Sleep and the Immune System


Written by Alison Deshong

Reviewed by Dr. Michael Breus

Our Editorial Process

Table of Contents

Adequate sleep supports overall health in a number of ways, including keeping the immune system functioning at its best. Important immune processes occur during sleep, enhancing the body’s ability to fight off disease. 

People can be more susceptible to illness when they do not get enough sleep. Inadequate sleep affects the immune system’s ability to fight off infections. It can also lead to chronic inflammation, which can increase the risk of developing heart disease, cancer, and dementia.

We discuss how the immune system works, the impact on immunity when you do not get adequate sleep, and how you can get the sleep your immune system needs to function at its best.

Can Lack of Sleep Make You Sick?

Not getting enough sleep can increase the risk for infection and illness, because sleep loss disrupts the healthy functioning of the immune system. 

Adults typically need seven to nine hours of sleep per night, while children and teenagers need more. Around one third of adults in the United States do not get the sleep they need, in part due to daily stressors and lack of time. Sleep disorders like obstructive sleep apnea and insomnia can also cause people to get less sleep than they need. 

Insufficient sleep can lead to infection with contagious diseases. Sleep loss can make people more susceptible to catching a common cold. And getting less than seven hours of sleep can put people at almost three times the risk of becoming sick after exposure to a common respiratory virus. 

Sleep loss is also associated with chronic health conditions, including diabetes, heart disease, hypertension, and stroke. Both short-term and long-term lack of sleep can negatively affect the immune system.

How the Immune System Works

The primary role of the immune system is to help the body identify and destroy harmful invaders, called pathogens, such as bacteria, viruses, fungi, and toxins. A healthy immune system identifies these substances as foreign and mounts an immune response to attack and eliminate them. 

The immune response unfolds in various stages.

  • Physical Barriers: The immune system’s first defense is to prevent harmful substances from entering the body. Examples include the body’s skin, coughing reflex, and stomach acid, which can destroy sources of food poisoning. The layer of mucus that covers many organs also serves as a physical barrier against pathogens. 
  • General Immune Response: When the physical barriers are inadequate at keeping pathogens at bay, the body can quickly dispatch white blood cells. These cells rapidly engulf invading germs and eliminate them or kill infected cells.
  • Inflammation: If the infection escalates, the general response system can create inflammation and fever. This response alerts the other elements of the immune system that an infection has occurred and helps those cells access the site of infection.
  • Antibodies: As an infection progresses, the immune system may produce antibodies, proteins that can neutralize specific bacteria, viruses, or toxins. Antibodies allow the immune system to remember these pathogens and attack them more quickly in the future.

Both the physical barriers and general response system are inherited features, present at birth. Other tools of the immune system are acquired throughout life. The immune system develops more specific defense mechanisms through exposure to particular pathogens and through vaccinations.

How Does Sleep Affect the Immune System?

Sleep benefits the immune system, helping the body to recover from infections and disease and by preparing itself for any upcoming challenges. 

The immune system continuously produces cells to protect the body from pathogens. During sleep, some immune cells are redistributed, moving throughout the body. For example, infection-fighting cells move into the lymph nodes, a system of glands in various locations throughout the body that support the immune system.

Sleep is crucial to overcoming illnesses, but also in preventing them. Sleep helps the body prepare its defenses and boost our immune system – that’s why when we’re sick we tend to feel an increased urge to sleep.
Dr. Michael Breus

Hormonal changes also happen during sleep that promote a number of immune processes. Examples of immune processes influenced by hormones include inflammation and antibody development.

Inflammation in the body peaks during sleep. Nighttime inflammation prepares the body to fight sources of infection the following day. Antibody formation mostly occurs during deep sleep

Effects of Sleep Loss on the Immune System

Because sleep is vital to the proper functioning of the immune system, sleep deprivation can put people at increased risk of getting sick.

  • Reduced White Blood Cell Activity: Certain white blood cells help the body to kill tumor cells. Even one night of only four hours of sleep can reduce the activity of these cells to about 70%. 
  • Fewer White Blood Cells in Lymph Nodes: Short-term and long-term sleep loss can reduce the number of white blood cells in the lymph nodes, reducing the fighting power of the immune system against pathogens.
  • Increased Inflammatory Cells: Levels of inflammatory cells can increase with long-term sleep loss and even after just one night of insufficient sleep. Increased inflammation can lead to the development of heart disease and metabolic disorders like diabetes. 
  • Lower Antibody Production: Sleep loss can result in a reduced response to vaccination. People who get the recommended hours of sleep after a vaccination can generate higher levels of antibodies than people with restricted sleep. 

How Does Fighting Illness Affect Sleep? 

People can experience changes to their sleep during an infection. Being sick prompts the immune system to send chemical signals to the brain that can then alter sleep in a variety of ways. 

  • Vivid Dreaming: People sometimes experience strange, vivid dreams when sick with a fever. Fevers may occur when the body is fighting off an infectious disease. For instance, people who have been infected with COVID-19 have reported more frequent nightmares, although other aspects of the infection could account for this. 
  • Altered Sleep Stages: During an infection, the immune system sends signals to the brain that can alter sleep stages. People experiencing an infection often spend less time in rapid eye movement (REM) sleep than healthy people. 
  • Changes to Sleep-Wake Cycle: Circadian rhythms, which work to make people wakeful during the day and sleepy at night, can shift as a result of illness. The immune system’s inflammatory response may be the culprit in causing disruptions to this sleep-wake cycle.
  • Pain-Related Sleep Changes: When illness causes pain, the pain itself can make it more difficult to fall asleep, may increase the chances that a person will awaken during sleep, and could cause them to spend less time in deep sleep and REM sleep. 

How to Improve Sleep to Support Your Immune System

Quality and quantity of sleep are important for optimal immune function, so taking steps to ensure sufficient sleep can pay off in good health. Some lifestyle habits that support better sleep also independently support the immune system. 

  • Practice Good Sleep Hygiene: Good sleep habits are also referred to as sleep hygiene. Going to bed and waking up at the same time every day, creating a comfortable sleep environment, storing your phone away from your bed, and avoiding alcohol and caffeine close to bedtime are habits that can support healthy sleep. 
  • Treat Sleep Disorders: Sleep disorders can cause poorer sleep. Talk to your doctor if you suspect that you have symptoms of a sleep disorder, like trouble falling asleep, difficulty staying asleep, gasping for air or snoring during sleep, or uncontrollable leg movement at night.
  • Exercise: Incorporating regular exercise into your daily routine has a number of health benefits. Physical activity during the day can also help you sleep better at night. Exercise may also reduce your chances of developing an infection or chronic disease. 
  • Incorporate Relaxation Practices: Managing stress with relaxation techniques can help you cope with stress and wind down before falling asleep. Practices like mindfulness meditation could benefit the human immune system as well.

About The Author

Alison Deshong

Staff Writer, Product Testing Team

Alison is a health writer with ample experience reading and interpreting academic, peer-reviewed research. Based in San Diego, she is published in the journal PLOS Genetics and the Journal of Biological Chemistry and has been a copywriter for SmartBug media. With a master’s degree in biochemistry from the University of California, Davis, she has nearly a decade of academic research experience in life sciences. She enjoys helping people cut through the noise to understand the bigger picture about sleep and health. Alison likes to stay active with rock climbing, hiking, and walking her dog.

  • POSITION: Stomach Sleeper
  • TEMPERATURE: Neutral Sleeper

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