You've probably heard about how significant a role stress is believed to play in the development of illness and disease. The immune system, the body's defense system against infection and disease, is weakened and undermined by the physical effects of stress. The result is an increased risk for all types of illness. If you've ever come down with a cold or the flu after a particularly stressful period -- think exam-time or a family crisis -- then you've experienced this firsthand. The long-term effects of stress on the immune system include a heightened risk of serious disease.
Here's some sobering and important news: New research indicates that lack of sleep can be as damaging to the immune system as stress.
An international team of scientists from the Netherlands and the United Kingdom examined the immune response of 15 healthy men under conditions of highly regulated sleep and also under conditions of severe sleep deprivation. What they discovered was a significant disruption to the normal functioning of immune system white blood cells when the men were deprived of sleep. This cellular response to sleep deprivation "directly mirrored the body's stress response," according to a member of the research team and the study's lead author.
The 15 adult men, all of whom were under the age of 30 and in good health, were put on a highly-regimented sleep schedule for one full week. This included a nightly eight hours of sleep, and early-in-the-day exposure to sunlight -- 15 minutes of outdoor light exposure within 90 minutes of waking. During the last three days of the week, the men consumed no caffeine or alcohol, and they were prohibited from using any medication. This schedule helped to diminish any sleep deprivation that existed among the men and also to strengthen and regulate their circadian clocks.
After this sleeping week was completed, researchers measured and analyzed the numbers and functioning levels of the men's white blood cells. (White blood cells are one of the major cell types of the immune system.) The men were then subjected to a period of extreme sleep deprivation, staying awake for 29 straight hours without any sleep. Researchers again measured white blood cell activity after this period of prolonged sleep deprivation. They found that white blood cell counts rose significantly after sleep deprivation, particularly a type of white blood cell called granulocytes, one of the most common and important cells in the immune system. This spike in white cell count from sleep deprivation essentially mimicked the physical response the body undergoes during episodes of stress, when white cell counts surge in a "fight-or-flight" type of stress response.
There's a substantial body of evidence that stress weakens the immune system and makes us vulnerable to infection and disease -- everything from a sniffly nose or a cough and cold to serious and chronic illnesses such as cancer and heart disease. This relationship between psychological distress and physical illness is at the heart of the mind-body relationship that has received so much attention -- deservedly so -- in recent decades.
We've also known for some time of a relationship between sleep and a healthy immune system, and the damage that a lack of sleep can have. Previous research has established links between sleep deprivation and immune function:
- There's a significant body of research to show that immune function is tied closely to the body's 24-hour circadian clock. When sleep is deprived, this cycle is weakened and disrupted, and the immune system suffers.
- Many studies -- including the current one -- use exposure to extreme sleep deprivation to identify and analyze sleep-related disruptions to the immune system. But this research showed that even mild sleep deprivation was associated with deterioration in immune function.
- The impact of even a few nights of disrupted sleep on immune function can linger even after sleep levels have improved. This study found disruptions to immune function after just two nights of full sleep deprivation, or four nights of partial sleep deprivation. Researchers continued to monitor immune function during a sleep recovery period. They found that while some cells involved in immune activity returned to their normal levels after several nights of recovery sleep, other immune system cells did not.
This new study, by linking the physical response of sleep deprivation to that of stress, brings additional clarity and also urgency to our understanding of just how dangerous sleep deprivation can be to our body's most basic defense system.
We continue to hear a lot about how important it is to manage stress in order to live a healthy life. Turns out, it is every bit as important to manage sleep.
Michael J. Breus, PhD
The Sleep Doctor™
Everything you do, you do better with a good night's sleep™
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