Most of us catch a few colds in any given year. Perhaps a flu now and again. And the occasional stomach bug. Not a big deal for the majority of people. But these minor illnesses do materially impact our performance throughout the year.
It’s useful to know, then, that getting sufficient sleep may reduce your susceptibility to these types of infections. In the midst of a global viral pandemic, this is particularly pertinent.
In 2018, nearly 40% of work sickness absence was attributable to minor illnesses, such as colds, flu, and stomach bugs. If we’re unable to show up for work, we’re unable to show up (fully, at least) for all the other things we want to do. It’s uncontroversial to say that life would be better if we got fewer infections. But can we do anything to influence this?
Eating a nutrient-dense diet and doing more exercise are undoubtedly beneficial, but it also appears that sleep may play a crucial role in bolstering our defences against infections.
In 2015, researchers in the United States investigated whether sleep duration had an effect on susceptibility to the common cold. They took 164 healthy men and women and tracked their sleep for a week using a wristwatch device. The participants were then quarantined and had a dose of rhinovirus (the common cold virus) literally sprayed into their nostrils (nice!). During the next 5 days they were closely monitored for the development of a clinical cold.
The infection rate in the people sleeping less than 5 hours a night was 45%. This went down to 30% in the people sleeping 5-6 hours a night. And dropped to only 17% in the people getting more than 7 hours a night.
Now, this doesn’t prove causation. The study wasn’t designed to do that. But it does show that longer sleep duration predicts lower susceptibility to infection from a cold virus, even when many other factors that are known to impact the immune system – such as BMI, physical activity, and alcohol consumption – are taken into account.
The consensus nightly sleep recommendation for adults is 7-9 hours. One third of the UK population is getting by on only 5-6 hours. This has many deleterious effects on health, and an increased risk of viral infection may be one of them. Getting sufficient sleep, therefore, is crucial. Perhaps now more than ever.