Strengthen Your Immune System

Scientists don’t have all the answers, but exercise, proper diet, and stress management can make you more resilient at any age

One aspect of the COVID-19 pandemic that has kept us guessing since the early days is why some people who get the virus don’t suffer much and others become desperately ill. All the more, while the elderly have been particularly hard hit, some—even centenarians— survive, whereas countless younger people, whose immune systems are supposed to be more robust, have succumbed to it. So what factors give some people a stronger immune system than others, regardless of age? What does it mean if, for example, your partner or child gets sick and you don’t, or vice versa?

We know that our immune systems slowly decline as we age. Doctors call it immunosenescence. It’s slow and insidious. Think of a photo of yourself from ten years ago versus one taken this afternoon. “You see changes in your face, skin, and hair color,” says Insoo Kang, MD, director of allergy and immunology at the Yale School of Medicine. “It takes time. Same process with your immune system.”

The difference in rate of decline between individuals is one of science’s big mysteries. The immune system is complex, but most of us understand the basics: Our bodies detect an intruder—a virus, bacterium, parasite, or foreign object—and produce white blood cells to combat the problem.

How many of these cells you produce when you’re, say, 73 versus when you were 45 is the million-dollar question. And it’s at the heart of the COVID-19 pandemic.

Fortunately, we won’t always be in a pandemic. But we can use this one to gain an understanding of how the immune system changes with age and how we might slow the decline and stay stronger in the future.

Immunity and Aging

No one knows why our bodies don’t produce as many immune cells as we get older, says Atul Butte, MD, distinguished professor of epidemiology, biostatistics, and pediatrics at the University of California, San Francisco. Dr. Butte worked with a research team on a review of 242 studies that revealed some insights, especially regarding T cells, which are white blood cells that attack viruses. We possess two broad categories of T cells: “memory” cells that have encountered a certain pathogen and “remember” how to fight it and “naive” cells, which have yet to fight anything. “We’ve seen especially that the number of naive T cells seems to be lower as we age,” Dr. Butte says.

And those are exactly the cells “needed to recognize newly emerging microorganisms like the COVID-19 virus,” says Dr. Kang. This means that when that virus—something our immune systems haven’t seen before— shows up, most of us don’t have memory T cells to mobilize, so the naive cells have to take on the fight. Since older folks have fewer naive cells to fight with, as a group they are more vulnerable.

But Dr. Butte observed in his study review that some healthy older people had little or no decline in T cells. Some had as many as younger people, and women generally seemed to have higher amounts as they aged.

The reasons these key cells decline over time could be manifold. “We know genetics plays a part,” Dr. Butte says. “But it’s debatable how big a part compared with environment and lifestyle.”

Chronic low-grade inflammation that develops with advanced age can also affect the immune system. Lifestyle factors—poor sleep, ongoing stress, and weight gain—are common causes, as are systemic issues such as autoimmune diseases and decreased liver or kidney function. This inflammation causes the immune system

WHAT FACTORS GIVE SOME PEOPLE A STRONGER IMMUNE SYSTEM?

to operate abnormally by constantly firing, which accelerates the aging process on a cellular level and can lead to heart disease, type 2 diabetes, Alzheimer’s disease, and more.

“Most systems in our body are tightly regulated,” says Sean Xiao Leng, MD, a professor at the Geriatric School of Medicine at Johns Hopkins University. “The immune system is no exception, which is why this dysregulation is so dangerous.” What’s more, chronic inflammation is silent and produces no symptoms. Your immune system may be compromised and you don’t even know it.

Taking Charge

When we talk about vulnerability in older adults, there are two important parts: incidence (whether you get an infection of any kind) and severity. If you do become infected, “having a stronger immune function may determine how badly you’ll be infected,” says Dr. Leng.

While you can’t do anything about your genetic makeup and you may not be able to completely stop the decline in your immunity as you age, slowing it down can mean a higher immune reserve when you need it most. Fortunately, many factors that positively affect your immune system are within your control, including these:

Movement Regular workouts boost immune function and lower inflammation. A 2019 study in

Nature noted that Reviews Immunology skeletal muscle is a “major immune regulatory organ” that generates antiinflammatory and immunoprotective proteins called myokines. A 2018 study found that higher-intensity workouts may blunt immune system decline in older adults. “Exercise strengthens the body and may be the most important lifestyle intervention you can add,” Dr. Kang says.

Self-knowledge Dr. Butte suggests that people gain a better understanding of where their health is right now. For example, those with asthma may want to start measuring their peak airflow to know what their normal lung function is. “The more we can use digital devices and tools, the more we’ll understand,” he says. “If something changes, you’re not just going to the doctor and saying, ‘I’m having trouble breathing.’ You can say, ‘My airflow has dropped 8 percent.’” Staying on top of chronic conditions will allow you to spot declines quickly so you and your doctor can decide on a better course of therapy.

Nutrition Eating right and avoiding obesity, whose inflammatory effect is deadly, are common sense. But research also reveals specific effects of diet on immune function in older adults. A study reviewed in the journal in 2018 showed that basic

Nutrients nutrients such as vitamins A, C, D, and E and the B vitamins, along with folic acid, iron, selenium, and zinc, are essential for “immunocompetence,” with deficiencies causing lower T cell

production and an inability to resolve inflammation. Strive for balance. “Eat not just vegetables but also good proteins and fiber,” Dr. Kang says. The latter is important because it feeds the good bacteria in your gut and can help lower inflammation. “We have a lot of immune cells in the gut that help regulate health. Dietary fiber may have more than the single effect of making the bowel move.”

Calm Research has shown that unregulated stress can accelerate immunosenescence since a chronic immune response to whatever’s stressing you can result in inflammation. Self-care in this area is critical, from anti-stress activities (meditation, mindfulness, exercise) to asking for help in unresolved stressful situations (work, money, caregiving).

Vaccines Vaccines are designed to provoke the production of antigens, but our aging immune reserve doesn’t respond as robustly as it did in our earlier years. That shouldn’t make you lazy about vaccines. “It’s true they become less effective as people get older,” Dr. Kang says. “But even if you do get infected, the disease will be less severe. People should get whatever vaccines their doctors recommend based on age and underlying medical conditions.”

Medications Certain prescription medications may inhibit your immune system. For example, oral and inhaled corticosteroids (common treatments for arthritis, allergies, asthma, and inflammatory bowel disease) may raise your risk of fungal infections. The same is true for tumor

your situation with a doctor who is familiar with your medical history.

Asthma, COPD, and other respiratory diseases Viruses love to attack the lungs, so people who have existing lung conditions are at risk of more severe symptoms when they do get sick. Chronic obstructive pulmonary disease (COPD) patients are particularly vulnerable to lung infections, which can further damage the already compromised air sacs.

Autoimmune diseases Not only can an infection trigger a flare-up of autoimmune diseases such as rheumatoid arthritis, multiple sclerosis, or psoriasis, the treatment of those conditions often involves immunosuppressive drugs that can raise your infection risk. Also, autoimmune conditions can cause interstitial lung disease, a dangerous condition that can cause scarring of the lungs.

Heart disease Based on early data, as many as 40 percent of COVID-19 patients who required hospitalization had existing cardiovascular disease, the American College of Cardiology reports.