less than 5 hours per night were 4.5 times more likely to develop a cold than those sleeping for more than 7 hours per night.
The link between short sleep and risk of a cold was stronger than all the other characteristics investigated, including age, BMI, education, smoking, alcohol, stress and mood.
How are sleep and our immune system linked?
Our immune defences consist of several different varieties of white blood cells. First we need to recognise foreign bodies, and tag them so that the rest of the immune system can spot them. This can be tricky with viruses, since they typically reproduce using the body’s own cells. Once they’ve been recognised, other cells escort the invaders to the body’s lymph glands so they can be outnumbered and destroyed using poisonous cytotoxins, or by engulfing them. Memory B cells help recognise foreign proteins, orso that we can mount a speedy response by producing specific neutralising antibodies, which multiply rapidly if we see the same infection twice.
Studies in the lab have found that even one night without sleep can interfere with communication between immune cells, making the whole army less efficient, and causing more collateral damage, in the form of inflammation (Irwin et al 2016). Inflammation can be part of a healthy response to infection, but too much of it has been linked to chronic diseases, such as heart disease.
Sleep seems to be particularly important for T cell function. T cells help to identify invaders, send out cytokines (messengers) to tell the rest of the immune army what’s up, and start on destruction. Restricting sleep to 4 hours in healthy people can reduce the activity of our ‘natural killer’ T cells by 28% (Irwin et al 1994). A study published in 2019 showed staying awake all night interfered with the production of integrins, which help T cells to attach to, and kill, virus infected cells (Dimitrov et al 2019).
Could more sleep enhance the effectiveness of the covid-19 vaccine?
To date, there have been no published studies looking at the effect of sleep on the effectiveness of the covid-19 vaccine, so it is too early to say, but watch this space.
There is evidence that lack of sleep can interfere with the effectiveness of another virus vaccine - this time for Hepatitis B. Prather and colleagues (2012) found that after a routine Hepatitis B vaccine, >95% of those sleeping for 7 hours or more produced a clinically protective response, compared with fewer than 75% of those who slept for fewer than 6 hours in the week they received the vaccine.
The Pfizer covid-19 vaccine is already thought to have 95% effectiveness, so it’s unlikely that more sleep could make it even more effective, but it might be that sufficient sleep helps the immune system to maintain a protective response for longer.
Very few studies which have attempted to use better sleep to try and reduce infection risk. Michael Irwin from UCLA explored the impact of Cognitive Behavioural Therapy for Insomnia (talking therapy for insomnia) or Tai Chi in 123 elderly adults, compared with a sleep education control group (Irwin et al 2015). There was evidence that CBT-I reduced systemic markers of inflammation, even 16 months later. Tai Chi was also helpful against inflammation.
So, could better sleep make a difference?
It has been estimated that more than 1 in 3 of UK adults do not routinely get the recommended 7 to 9 hours sleep each night (RAND 2016). Getting the right amount of sleep makes us feel less stressed, more confident, more productive, and these studies also show that there is also evidence that it strengthens our immune defences. Regardless of whether it makes a difference to the effectiveness of the covid-19 vaccine, protecting sleep is a powerful way to protect quality of life - and it might have additional benefits for protecting us in the fight against coronavirus.
Dr Sophie Bostock has always been intrigued by why what makes us feel good. Following a degree in medicine at Nottingham University, she went on to complete a PhD in Health Psychology at University College London (UCL), investigating why happiness protects against heart disease, and how to improve wellbeing at work.