During the day your body uses a vast amount of energy even just to help you think and feel. Then there’s all the energy your body uses through physical activity.
Sleep is seen as a time to conserve energy and replenish these resources. While that’s partially true, you still use a considerable amount of energy at night. Instead of helping you navigate your daytime activities, however, you divert resources to keep your body and mind healthy.
Underpinning that process is the regulation of your immune system whereby new cells are created, old and dying or diseased cells are dispatched and toxins are cleared from your brain. This link between good quality sleep, or lack thereof, and the immune system can be observed in three core areas: responding to threat, managing illness, and prevention of illness.
How sleep helps your body respond to threats
T-cells are a central component of your adaptive immune system. When T-cells identify an infected cell they activate a sticky protein (integrin), which allows the T-cell to attach to the infected cell and kill it.
If you’ve not slept well your T-cells don’t produce as much integrin and it’s harder to stick to, and destroy, the infected cell. That’s because sleep disturbances and deprivation are interpreted physiologically as a threat, which activates the fight or flight response. Part of that response is the production of adrenaline and noradrenaline, both of which should, under normal circumstances, decrease during the night. It’s this adrenaline and noradrenaline that reduces the efficacy of integrin, making the immune system less effective.
How sleep manages illness
We often want to sleep more when we’re unwell. The reason for this is we need more energy for our immune systems to fight the illness, which is achieved by turning down activity in cells in the nervous system that would normally be keeping us awake.
Fever response – evidence that the immune system is hard at work fighting infection – also occurs at night. If you’re not sleeping well the ability to create an effective fever response is diminished, prolonging recovery.
Poor sleep also reduces your body’s capacity to distinguish between innate and foreign antigens in the body, which can result in a limited, or non-response. In extreme cases it could even trigger an autoimmune response whereby your immune system actually starts attacking healthy cells and tissue.
How sleep prevents illness
Several studies demonstrate links between sleep and the development of an infection. One study measured the amount an individual slept, on average, before giving them the rhinovirus (the common cold). The results showed that those who slept less than six hours were more likely to develop the cold compared to those that slept more.
Other studies have looked at the effectiveness of vaccinations, including Hepatitis A and B, in relation to sleep. Those who were deliberately sleep deprived showed a poorer uptake response compared to those allowed to sleep normally, at least in the short term.
Sleep helps make it less likely you’ll become ill and more likely you’ll recover quicker from illnesses you do succumb to. It even helps build up your immunity faster following a vaccination.
How to get the best sleep for your immune system
To reap the immunity-boosting benefits of sleep, you need to get the right amount of it. The science shows too much sleep can be as detrimental as not enough, so how much do you need? The acid test is how you feel in the morning. If an hour or so after waking you feel tired and sluggish, the likelihood is there’s a problem with the quality, quantity or timing of your sleep that needs further investigation.
Sleep is a natural process that can’t be forced. The more you try to sleep the more evasive it becomes. Routine is important, especially waking up around the same time, but the main rule to follow is very simple: go to bed when you’re sleepy! Do that and you’ll massively decrease the chances of lying there awake unable to nod off.
It may seem counterintuitive, but if you do find yourself in bed fully awake and unable to sleep, get up and out of bed. Otherwise you’ll just get frustrated, which only makes it harder to drift off. Try reading or listening to music, and only go back to bed when you feel sleepy.
Have a wind-down routine a couple of hours before bedtime. To avoid overstimulation (or hyperarousal as it’s technically referred to) don't check work emails or scroll through social media during this time.
One method that has proved particularly effective with the people I’ve helped is to write a to-do list. Include all the things you have to do the next day, and give yourself time to think about any worries and concerns. This unloads your day’s thoughts and concerns, preventing them running around your head as you rest it on your pillow.
Dr Jason Ellis is a professor of sleep science and director of the Northumbria Sleep Research Laboratory.