The Science Behind How Sleep Affects Your Immune System

Have you ever wondered how sleep affects your immune system? Let's dive into the science behind this crucial relationship.

How does sleep affects the immune system?

Sleep plays a crucial role in maintaining a healthy and well-functioning immune system. The immune system is a complex network of cells, tissues, and organs that work together to protect the body against pathogens, infections, and diseases. Sleep affects various immune parameters, is associated with a reduced infection risk, and can improve infection outcome and vaccination responses.² Much of the human evidence is observational, so it shows associations rather than proving that sleep alone prevents infection.

One way sleep is linked to the immune system is through the rhythm of cytokines, which are signaling molecules involved in the immune response. Studies of the normal sleep-wake cycle show that the production of pro-inflammatory cytokines peaks during early nighttime sleep, whereas anti-inflammatory cytokine activity peaks during daytime wakefulness.¹ Because sleep and the body clock both influence these rhythms, it is difficult to separate the effect of sleep itself from that of the circadian system.¹

Pro-inflammatory cytokine production peaks during early nighttime sleep.

Sleep also affects immune cells. Numbers of undifferentiated naive T cells peak during early nighttime sleep, and sleep appears to facilitate the movement of T cells and their possible redistribution to lymph nodes, whereas circulating cytotoxic natural killer (NK) cells peak during daytime wakefulness.¹ In experiments, sleep on the night after hepatitis A vaccination was followed by a strong and persistent increase in antigen-specific T helper cells and antibody levels, which suggests a role for sleep in forming immunological memory.¹

Furthermore, short sleep has been linked to a weaker immune response to vaccines. A 2023 meta-analysis in healthy adults found that objectively measured short sleep around the time of vaccination was associated with a lower antibody response (pooled effect size 0.79, 95% CI 0.40 to 1.18; 304 participants), whereas self-reported short sleep (under 6 hours per night) did not reach the authors' threshold for statistical significance.³ In men the pooled effect size was 0.93 (95% CI 0.54 to 1.33); in women it was not significant.³ In an observational study of 125 healthy adults given a hepatitis B vaccine series, shorter actigraphy-measured sleep was associated with a lower secondary antibody response and a lower likelihood of being clinically protected at the end of the series.⁴ These studies show associations; the amount of sleep needed to protect the response has not been defined.³

In addition to its direct effects on immune function, sleep also plays a role in regulating the body's stress response. A meta-analysis of more than 300 studies found that chronic stressors were associated with suppression of both cellular and humoral measures of immune function.⁵ During slow-wave sleep, cortisol levels are low, as part of a hormonal pattern (with high growth hormone and prolactin) that is associated with the role of sleep in forming immunological memory.¹

Sleep and inflammation are also linked. In a pooled analysis of 72 studies (more than 50,000 people), sleep disturbance was associated with higher levels of C-reactive protein (CRP) and interleukin-6 (IL-6), and shorter sleep duration (but not the extreme of short sleep) with higher CRP but not IL-6, while experimental sleep deprivation or restriction was not associated with CRP, IL-6 or tumor necrosis factor alpha.⁶ A review of the sleep-immune literature notes that prolonged sleep deficiency is associated with low-grade systemic inflammation and with diseases that have an inflammatory component, such as diabetes, atherosclerosis and neurodegeneration.² These are associations; they do not show that poor sleep causes these diseases.

What happens when you don't get enough sleep?

Short sleep has been linked to a greater risk of catching a cold. In a study of 164 healthy adults who were exposed to a cold virus, people who slept under 5 hours (odds ratio 4.50, 95% CI 1.08 to 18.69) or 5 to 6 hours (odds ratio 4.24, 95% CI 1.08 to 16.71) per night, measured by wrist actigraphy in the week before exposure, were more likely to develop a clinical cold than those who slept more than 7 hours.⁷ The confidence intervals are wide, so the size of the effect is uncertain, and an observational study like this cannot show that sleep alone decides whether someone gets sick.

This article does not claim that sleep supplements improve immune function. Melatonin, which is found in some sleep supplements, can cause fatigue and affect mood and psychomotor and cognitive performance in some people, and may interact with blood pressure medicines.⁸ Other ingredients can also affect how medicines work, so check the label. Ask a pharmacist or doctor first if you take other medicines, are pregnant or breastfeeding, or are giving a supplement to a child, and do not drive or operate machinery after taking a sleep supplement until you know how it affects you. Products some people use for sleep:

Sleep Formula

Sleep Strips (under tongue)

How much sleep do adults need?

The National Sleep Foundation recommends 7 to 9 hours of sleep per night for young adults and adults, and 7 to 8 hours for older adults.⁹ Needs vary between people. The studies above show associations between short sleep and weaker immune responses, but they do not define how much sleep is needed to protect against infection.³

What are some tips for improving sleep quality?

To improve your sleep quality, there are a few things one can do:

1. Try establishing a bedtime routine. Establishing a bedtime routine can be immensely beneficial in improving sleep quality and quantity. By preparing the body and mind for sleep, a routine signals to the brain that it is time to wind down and relax, helping to reduce stress and anxiety. A consistent bedtime routine can also help regulate the body's circadian rhythm, leading to a more regular sleep-wake cycle. A good bedtime routine might include activities such as reading a book, taking a warm bath, or practicing relaxation techniques like meditation or deep breathing. Establishing a routine that works for you may help you get better quality rest.
2. Create a comfortable sleep environment. Creating a comfortable sleep environment is essential to improve your sleep quality. A comfortable sleep environment should be calm, cool and quiet. To achieve this, you can try minimizing noise, keeping the bedroom well ventilated and installing curtains or blinds to block out light. Choosing comfortable bedding and pillows is also essential to create a comfortable sleep environment. Additionally, it would be best if you made sure the temperature is cool enough to support a comfortable sleep. A comfortable sleep environment is crucial to ensuring you get enough rest to face the next day energized.
3. Avoid caffeine near bed time. Avoiding caffeine before bedtime can significantly improve your sleep quality. Caffeine is known to stimulate the central nervous system, keeping you alert and awake. If you consume caffeine before bed, it will take longer for you to fall asleep, and you may find yourself waking up more frequently throughout the night. In a trial, 400 mg of caffeine taken even 6 hours before habitual bedtime reduced total sleep time, so a common recommendation is to avoid caffeine for at least 6 hours before bedtime.¹⁰ Choosing caffeine-free alternatives such as herbal tea or water can help promote relaxation and better sleep.
4. Limit screens and stimulating activities before bed. In an experiment, people who read on a light-emitting device before bed took longer to fall asleep, had reduced melatonin secretion, later circadian timing and reduced next-morning alertness than when they read a printed book.¹¹ Stimulating or emotionally charged material may also keep your mind alert. Opting for relaxing activities instead, such as meditation or listening to calming music, may help create an environment that promotes restful sleep.

Prioritizing sleep is a proactive way to support your body's natural defense system. Good sleep habits come first. If you are considering a sleep supplement, such as Sleep Formula, read the label and talk with your pharmacist or doctor first, especially if you take other medicines, are pregnant or breastfeeding, or drive or operate machinery. A supplement is not a treatment for insomnia. If you have trouble sleeping most nights, loud snoring or daytime sleepiness, or sleep problems that keep happening, talk to a doctor; cognitive behavioral therapy for insomnia (CBT-I) is recommended as the first treatment for chronic insomnia.¹² 

By understanding the research on sleep and immune function, you can make informed choices to prioritize rest. Sleep is one of several factors that influence immune function, and it does not replace vaccination or medical care.

In summary, research links sleep with immune function, including cytokine rhythms, T-cell behavior, antibody responses to vaccines and markers of inflammation.^1,2 Much of the human evidence is observational, so it shows associations rather than proving that more sleep prevents illness. Regular sleep habits and enough sleep for your age are reasonable goals for general health.

References:

1. Besedovsky L, et al. Pflugers Arch. 2012;463(1):121-37. PubMed · DOI
2. Besedovsky L, et al. Physiol Rev. 2019;99(3):1325-1380. PubMed · DOI
3. Spiegel K, et al. Curr Biol. 2023;33(5):998-1005.e2. PubMed · DOI
4. Prather AA, et al. Sleep. 2012;35(8):1063-9. PubMed · DOI
5. Segerstrom SC, et al. Psychol Bull. 2004;130(4):601-30. PubMed · DOI
6. Irwin MR, et al. Biol Psychiatry. 2016;80(1):40-52. PubMed · DOI
7. Prather AA, et al. Sleep. 2015;38(9):1353-9. PubMed · DOI
8. Foley HM, et al. Complement Ther Med. 2019;42:65-81. PubMed · DOI
9. Hirshkowitz M, et al. Sleep Health. 2015;1(4):233-243. PubMed · DOI
10. Drake C, et al. J Clin Sleep Med. 2013;9(11):1195-200. PubMed · DOI
11. Chang AM, et al. Proc Natl Acad Sci U S A. 2015;112(4):1232-7. PubMed · DOI
12. Qaseem A, et al. Ann Intern Med. 2016;165(2):125-33. PubMed · DOI

This article is general information and is not medical advice. Dietary supplements are not intended to diagnose, treat, cure or prevent any disease. Talk to a doctor or pharmacist before starting a supplement, especially if you are pregnant or breastfeeding, have a medical condition or take medicines.