Here’s Why a Lack of Sleep Can Mess With Your Immune System

You already know how important sleep is and yet it can feel so elusive when you need it the most—which is probably right now, when the holidays are more overwhelming than exciting, work deadlines feel extra tight, and your family’s group chat is going off the rails. But consider this if you’re exhausted: Getting quality sleep (and enough of it) plays a role in keeping your immune health in good shape.

“The immune system, when working correctly, is complex and elegant,” Kara Wada, MD, an allergist and immunologist at The Ohio State University Wexner Medical Center, tells SELF. It’s a smart network of cells, proteins, and organs that can “rapidly recognize what is not welcome” in your body, she explains, including germs that can make you sick. When your immune system detects viruses or bacteria, it typically fires off a swift response to shut down the threat they pose to your well-being.¹

How does sleep fit into this process? Even if you’re a generally “healthy” person, here’s what you should know if you’re struggling to get good rest in the thick of cold and flu season.

How sleep supports your immune system

“Sleep is the time when your brain and body are in rest, repair, and recovery mode,” Dr. Wada says. “The quality and quantity of your sleep help keep your body in optimal form and function.”²

While you snooze, your body produces new protective cells as well as proteins called cytokines that help regulate your sleep and immune function, Dr. Wada says.³ Your immune cells then make their way throughout your body, from your blood to your lymph nodes to your organs. “During this migration, the immune cells communicate with one another, playing a game of matchmaker,” Dr. Wada explains. “It is this process that is critical in fighting off infections.”

And all of this is inherently tiring, Otto Yang, MD, an immunologist and the associate chief of infectious diseases at UCLA Health, says. “The cells that are part of the immune system consume a lot of energy to do their job,” he tells SELF.

That’s one reason why fatigue from, say, the flu can hit you so hard and fast. When you’re sick, “your body will actually encourage you to get more rest by increasing signals that promote sleep,” Dr. Wada says.⁴And if you’re also wiped out because you haven’t been sleeping well in general, your body may have a hard time dishing out its resources (a.k.a. energy) to your immune response—especially when a strong one is needed to help you recover from a cold, the flu, or another bug.³

So can a lack of sleep increase your chances of getting sick?

Not getting enough sleep does not directly make you sick, but it doesn’t help your immune system’s chances of preventing an infection, according to W. Christopher Winter, MD, a neurologist and sleep medicine physician with Charlottesville Neurology and Sleep Medicine, tells SELF. For example, research has found that people who get fewer than six hours of sleep a night are significantly more likely to catch a cold compared to folks who clock in more than seven hours.⁵

Consistently not getting enough sleep can cause physical and mental stress—and when your body’s in this state, it pumps out hormones like cortisol, Dr. Wada says. If this happens daily—say, you’re tossing and turning every night and feeling like garbage because of it—it can become a vicious cycle. When cortisol levels get too high and stay that way for too long, inflammation in the body increases.⁶ Short-lived inflammation is a natural part of your body’s immune response. But chronic inflammation, which typically lasts several months to years, can heighten your risk of all sorts of health issues, including cardiovascular and autoimmune diseases.⁷

Researchers have also discovered that a lack of sleep can potentially affect your body’s reaction to vaccines. For example, one meta-analysis of 504 people concluded that those who reported getting fewer than six hours of sleep a night during the days around a vaccination against a viral illness, like the flu or hepatitis, had a “robust decrease” in their antibody responses than those who reported getting more rest.⁸ (Meaning their bodies didn’t create a strong supply of proteins that could specifically recognize and fight the viruses the respective vaccines were targeting—the entire point of the shots.)

“The research has largely involved vaccines for influenza, hepatitis A, and hepatitis B, but there is an assumption that we can extrapolate this [finding] to other vaccines, like the COVID-19 vaccine,” Thomas Russo, MD, a professor and chief of infectious diseases at the University at Buffalo in New York, tells SELF. “You have a low-grade inflammatory response when you’re sleep-deprived and that may influence antibody response.”⁹

As one paper put it, “It seems that sleep supports—and sleep deprivation impedes—the formation of the immunological memory.”³

All that said, your immune system is influenced by many factors—including your genetics, diet, and physical activity levels, among others—so sleep is just one piece of the puzzle that’s not fully understood by researchers yet.

If you’re having trouble getting enough sleep, start with the basics.

Are you getting at least seven hours of sleep daily? Are you going to bed around the same time each night, and waking up around the same time each morning? Are you keeping your phone and laptop out of your bed? Is your room dark and cool enough for deep rest? These are all solid habits that can help you clean up your sleep hygiene. Don’t overlook the simple stuff, Dr. Winter stresses.

If you’re doing all of this and you consistently can’t sleep through the night, feel wiped out during the day, wake up with headaches in the morning, or have trouble focusing because you feel so groggy, don’t hesitate to talk to a primary care doctor, who may refer you to a sleep specialist. “It’s never too early to speak to a doctor about sleep quality issues if you think there is a problem,” Dr. Winter says. “Often this is the key to getting the intervention and studies necessary to diagnose and treat underlying sleep disorders.”

You should also see a doctor if you seem to be sick all the time—or your infections become severe quickly. If you’re taking medication that can suppress your body’s natural defenses, or you potentially have an underlying condition like an immunodeficiency disease or type 2 diabetes, that’s when doctors “see an increased susceptibility to infections,” Dr. Wada explains. In these cases, sleep might temporarily help you feel better if you’re really tired—but it’s not a solution. You’ll need to work with your doctor to figure out if certain tests and treatments are needed.

Bottom line: One night of terrible sleep isn’t going to wreck your health, but consistently poor rest can trigger a ripple effect. You wouldn’t keep driving a car with barely any gas in the tank. And even if you did, that neglect would probably do some damage eventually. Your body is no different—listen to it when it’s running on empty.

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