What does sleep deprivation do to your immune system?
Sleep deprivation demonstrably weakens your immune system: sleeping fewer than six hours significantly increases your infection risk and impairs your immune cells. Make sure to structurally get seven hours or more, because a single recovery night is not enough to repair the damage.
People who sleep fewer than 5 hours per night are more than four times as likely to catch a cold as people who sleep seven hours or more. Even sleeping between five and six hours still carries a similarly elevated risk. Only above six hours does that extra risk disappear. This has not only been found in population studies: in a controlled experiment, people were deliberately exposed to a cold virus, after which sleep was objectively measured with a wrist-worn tracker. The effect is therefore not an artifact of self-reporting.
Sleep deprivation also increases the amount of inflammatory substances in the blood. After partial sleep restriction, even just four hours per night for a working week, elevated levels of these substances are measurable in the blood and visible in the activity of white blood cells. One recovery night is not enough to undo those changes. This means that a sleep deficit you accumulate on Friday cannot be resolved with a single long Saturday night.
Both the rapid, innate immune defense and the trained branch of the immune system become impaired. Specific cells that normally clear viruses and bacteria divide less frequently and work less efficiently. At the same time, pro-inflammatory signaling pathways become more active. The body thus ends up in what amounts to a permanent, mild state of alert that does more harm than good.
Sleeping well also works in the other direction: it demonstrably improves the response to vaccinations and the defense against viral infections. Sleep is therefore not a passive rest period for the immune system, but an active process in which immune cells are produced and regulated.
Over the longer term, chronic sleep deprivation is linked in large population studies to a higher risk of cardiovascular disease, cancer, and brain diseases. That association likely runs partly through persistent low-grade inflammation. For each individual disease, a causal relationship has not yet been proven; the researchers themselves also identify this as a gap in knowledge. There are also preliminary indications that prolonged insufficient sleep accelerates biological aging at the cellular level and increases the risk of depression, but the evidence is currently too limited to make definitive statements.
The evidence for infection risk rests on a controlled experiment involving exposure to a cold virus and on multiple reviews that confirm this; for this specific effect, the evidence is relatively strong. The evidence for inflammation and immune disruption comes from multiple reviews of both experimental and population studies. For long-term consequences such as cancer and brain diseases, the evidence consists of associations in large population studies without proven causality per disease; the researchers themselves emphasize methodological limitations. The evidence for cellular aging and depression is the thinnest and not yet sufficiently substantiated for firm conclusions.
Does too little sleep weaken your immune system?
Yes, too little sleep demonstrably weakens your immune system and increases the risk of infections and chronic inflammatory conditions. Seven to nine hours of sleep is the most commonly cited guideline, and vaccinations also work better when you are well rested.
What does chronic sleep deprivation do to your inflammation in the long run?
Chronic sleep deprivation demonstrably raises inflammatory markers in your blood and is linked to diseases such as cardiovascular disease and dementia; getting enough sleep is therefore one of the most concrete things you can do yourself to limit chronic inflammation.
Does stress really lower my immune defences?
Prolonged stress measurably lowers your immune defences and even weakens the effectiveness of vaccines. Short-term stress, by contrast, is harmless or temporarily beneficial for your immune system.
Can too little sleep make you more susceptible to infections?
Too little sleep demonstrably makes your immune system more vulnerable, including to infections and vaccinations. Make sure you get sufficient sleep, even though the exact numbers and thresholds are not yet precisely known.
Does cold showering boost your immune system?
Cold showering produces measurable stimulation of the immune system, but whether it actually makes you less likely to fall ill has not been proven. Until better research is available, there is no harm in doing it if you enjoy it, but do not count on it as protection against infections.
What does alcohol do to your immune system?
Heavy or prolonged alcohol use clearly weakens your immune system and increases the risk of serious infections and liver disease. With moderate use the picture is mixed and too poorly understood to act on in practice.