How Lack of Sleep Makes You Sick

Ask the average American what it takes to avoid illness, and most will tell you that you should steer clear of large crowds, wear a mask, use hand sanitizer, and perhaps even get a shot. That’s the message that has been strewn across television screens and social media. It’s also the advice coming out of the mouths of some of our most trusted health care providers. They certainly don’t say anything about sleep and the immune system.

What if we told you that we know another way to stay healthy? A better way! It costs nothing, has no side effects, requires minimal effort, and feels incredibly good. What could this miracle drug be, you ask? Sleep! Sleep is by far one of the best ways to keep healthy, and a lack of quality shut-eye wreaks havoc on your immune system. 

Sleep by the numbers

It wasn’t that long ago that Americans clocked, on average, eight to nine hours of sleep each night. Today, over a third of adults report sleeping less than seven hours. Sleep duration and quality have declined significantly over the past few decades, as evidenced by the following: 

Why are we sleeping less? 

The prevalence of sleep problems is multifactorial, with technology being the biggest culprit. Smartphones, iPads, and laptops abound, contributing to an exhausted society.

Let’s be honest: How many times have you picked up your phone to check the time or a text message, only to realize you are still scrolling an hour later? These addictive devices destroy sleep. For example, a recent study found that individuals who spent a lot of time online had impaired sleep quality and duration. 

In addition to the addictive quality of electronic devices, the blue light emitted from these devices impacts our circadian rhythm, making it harder to fall asleep and stay asleep. 

Other factors that impact sleep in today’s world include increased economic stress and the demands of modern life. Longer work hours, extended commutes, and two-income households contribute to a sleepless society. With the ever-increasing pressure to function in our 24/7 world, sleep is often placed on the back burner, much to the detriment of our health. 

Different types of sleep disturbances

From sleep apnea to narcolepsy, medical experts have identified over 100 different sleep disorders. Sleep problems typically manifest in one of the following ways: 

  • Difficulty falling asleep 
  • Difficulty remaining asleep (disrupted sleep) 
  • Problems with sleep quality
  • Difficulty staying awake
  • Nighttime behaviors that impact sleep quality such as snoring, sleep apnea, sleepwalking, or restless legs syndrome. 

Circadian rhythm and sleep  

How does your body know when to wake up in the morning? Each and every one of us has an internal clock that tells us when to sleep, wake up, and eat. Using clues in our environment, such as sunlight and temperature, our internal clock signals various functions in our body over 24 hours. This process is better known as circadian rhythm. The circadian rhythm influences the following:  

  • Sleep-wake cycle
  • Hormones and enzymes
  • Appetite and digestion
  • Body temperature
  • Immunity  
  • Overall health of the body

Just as the heart has a natural pacemaker called the SA node, the circadian system also has a pacemaker. Located within the brain’s hypothalamus, the suprachiasmatic nucleus (SCN) is in charge of regulating the body’s internal clock. This master clock communicates with peripheral clocks that live in our organs and tissues, as well as in specific cells of our immune system. 

The circadian rhythm is best balanced by going to sleep and waking at the same time each day, preferably with the sun’s rising and setting. This is because morning sunlight tells the body to produce more of the feel-good hormone, serotonin, while suppressing the sleep hormone, melatonin. 

Disruptions to the circadian rhythm can result in mood disorders, obesity, fatigue, viruses, and other chronic health problems, including immune system disorders.

Immunity 101

To understand how sleep impacts immunity, we must understand how the immune system works. The immune system is our natural defense system. 

Like soldiers guarding their homeland, the immune system is responsible for destroying foreign substances that it believes to be a threat. Likewise, it springs into action when the immune system detects unwanted bacteria, viruses, or parasites. 

The immune system has two armies of cells. Innate immune cells are those we are born with and our first line of defense. However, as we grow, we also acquire immunity when exposed to different foreign invaders. These adaptive immune cells have memory and care for invaders that our innate cells cannot fight. 

When the immune system soldiers detect an invader, white blood cells are called upon. Also called leukocytes, these white blood cells (created in the bone marrow) are the main drivers of the immune response. 

The three main types of leukocytes are basophils, lymphocytes, and phagocytes. In addition, there are two different types of lymphocytes involved in the immune process: T-cells and B-cells. 

During an immune response, T-cells multiply and release chemicals called cytokines. These cytokines then trigger the stimulation of B-cells. Once prompted, B-cells produce infection-fighting antibodies which attach themselves to the infected cells. T-cells destroy the invaders, and phagocytes eat them up. Once the battle is over, some of the T and B cells remember the invader, creating immunological memory.

How circadian rhythm influences immunity

Scientists have recently discovered that immune cells respond differently depending on the time of day. As a result, whether or not we acquire an infection, how severe the condition becomes, and how well it resolves are all impacted by circadian rhythm. 

The mechanism by which the immune system changes and adapts in a 24-hour period is still not fully known. However, one possible answer is related to the stickiness of T-cells. 

Sticky molecules called integrins help T-cells attach to invaders. Stress hormones such as adrenaline make T-cells less sticky. These stress hormones are decreased during sleep, allowing for T-cells to do their job more effectively. 

In another recent study, researchers found that large, bacteria-killing cells called macrophages responded to invaders differently depending on the time of day. 

Sleep and the immune system

Believe it or not, when we are seemingly doing nothing, our bodies are the most productive. Many of our bodily functions, such as breathing and heart rate, slow down during sleep. This frees up the immune system’s energy to repair cells and remove waste.  

Sleep has been shown to benefit the immune system by: 

Sleep does more than protect the immune system. It also protects the heart. In one Harvard study, researchers found that high-quality sleep protected against atherosclerosis. Multiple other studies have confirmed that poor sleep is associated with an increased risk of cardiovascular disease. 

A tired immune system can’t protect 

Research shows that people who don’t get quality sleep are more apt to get sick. For example, studies have found that individuals who sleep less than seven hours a night are three times more likely to catch the common cold. 

Another study found that women who slept less than five hours a night were 70 percent more likely to get pneumonia than those who had a solid night of sleep. Scientists have also found that those with obstructive sleep apnea are at a higher risk of contracting a Covid-19 infection. 

What’s more, sleep can also impact how fast one recovers from illness. Studies have found that sleep is a powerful tool when used to heal.

Is there such a thing as too much sleep?

By now, it’s clear that quality sleep is essential for strong immunity. However, this is not a free ticket to sleep your life away. Oddly enough, too much sleep can also weaken the immune system. 

Oversleeping, defined as sleeping more than nine hours a night for adults, is associated with an increased risk of death from cardiovascular and other diseases. Research suggests that longer sleep: 

Sleep needs are specific to each individual, but seven to nine hours appears to be the sweet spot for optimal health and immune function. 

Next steps

Doctors are quick to prescribe sleeping pills, but the real answer might be prescribing sleep itself! Nightly sleep allows our bodies to restock the weaponry within our immune system. During sleep, the body increases its production of immune cells, resulting in a stronger, more robust body. Visit our Sleep lifestyle page for more information on the importance of sleep and proven strategies to help you get a better night’s rest.

Bottom line: Sleep is the best health insurance policy you could ever purchase. And it’s free!

Eat Well · Live Well · Think Well 


Medical Review 2022: Dr. Lauren Lattanza NMD

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