Why Is Inflammation Worse at Night?


Written by Dr. Michael Breus

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If you pay attention to health issues, you probably hear a lot about inflammation. Chronic inflammation has gotten a lot of attention in recent years as a major contributor to illness and disease.

But how much do you know about the relationship between inflammation and sleep? That relationship brings together two complex and fundamental of the body’s systems — the immune system and our need for sleep. Keeping inflammation in check has big ramifications for our health. Sleeping well may be one way we can guard against the unhealthful inflammation that’s associated with chronic diseases from cancer and heart disease to autoimmune disorders such as rheumatoid arthritis and others.

What Is Inflammation?

In talking with my patients, I realize that while most of them understand that excessive inflammation can be harmful, many don’t have a strong understanding of what inflammation is, or what it does. Inflammation is a natural, protective biological response from the immune system to fight off harmful foreign pathogens — bacteria, viruses, toxins — that cause illness and disease, and to help the body heal from injury. The symptoms of acute inflammation, including swelling and redness, fever and chills, pain and stiffness, and fatigue, are signs the body’s immune system is in “fight mode,” working hard to neutralize a threat.

Problems with inflammation occur when this natural, protective response happens too often, or at the wrong times. Autoimmune diseases occur as a result of the body triggering an inflammatory response when there is no foreign threat present. Instead, the immune system’s pathogen-fighting cells attack the body’s own healthy cells and tissues. Multiple sclerosis, rheumatoid arthritis, and lupus are examples of autoimmune conditions that develop in part from an excessive, misdirected inflammatory response.

Chronic inflammation is also linked to the development of heart disease, stroke, diabetes and cancer—the major chronic and life-threatening diseases of our time. With chronic inflammation, the body’s immune system is in perpetual fight mode, activating disease-fighting cells that have no external threat to fend off. Over time, these fighter cells can attack, wear down, and cause damage to healthy cells, tissues, organs, and systems throughout the body, leading to chronic illness.

Sleep, Inflammation, and Bio Rhythms

In talking about sleep and the immune system, we’re tackling two of the most complicated processes of the human body. For all our scientific inquiry to sleep, there’s a tremendous amount we don’t know. Though it’s clear we need sleep to survive, scientists still don’t know why we sleep. The human immune system is tremendously complex, and scientists are still working to de-code its operations, to understand how it works—and why things go wrong.

One thing we do know? Sleep, immune function, and inflammation share a common regulator. Our sleep is regulated by circadian rhythms, which drive hormones and other physiological changes that cause us to move back and forth along a continuum of sleep and wakefulness throughout the 24-hour day. Those daily sleep-wake cycles we move through without much thought? Our circadian rhythms are working behind the scenes to keep us on schedule. When circadian rhythms are out of sync, so is sleep.

Circadian rhythms also regulate our immune system, and with it, our levels of inflammation. When circadian rhythms are disrupted, so is normal immune function. We’re more prone to unhealthful inflammation, and more at risk for diseases, including metabolic disease, cancer, and heart disease.

One way to help keep circadian rhythms in sync is to maintain a consistent sleep routine. Our bio rhythms thrive on consistency. Going to bed at the same time and waking at the same time every day reinforces the healthy circadian rhythms that govern both our sleep and our immune function, including inflammation.

Too Little Sleep vs. Too Much Sleep

Scientists still have a lot to learn about the specifics of the relationship between sleep and inflammation. But there’s already a strong body of research showing that lack of sleep raises levels of inflammation in the body. Laboratory studies have tested acute, prolonged sleep deprivation—conditions under which sleep is restricted for 24 hours or more—and found this severe degree of sleep loss increases inflammation activity in the body. Scientists have also studied partial sleep deprivation, the kind of chronic, insufficient sleep that so many people experience in their daily lives. While the study results are mixed, many studies show this form of everyday sleep loss also elevates inflammation.

It might surprise you to learn that sleeping too much can also trigger unhealthful inflammation. A 2016 study reviewed more than 70 scientific investigations into the relationship between inflammation and sleep. It found that in addition to short sleep’s negative effects on the immune system’s inflammatory response, sleeping excessively also raised levels of key inflammatory markers, including C-reactive protein, which is associated with heart disease, high blood pressure and type 2 diabetes.

Getting the right amount of sleep for you — for most adults, that’s at least 7 hours a night — on a consistent basis is one way to help avoid low-grade, systemic inflammation that’s associated with aging and chronic disease.

Just One Night of Poor Sleep Can Spike Inflammation

The long-term effects of poor sleep on health are a major public health concern. The influence sleep can have on inflammation is a significant factor in managing health and guarding against disease over the course of our lives. But it doesn’t take years, or months, for sleep to have negative effects on inflammation levels. According to research, it takes as little as a single night. Research has shown that one night of insufficient sleep is enough to activate pro-inflammatory processes in the body. A 2008 study found that one single night of partial sleep resulted in significantly higher levels of NF-kB, a protein complex that acts as a powerful signal to stimulate inflammation throughout the body. One noteworthy aspect of this study: the researchers found the higher inflammatory response occurred in female subjects, but not in male subjects. The differences in the ways women and men respond to sleep loss are important, and under-studied. Sleep’s effects over inflammation may be one area where women and men experience different degrees of consequence—and that could have implications for their vulnerabilities to chronic disease. This is an area of study that needs more attention.

It’s easy to write off a single night of poor sleep as no big deal. But every night of sleep counts. Along with your ability to function at your best mentally, and feel your best physically, a commitment to getting a full night of restful sleep makes a difference at a cellular level, in your body’s ability to keep inflammation in check.

Stress in the Sleep-Inflammation Relationship

You’ve heard me talk before about the deep connections between sleep and stress. Stress is a common obstacle to sleep. Worried, on high alert, agitated and anxious—these emotional and physical states of stress make it difficult to fall asleep and to sleep soundly throughout a full night. In turn, not getting enough sleep makes us more vulnerable to the physical and emotional effects of stress. We’re more likely to sink deeper into a stressful state when we’re tired and short on rest. Many people fall into a difficult cycle: ending the day stressed out, having a hard time sleeping, feeling exhausted and even more stressed the next day—which leads to more problems sleeping.

This chronic sleep-stress cycle does more than make us tired and irritable. Stress is also a trigger for inflammation. At a biological level, our bodies respond to mental and emotional stress as they would to a harmful pathogen, or to a direct physical threat: with a “fight or flight” response that alters immune system functioning and kicks inflammation into higher gear. Over time, chronic stress creates systemic, low-grade inflammation that wears at the health of our cells and makes us more vulnerable to disease.

We’ve all heard the adage that stress is bad for our health. Science is now identifying just what that means, and how stress contributes to disease by stimulating inflammation. A 2017 study identified the critical connections between chronic stress, increased inflammation, and the development of a range of diseases including cancer, heart disease, diabetes, and depression. Researchers in this study illustrate a relationship where stress-induced inflammation is the “common soil” from this spectrum of serious, chronic diseases can grow.

Sleep has a powerful, dual role to play in this complex interaction with stress and inflammation. Sleeping well can work directly to keep inflammation in check by avoiding the pro-inflammatory activity that occurs in the presence of poor, dysregulated sleep. And sleep offers us significant protection against stress, itself a major contributor to chronic inflammation—a now known pathway to disease.

Gut Health Matters, too

One of the most exciting areas of sleep and health research involves the human microbiome. Our microbiome is the vast, dynamic, ever-shifting collection of bacteria and other micro-organisms that live within our bodies. The largest collection of this microbial life resides in our intestines—hence, the focus on “gut health.” This intestinal body of microbiota is often referred to as the “second brain,” because of its profound influence over how we think, feel, and function.

We’re learning more all the time about the importance of gut health to sleep and overall health. An unhealthy gut contributes to chronic inflammation. How does a gut become unhealthy? Poor diet, stress, medication and illness are all contributors. So, too are disrupted circadian rhythms and poor sleep. Poor and insufficient sleep appear to change the composition of our natural microbiota, decreasing beneficial bacteria and increasing bacteria associated with disease. The emerging science points to a powerful two-way street between sleep and gut health. Sleeping well is one way to help maintain a healthy gut. And maintaining gut health—by managing stress, exercising, eating a healthy diet that’s rich in prebiotic (fiber-rich) foods—can help you sleep better. Both those pillars—healthy sleep and a balanced, thriving gut—can work to limit harmful inflammation, and may help deliver long-term protection against disease.

Chronic and systemic inflammation doesn’t always come with symptoms. But that doesn’t mean it isn’t a pervasive risk to our health. Sleep well can be a potent tool in helping guard against this often silent, and damaging, form of inflammation.

About The Author

Dr. Michael Breus

Clinical Psychologist, Sleep Medicine Expert

Michael Breus, Ph.D is a Diplomate of the American Board of Sleep Medicine and a Fellow of The American Academy of Sleep Medicine and one of only 168 psychologists to pass the Sleep Medical Specialty Board without going to medical school. He holds a BA in Psychology from Skidmore College, and PhD in Clinical Psychology from The University of Georgia. Dr. Breus has been in private practice as a sleep doctor for nearly 25 years. Dr. Breus is a sought after lecturer and his knowledge is shared daily in major national media worldwide including Today, Dr. Oz, Oprah, and for fourteen years as the sleep expert on WebMD. Dr. Breus is also the bestselling author of The Power of When, The Sleep Doctor’s Diet Plan, Good Night!, and Energize!

  • POSITION: Combination Sleeper
  • TEMPERATURE: Hot Sleeper

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