The link between lack of sleep and the immune system is stronger than many people realize. In a study where researchers exposed healthy adults to a cold virus, people who slept less than six hours a night were about four times more likely to get sick than those who slept more than seven. Short sleep has also been linked with weaker responses to vaccines. As cold and flu season approaches, sleep is one of the simplest ways to support your defenses.
Lack of sleep and your immune system: Quick Answer
- People sleeping under 6 hours were about 4 times more likely to catch a cold after virus exposure.
- Short sleep was linked with weaker antibody responses to hepatitis B and flu vaccines.
- Sleep and the immune system communicate in both directions.
- Aim for 7 to 9 hours on a consistent schedule, especially around vaccinations.
How Are Sleep and the Immune System Connected?
Sleep and immunity talk to each other constantly. During deep sleep, the body releases growth hormone and shifts toward immune-supporting signals, while stress hormones like cortisol dip. Immune cells redistribute and appear to form stronger memories of germs they have encountered. When you get sick, immune molecules in turn make you sleepier, encouraging rest (Besedovsky et al., Physiol Rev, 2019).
What Does the Research Show?
1. Short sleepers caught more colds
Researchers measured the sleep of 164 healthy adults with wrist monitors for a week, then gave them nasal drops containing a cold virus and monitored them in quarantine. People who slept less than six hours a night were about 4.2 times more likely to develop a cold than those sleeping more than seven hours, after accounting for age, stress and other factors (Prather et al., Sleep, 2015).
2. Poor sleep weakened vaccine responses
In a study of adults receiving the hepatitis B vaccine, those who averaged fewer than six hours of sleep were far less likely to be protected six months later than those who slept more than seven hours (Prather et al., Sleep, 2012). An earlier study found that healthy young men restricted to four hours of sleep for several nights produced less than half the antibody response to a flu vaccine compared with rested men (Spiegel et al., JAMA, 2002).
What Are Researchers Exploring Next?
Most studies are observational or short-term. It is hard to know exactly how much extra sleep protects a given person, and immune responses vary widely. Sleep is one of many factors, alongside vaccination, hand hygiene, nutrition, stress and exercise.
5 Ways to Support Your Immune System With Sleep
- Aim for seven to nine hours. Protect your sleep especially during cold and flu season.
- Keep a steady schedule. Consistent bed and wake times strengthen your body clock. See sleep schedule consistency.
- Prioritize sleep around vaccines. A few good nights before and after may support a stronger response.
- Calm your nervous system at night. Try a few minutes of cyclic sighing before bed.
- Rest when sick. Extra sleep during illness helps your body focus on recovery.
Sleep affects more than immunity; it influences hormones too, as we cover in sleep and testosterone. Want to know where sleep ranks among your body’s signals? Take the free Signal Map quiz.
Frequently Asked Questions
Does lack of sleep weaken your immune system?
Yes, research shows it can. In one study, people who slept less than six hours a night were about four times more likely to catch a cold after being exposed to a virus than those who slept more than seven hours.
How much sleep do you need for a healthy immune system?
Most adults need seven to nine hours. Studies of colds and vaccines suggest that regularly sleeping fewer than six hours is linked with weaker immune defenses.
Should I sleep more when I’m sick?
Rest helps. During infection, the immune system releases signals that increase sleepiness, and sleep appears to support the immune response. Listen to your body and prioritize rest when you are unwell.
Want to go deeper? The 14-Night Deep Sleep Rebuild is a step-by-step program for rebuilding your sleep signal. See the program →
Sources
- Prather AA, et al. Behaviorally assessed sleep and susceptibility to the common cold. Sleep. 2015;38(9):1353-1359. doi:10.5665/sleep.4968
- Prather AA, et al. Sleep and antibody response to hepatitis B vaccination. Sleep. 2012;35(8):1063-1069. doi:10.5665/sleep.1990
- Spiegel K, Sheridan JF, Van Cauter E. Effect of sleep deprivation on response to immunization. JAMA. 2002;288(12):1471-1472. doi:10.1001/jama.288.12.1471-a
- Besedovsky L, Lange T, Haack M. The sleep-immune crosstalk in health and disease. Physiol Rev. 2019;99(3):1325-1380. doi:10.1152/physrev.00010.2018
This article is for education only and is not medical advice. Talk with your healthcare professional before changing your health routine.