Can too little sleep make you more susceptible to infections?

Too little sleep increases your chances of becoming ill from infections. This applies both to catching a disease more readily and to fighting it less effectively. The immune system needs sleep for two types of defence: the fast, general response and the more specific, longer-lasting response that also protects you after vaccinations. Both are disrupted by sleep deprivation.

A concrete example: people who sleep too little before or after a vaccination build up less protection. The vaccine then works less effectively. This has been studied in both epidemiological studies and laboratory research, and the association is confirmed in multiple studies.

Sleep deprivation also raises the level of inflammation-promoting substances in your blood. With short-term sleep loss this is temporary, but with chronic sleep deprivation a persistent, low-grade inflammation develops in the body. This smouldering inflammation is thought to contribute to conditions such as diabetes, cardiovascular disease and possibly neurodegenerative disorders, although the precise causal chain has not yet been fully mapped out.

More or better sleep appears to have the opposite effect: the immune system recovers and functions better. But the evidence for this is still limited; there are methodological challenges and open research questions remain. Concrete recommendations about how much extra sleep you need in order to be protected cannot yet be distilled from the studies.

Exact risk figures, such as 'x percent greater chance of catching a cold', are not provided in the available studies. But the direction is clear and is broadly supported: structurally too little sleep makes your immune system more vulnerable.