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How Aging Affects Your Immune System

US News & World Report - Health logo US News & World Report - Health 3/4/2022 Lisa Esposito
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As you get older, your immune system ages with you. There's even a medical term for it – immunosenescence – the gradual decrease in immune function that comes with age. Similar to your walking or running speed, your body's ability to fight off infection inevitably slows.

COVID-19 has added another health hazard for older adults. Once infected with the virus, people in their 60s, 70s, 80s and above are at increasingly higher risk of experiencing severe COVID-19 illness and complications, hospitalization and death.

Although its difficult to precisely measure the impact of immune-system aging, "We know that it adds a massive risk," says Dr. Janko Nikolich-Žugich, a professor and chair of immunobiology at the University of Arizona College of Medicine–Tucson. "Those over 80 are 260-fold more likely to die from COVID-19 than those between 18 and 39."

The good news is the COVID-19 vaccine is highly effective at any age – making full vaccination critical for older adults. Research confirms its value:

  • A large study of COVID-19 vaccination coverage and mRNA vaccine (Pfizer and Moderna) effectiveness included more than 6.5 million U.S. veterans. One-half of these participants were ages 65 and older. For full (two-dose) vaccination, average effectiveness against infection was 97% for participants overall, and 94% – still very high – for veterans ages 65 and older. Among participants who were immunocompromised, vaccine effectiveness was 87%.
  • Full vaccination is effective for preventing hospitalization in older adults, according to findings in the August 13 issue of the Morbidity and Mortality Weekly Report. The 13-state analysis showed 96% effectiveness for Pfizer and Moderna vaccines, and 84% effectiveness for the Johnson & Johnson vaccine in adults ages 65 to 74. For adults ages 75 and older, effectiveness was similar: Moderna (96%), Pfizer (91%) and J&J (85%).

Older adults are doing better than expected, says Nikolich-Žugich, who is also co-director of the Arizona Center on Aging. "There is a strong response after two doses of mRNA vaccines," he says. "We still do not know enough about it's durability or breadth – but so far, so good. Still, boosters are fully warranted for this population."

Besides getting COVID-19 and other recommended immunizations for your age group, you can do a lot to bolster your immune system and keep it as healthy as possible. Here are some reasons your immune system weakens and then proactive ways to support it.

Aging Effect Is Real

Your immune system keeps your body healthy by warding off foreign substances. Harmful invaders include bacteria, viruses, fungi and cancer cells. The immune system battles back through a complex network of blood cells and bodily organs. Lymph nodes are glands that harbor, then release, specialized white blood cells called lymphocytes. Lymph and blood vessels transport the infection-fighting lymphocytes throughout the body.

"Your age is the primary determinant of what's going to happen to your immune system," says Philippa Marrack, a researcher, professor and chair of immunology and genomic medicine at National Jewish Health in Denver.

The bottom line is that your immune system is just not as robust as it used to be, Marrack explains. As a consequence, it takes longer for your body to figure out when you have an infection. Once detected, it takes longer for the immune system to deal with it, as there are fewer white blood cells to respond, and your body starts losing the race between bacteria or viruses. You get sick more often. Infections are more severe and more of a threat than when you were younger, and you recover from them more slowly.

Vaccinations are key for protecting you from infection. However, some vaccines may not work as well as they used to. As the immune system changes, autoimmune diseases like rheumatoid arthritis are more likely to occur.

Experience does confer some benefit. "When you get older, your immune system is (still) pretty good at dealing with things you've already experienced," Marrack says. "But it's the new infections that you've never experienced before that are a real problem."

One example is the West Nile virus, Marrack says. West Nile virus disease, which affects older adults more severely, was far more lethal among those over 65 than younger adults when it first came through North America at the turn of the millennium.

Aging Immune System Plus Underlying Conditions

Immune-system aging increases COVID-19 risk "quite a bit," says Laura Haynes, a professor of immunology at the UConn Center on Aging at University of Connecticut School of Medicine. "But it's not only that older adults have a less robust immune system that makes them more susceptible to COVID," she says. "The vast majority of older adults have other comorbidities that also put them at risk for COVID." These underlying conditions put people at a greater risk of severe cases of COVID-19 with longer-lasting effects.

Being overweight, having diabetes, cardiovascular disease or preexisting lung conditions like chronic obstructive pulmonary disease become more common with age, Haynes notes. "So it's the perfect storm of not only changes in the immune system but also other changes that happen as you get older."


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Fortunately, COVID-19 vaccination still works really well in older adults, says Haynes, who explains why the Pfizer and Moderna vaccines are so effective. "They are a much different kind of technology than, say, our seasonal flu vaccines," she says. "They're more stimulatory to the immune system. So they work much better at stimulating a protective immune response in older adults."

Inflammation and Aging

Inflammation is part of the body's normal response to an injury, infection or toxin. With chronic inflammation, however, the body's ongoing response can damage healthy cells, tissue and organs.

The combination of inflammation plus aging, sometimes called "inflammaging," can have an unfortunate impact on health. "As you get older, for most people, the level of inflammation in your entire body goes up," Haynes says. "This is due to aging, to changes in your cells as you get older."

Inflammation is a factor in a variety of conditions from heart disease to dementia, Haynes says. "It's probably related to pretty much every disease of aging you can think of," she says. Increased inflammation could be at the root of age-related changes in physical function and reduced mobility, she adds. Inflammation can also impact how the immune system responds to a vaccine or an infection: "And that might make the response be not as protective as it would be in a younger person."

Within the cells, a phenomenon called "cellular senescence" is likely responsible for inflammation that comes with aging, Haynes says. "Normally, in a younger person, cells that are old and have accumulated defects because of their age are rapidly cleared from the body," she explains. "As you get older, it doesn't happen as efficiently – and so the cells hang around. They produce and generate more inflammation."

What You Can Do

Vaccinate, vaccinate, vaccinate. That's the first line of defense against common infections such as flu and pneumonia. Getting adult vaccinations according to recommendations is the best way to protect yourself from infectious diseases, Marrack emphasizes. One example is shingles – a painful, persistent infection that tends to prey on seniors.

"Shingles is caused by the chickenpox virus hiding away in our nerve cells ever since we got chickenpox when we were young," Marrack says. An intact immune system keeps the virus under control, sometimes for decades. However, she says, "As your immune system gets less effective, it can come popping out."

Vaccination against the varicella zoster virus, which causes shingles, is recommended for adults over 50, according to the Centers for Disease Control and Prevention. Shingrix, now the only shingles vaccine approved in the U.S., is highly effective at preventing shingles even in adults in their 80s and 90s.

Most people should receive yearly flu shots. Special formulations are targeted just for older adults. The Fluzone High-Dose Quadrivalent vaccine is one. "That has more of the flu antigens in it than the standard-dose vaccine, which younger adults get," Haynes explains. "It's more concentrated." FLUAD Quadrivalent, the standard yearly flu vaccine with an adjuvant added to boost protection, is also approved for people 65 and older.

Pneumococcal vaccines are advised for adults over 65 to prevent pneumonia and related conditions. In addition, you may need periodic booster shots for tetanus or other conditions, depending on your health history. Work with your health provider to stay on top of immunization schedules.

"You need to get your vaccines," Haynes says. "There's a lot of talk about natural immunity: letting your immune system fight off whatever infection you get. When you're older that's really a bad idea because your immune system is just not going to be up to the task on its own. So it's even more important for older folks to get the vaccines that their doctor recommends."

Beyond vaccination, masks, avoidance of crowded spaces, good sleep, diet and exercise help older adults protect themselves to mitigate their higher infection risk, Nikolich-Žugich says.

A healthy immune system is closely tied to your overall health. Avoiding obesity and keeping chronic conditions like diabetes under control reduces immune-system stress.

"The one big thing that keeps people younger – and it's been shown over and over again, in study after study – is exercise," Haynes says.

For instance, a March 2018 study highlighted the importance of exercise to counter aging. A team made up of 125 male and female cyclists, ages 55 to 79, was compared to a control group of older adults who did not exercise regularly. The cyclists not only had intact strength and muscle mass, but also possessed immune systems equal to those of much younger adults.

Good nutrition from eating a balanced diet also keeps your immune system strong. On the other hand, smoking is as bad for your immune system as it is for your lungs. Heavy alcohol use or binges can compromise immunity as well. Sleep disorders like sleep apnea can also lower immunity, so seek treatment if needed.

Hope for a Stronger Immune System

A growing body of research is looking at aging's effect on the immune system. "The main recent realization is that some immune (lymphoid) tissues, such as the lymph nodes, age earlier than we thought," Nikolich-Žugich says. "The aging of lymph nodes is critical to impaired maintenance an function of the immune cells. Lymph nodes are specific parking grounds where immune cells, particularly T and B lymphocytes, are maintained (and) where they react to infection. So, losing lymph node function is a pretty nasty proposition. There may be ways to reverse that loss, but this work is still in early stages."

In his own laboratory, Nikolich-Žugich's team is working to understand how to reinvigorate white blood cells that are critical to immune function. Another challenge is restoring coordination throughout the immune system so that infection-fighting cells can meet microbial challenges in time.

One potential treatment track is medications such as rapamycin and metformin, which have shown age-delaying and anti-inflammatory effects in animal studies. "This is a big area of research right now," Haynes says. "And there are a lot of companies trying to generate the perfect drug."

Certain experimental drugs are currently being evaluated for their ability to rid the body of worn-out cells that accumulate and cause harm. "What people are looking at now is the use of drugs called senolytics," Haynes says. "These will clear the senescent cells. In animal models, they've been shown to be really efficacious in restoring physical and metabolic function in old mice." The next step is happening: Clinical trials are now being conducted in people.

"The process of aging is inevitable, but it is also plastic – it can be modulated and delayed," Nikolich-Žugich says. "This is also true for immune aging, and there are many interventions to improve the function of the immune system that are candidates to be tested in humans."

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