Sleep and the Immune System: Why Short Sleep Leaves You Run Down
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Sleep and the immune system are closely connected. Most of us know we're more likely to come down with something after a run of late nights, and research backs that up. This guide covers how sleep supports your immune system, what studies found about short sleep and catching a cold, the link between sleep and vaccines, why you feel so sleepy when you're sick, and practical ways to protect your sleep when it matters most.
The short answer: sleep supports your immune system, and consistently short sleep weakens it. In one well-known study, people who slept less than six hours a night were over four times more likely to develop a cold after being exposed to the virus than those who slept more than seven. Short sleep around the time of a vaccination has also been linked to a weaker antibody response. Long-term sleep loss is linked to low-grade inflammation. Getting enough regular sleep is one of the simplest things you can do for your health.
How sleep supports your immune system
A large 2019 review by Luciana Besedovsky, Tanja Lange and Monika Haack looked at decades of research on how sleep and the immune system interact. It concluded that sleep affects a range of immune measures, is associated with a lower risk of infection, and can improve how well you recover from infection and respond to vaccines (source).
Some of the ways this seems to work:
- Hormones. During sleep, the body's hormone pattern shifts into one that supports immune activity.
- Immune memory. Deep sleep appears to play a part in helping the immune system "remember" a germ or vaccine, so it can respond faster next time.
- Keeping inflammation in check. Prolonged short sleep or disturbed sleep can lead to ongoing, low-grade inflammation throughout the body.
Better Health Channel notes that long-term sleep deprivation can make you more susceptible to infections and reduce your immune response to vaccination (source).
Short sleep and catching a cold
One of the clearest studies on this was published in 2015. Researchers measured the sleep of 164 healthy adults with a wrist device for a week, then gave them nasal drops containing a common cold virus and watched who got sick over the next five days (source).
| Average sleep before exposure | Risk of developing a cold, compared with more than 7 hours |
|---|---|
| Less than 5 hours | About 4.5 times higher |
| 5 to 6 hours | About 4.2 times higher |
| 6 to 7 hours | About 1.7 times higher (not statistically significant) |
| More than 7 hours | Comparison group |
The link held even after the researchers allowed for age, body weight, stress, existing antibodies and health habits. Interestingly, broken sleep on its own wasn't linked to catching a cold; total sleep time was what mattered.
This was one study with a modest sample, so the exact numbers shouldn't be taken too literally. But the direction is clear, and it fits the wider research. If you're regularly getting six hours or less, see is 6 hours of sleep enough.
Sleep and vaccines
A 2023 meta-analysis in Current Biology by Spiegel and colleagues pooled studies on sleep in the days around vaccination and antibody responses in healthy adults. When sleep was measured objectively, short sleep (under six hours a night) was linked to a clearly weaker antibody response. When people simply reported their own sleep, the link was weaker and didn't reach statistical significance. The effect was stronger in men than in women, and the authors called for larger studies to work out how much sleep is needed and when it matters most.
The practical takeaway is simple: if you have a vaccination coming up, it's a good week to protect your sleep. If you're unsure about timing a vaccine, talk to your GP or pharmacist rather than putting it off.
Why you feel so sleepy when you're sick
The connection runs both ways. When you're fighting an infection, your immune system changes your sleep. The 2019 review describes the tiredness and sleepiness that come with illness as part of the body's response, encouraging a less active state that likely helps you recover by conserving energy.
So if you're unwell, extra rest is normal. Listen to it. For practical tips, see how to sleep with a cold or flu.
How to protect your sleep (and your immune system)
You can't sleep your way out of every bug, but these habits help you get enough sleep regularly:
- Aim for 7 to 9 hours. That's what the Sleep Health Foundation says most adults need to feel properly refreshed. See how much sleep do I need.
- Keep a regular wake-up time, including weekends, so your body clock stays steady.
- Protect sleep in high-risk weeks: around vaccinations, during cold and flu season, and before travel.
- Watch late caffeine and alcohol, both of which can cut into sleep quality.
- Don't rely on weekend catch-ups. A lie-in may help a little, but regular nights of enough sleep are the better goal. See can you catch up on sleep.
- Use the basics. A cool, dark, quiet bedroom and a wind-down routine. See the sleep hygiene checklist.
When to see your GP
See your GP if you keep getting sick, if infections are slow to clear, or if you're struggling to sleep enough most nights. Ongoing poor sleep can have treatable causes such as insomnia or sleep apnoea. Sleep supports your immune system, but it's not a substitute for vaccination or medical care. This guide is general information, not medical advice.
Where the Sovune Nudge fits
We make the Sovune Nudge, a silent alarm wristband, so we're not neutral. It has no effect on your immune system, but it can help you keep a steady wake-up time without disturbing anyone else in the house.
- Silent. No speaker and no sound, so a sick partner or child can keep sleeping when your alarm goes off.
- Wakes you with vibration on your wrist, starting as a gentle tap and building through three intensity levels.
- Set on the band itself. No app or phone needed, so your phone can stay out of the bedroom.
- Up to 14 days of nightly use per charge, rechargeable via USB.
It comes with a 30-day money-back guarantee.
Quick answers
Does lack of sleep make you sick? It doesn't cause illness on its own, but short sleep is linked to a higher chance of catching a cold after exposure to the virus.
How much sleep do I need to support my immune system? Most adults need 7 to 9 hours. In one study, people sleeping more than seven hours were least likely to catch a cold.
Should I sleep more when I'm sick? Yes, rest when you can. Sleepiness during illness is part of how your body responds to infection.
Does sleep affect how well a vaccine works? Studies suggest short sleep around vaccination is linked to a weaker antibody response, so it's worth protecting your sleep that week.
For every type of silent alarm compared, see our complete guide to vibrating alarms in Australia.