Sleep and immunity: does poor sleep really raise your risk of infection?

Studies show that people who regularly sleep too little have more upper respiratory tract infections, and that restricting sleep can affect the activity of immune cells, inflammation, and the body's response to vaccination.

That does not mean one bad night will give you a cold. What matters above all is regular sleep deprivation.

In autumn there is a great deal of talk about vitamin D, zinc, vitamin C and "immunity" supplements. Far less attention goes to what we do every night.

Yet sleep is one of the basic things that keep the immune system working properly.

What does sleep have to do with immunity?

Sleep is not a period when the body simply switches off.

Hormonal, metabolic and immune changes happen through the night. The activity of different immune cell populations shifts, as does cytokine release and the way the parts of the immune system communicate.

The relationship runs both ways. Sleep affects immunity, and an infection affects sleep. That is one reason why flu or a heavier cold makes us sleepier and more in need of rest.

Do people who sleep badly really get sick more often?

The available data point that way.

A systematic review published in 2021 found that shorter sleep was associated with roughly a 30% higher likelihood of upper respiratory tract infections.

That does not mean someone sleeping six hours will certainly fall ill, or that someone sleeping eight is fully protected.

The risk of infection also depends on contact with the pathogen, age, vaccination, coexisting conditions, diet, stress and many other factors. Sleep is one element of that picture.

How much should we sleep?

The requirement depends mainly on age.

These are population values, and individual needs can differ.

Time spent in bed is not the same as time asleep. If someone goes to bed at 23:00 and gets up at 6:00 but spends an hour turning from side to side, they are not sleeping seven hours.

Is six hours really too little?

For most adults, six hours on a regular basis is less than current recommendations.

The key word, though, is regularly.

One night given to work, travel or a night out is not the same as sleeping five or six hours every night for weeks. It is chronic sleep deprivation that is far more strongly linked to the body working poorly.

If you wake up tired despite seven or eight hours in bed, the cause usually lies elsewhere. I wrote about that in the piece on why you wake up tired despite 8 hours of sleep.

Sleep and inflammation

Chronic sleep restriction can also affect inflammatory processes.

Studies observe changes in cytokine release and in the activity of various parts of the immune response. This should not be read as a simple "weakened immunity".

It is more precise to say that lack of sleep can disturb the proper regulation of the immune and inflammatory response.

That is one more reason to treat sleep as part of preventive care, not merely as a way to feel less tired.

Sleep may matter for vaccination too

One of the more interesting areas of research is the relationship between sleep and the response to vaccination.

A meta-analysis published in 2023 found that, in studies where sleep was measured objectively, sleeping less than six hours was associated with a weaker antibody response after vaccination.

It does not mean a vaccine stops working if you slept badly the night before. It does show that sleep is one of the factors that can affect the quality of the body's immune response.

The practical takeaway is therefore not "you must sleep perfectly the night before your shot". It makes far more sense to look after your sleep regularly, before and after.

It is not only the number of hours

Two people can spend eight hours in bed and feel completely different in the morning.

Healthy sleep also involves:

• continuity,
• regularity,
• the time you fall asleep and wake up,
• the number of awakenings,
• how recovered you feel.

Regularity of the sleep-wake rhythm is drawing particular attention.

Large differences between weekdays and the weekend can produce what is known as social jet lag. So it is worth caring not only about how much we sleep, but also about a reasonably consistent wake-up time.

Can you catch up on a whole week at the weekend?

Longer sleep can partly reduce tiredness and help after a few short nights.

It does not mean, though, that five hours from Monday to Friday plus ten on Saturday and Sunday is equivalent to regular sleep through the week.

Large shifts in sleep timing can additionally disturb the circadian rhythm. Weekend catch-up sleep is an emergency measure rather than an ideal model of recovery.

Why can sleep get worse in autumn?

In autumn the days get shorter and exposure to natural light falls. Light is one of the most important signals setting the body clock, which I wrote about in the piece on how morning light affects sleep and energy.

At the same time September and October often mean going back to school or university, more work, and more screen time in the evening.

In practice it can turn out that we start sleeping less exactly during the infection season.

Phones before bed: do they really interfere?

Blue light is not the only problem. A phone can simply push back the moment you go to sleep.

One reel becomes ten, one episode becomes the next, and the last email turns into an extra hour of work.

If devices regularly take an hour of your sleep, cutting that single habit can matter far more than buying another supplement for sleep or "immunity".

What about caffeine?

Caffeine acts for a relatively long time. In some people even an afternoon coffee can make falling asleep harder or worsen sleep quality.

There is no single cut-off hour that suits everyone. If you have trouble falling asleep, it is worth checking whether moving your last coffee earlier helps. More on when caffeine helps and when it worsens energy.

Does alcohol help you sleep?

It can make you drowsy, but that is not the same as better sleep.

Alcohol can disturb sleep architecture and increase awakenings in the second half of the night. It should not be treated as a way to improve recovery. On how much fits within sensible limits, I wrote about a safe amount of alcohol.

How to look after sleep in autumn, realistically

You do not need an elaborate evening routine.

Is it worth sleeping more during an infection?

Yes, if your body clearly needs it.

Greater sleepiness during an acute infection is part of the physiological response to illness.

So there is no need to police exactly eight hours during a cold or flu. The extra rest can be a natural part of recovery.

In short

Sleep is no guarantee that you will not fall ill this autumn.

It is, however, one of the basic things that keep the immune system working properly.

Regular sleep deprivation is associated with a higher risk of infection, and research also points to its role in the immune response after vaccination.

So before reaching for yet another "immunity" supplement, and autumn offers no shortage of them, from ginger for immunity onwards, it is worth checking something far more basic:

how many hours do we actually sleep on most nights of the week?

Sometimes that is where the biggest room for improvement lies.

Frequently asked questions

Does lack of sleep really affect immunity?

Yes. Chronic sleep restriction can affect the activity of immune cells, cytokine release and inflammatory processes. One short night is a different matter from several weeks of five or six hours.

Does less than 7 hours of sleep raise the risk of infection?

Observational studies indicate that shorter sleep is associated with a higher risk of upper respiratory tract infections. In a 2021 systematic review this was roughly a 30% higher likelihood.

Will one sleepless night make me ill?

That cannot be claimed. The risk of infection depends on contact with the pathogen, age, vaccination and many other factors. Regular, chronic sleep deprivation matters far more than a single night.

How much should an adult sleep?

Most adults are advised to get at least 7 hours a night. That is a population value and individual needs differ. Time spent in bed is not the same as time asleep.

Can you catch up on lost sleep at the weekend?

Partly. Longer sleep reduces tiredness after a few short nights, but five hours on weekdays and ten at the weekend is not equivalent to regular sleep, and it shifts the circadian rhythm further.

Does sleep affect how well a vaccine works?

A 2023 meta-analysis found that, where sleep was measured objectively, sleeping under six hours was associated with a weaker antibody response. That argues for regular sleep before and after vaccination, not for one well-slept night.

Is it worth sleeping longer during an infection?

Yes. Greater sleepiness during an acute infection is part of the physiological response to illness, so the extra rest is a natural part of recovery.

References

1. Paruthi, S., Brooks, L.J., D'Ambrosio, C. et al. (2016). Recommended Amount of Sleep for Pediatric Populations: A Consensus Statement of the American Academy of Sleep Medicine. Journal of Clinical Sleep Medicine, 12(6), 785–786. doi:10.5664/jcsm.5866
2. Besedovsky, L., Lange, T. & Haack, M. (2019). The Sleep-Immune Crosstalk in Health and Disease. Physiological Reviews, 99(3), 1325–1380. doi:10.1152/physrev.00010.2018
3. Robinson, C.H., Albury, C., McCartney, D. et al. (2021). The relationship between duration and quality of sleep and upper respiratory tract infections: a systematic review. Family Practice, 38(6), 802–810. doi:10.1093/fampra/cmab033
4. Spiegel, K., Rey, A.E., Cheylus, A. et al. (2023). A meta-analysis of the associations between insufficient sleep duration and antibody response to vaccination. Current Biology, 33(5), 998–1005.e2. doi:10.1016/j.cub.2023.02.017
5. Feuth, T. (2024). Interactions between sleep, inflammation, immunity and infections: A narrative review. Immunity, Inflammation and Disease, 12(10), e70046. doi:10.1002/iid3.70046
6. Centers for Disease Control and Prevention (2024). About Sleep. https://www.cdc.gov/sleep/about/