Why Your Immune System Declines as You Age — and 5 Things to Do About It

Every cold and flu season, and especially now during the novel coronavirus outbreak, we're reminded that older adults tend to be hit harder by viral infections and other illnesses. That's mostly because, as we age, our immune systems start to weaken.

This gradual decline in immunity, known as immunosenescence, is one reason why older adults are at increased risk of health issues — from chronic diseases (such as heart disease and cancer) to dangerous complications (such as pneumonia) from illnesses like COVID-19. Immunosenescence even makes protective vaccinations, like the flu shot, less effective in older people, according to Harvard Health Publishing.

And while scientists agree that part of this process is natural and inevitable, studies suggest that there is also a lot that older adults can do to preserve and strengthen their immune systems.

Here's what's happening with the body's natural defenses over time, and how we can protect ourselves well into our golden years.

Some of the most obvious signs of aging are physical: As we get older, we develop wrinkles as our skin loses its elasticity and we go gray as our hair loses its pigment. Some signs are mental: Memory loss becomes more common and some people develop degenerative brain diseases like dementia.

At the same time, something similar but less obvious is happening to the body's aging immune system.

"It's the same with every organ in the body," says Nir Barzilai, MD, director of the Institute for Aging Research at the Albert Einstein College of Medicine. "Things begin to break down, and the body can't repair it as quickly and completely as it once could."

To a certain extent, that's just a normal part of aging, says Jessica Lee, MD, assistant professor of geriatrics and palliative medicine at the University of Texas Health McGovern Medical School. "Unfortunately, the body just doesn't produce immune cells the way it used to at a younger age," she says.

B and T cells — two types of white blood cells that make antibodies to fight off outside pathogens — are produced less frequently in older adults, Dr. Lee says. "They're also potentially of a lower quality," she adds, "which makes it difficult for the body to mount an immune response when it's attacked by something like a virus or bacteria."

On top of that, levels of inflammation in the body tend to rise as we get older, as well — a phenomenon known as inflammaging, according to a July 2018 review in ​Nature Reviews Endocrinology.​

"When we get an infection and we get a fever, that's inflammation," Dr. Barzilai says. "But if our inflammatory response is too high in these situations, it can be very dangerous."

Yes, a decrease in immunity over the years is normal. "But I don't want to sound like it's all doom and gloom, and it's just too bad if you're old because there are ways you can boost your immunity to help offset that natural decline that comes with age," Dr. Lee says.

"Aging is a modifiable condition. It's flexible — and if you can lower your biological age, you're going to be better protected against viruses and other threats."

Dr. Barzilai agrees, adding that there are really two types of aging: chronological, which keeps track of a person's actual age, and biological, which takes into account how healthy people are compared with their peers.

"Aging is a modifiable condition," says Dr. Barzilai. "It's flexible — and if you can lower your biological age, you're going to be better protected against viruses and other threats."

Here are a few ways to do just that. Not only will these strategies help you feel younger, but they'll do the same for your immune system as well.

​1. Get Plenty of Vitamins and Minerals From Whole Foods​

Eating a healthy diet rich in antioxidants, fiber and other important nutrients is one of the best ways to strengthen your immunity at any age, says Dr. Lee — but it's especially important for older adults who are starting to lose those natural defenses.

"I recommend eating as many fruits and vegetables and whole foods as possible, and trying to avoid processed foods that are high in sugar and fat," she says.

One nutrient older adults shouldn't skimp on is zinc. Zinc deficiency is common in older adults, according to a 2012 review in ​Aging and Disease​, and has been linked to impaired immune function and an increased risk of infection.

Shellfish, eggs, soy products, legumes and whole grains are all good sources of zinc. You can also get zinc from dairy sources such as milk, cheese and low-fat yogurt.

Or, you might consider taking a daily zinc supplement — but only do this under a doctor's supervision, since too much zinc could also harm the immune system, per the ​Aging and Disease​ study.

Older adults might benefit from taking a vitamin D supplement, as well. The body depends on vitamin D to regulate the immune system, according to a December 2018 review in the ​Journal of Aging and Gerontology​​,​ and many older adults don't get enough from sun exposure and diet alone.

Adults up to age 70 should get 600 IU of vitamin D daily and adults 70 and older get 800 IU a day, per the National Institutes of Health.

​2. Exercise Regularly​

Regular physical activity is important, too.

A September 2013 literature review in the journal ​Maturitas​ notes that exercise has been shown to increase both the number and function of immune-system cells in older people, as well as reduce inflammation.

Only certain types of exercise have been studied in clinical trials. For example, a study in the March 2018 journal ​Aging Cell​ observed that older adults who cycled regularly had levels of T cells in their blood similar to young adults who weren't involved in regular exercise.

And a 2012 study in the ​Journal of Sports Medicine & Doping Studies​ observed that a six-month tai chi program significantly increased immune-system activity in middle-aged and older women.

"Find the exercise that you like the most and feel like you're going to stick with for the long haul. I don't care what it is, as long as you're moving."

Cycling and tai chi are both smart choices for older adults to consider because they're low-impact and easy on joints, which helps keep injuries away. But they're also just two examples of physical activity that can help you stay safe from dangerous illnesses.

"The best thing for older people [for supporting immunity] is exercise — any type of exercise — so it's important to find a way to do it on a regular basis" Dr. Barzilai says. Waking outdoors can be one way, he says. Or, if people are stuck inside due to weather or other obstacles (like social distancing protocol), a treadmill or exercise bike might be another option.

Dr. Lee says the most important thing to keep in mind when making an exercise plan is whether you'll actually do it. "Find the exercise that you like the most and feel like you're going to stick with for the long haul," she says. "I don't care what it is, as long as you're moving."

​3. Maintain (or Get to) a Healthy Weight​

A healthy diet and exercise plan may directly support your immunity for the reasons listed above — but they may also have an indirect benefit, which is helping people lose weight or maintain a healthy weight.

Overweight people and people with obesity tend to have higher levels of inflammation in their bodies than their healthy-weight peers, which can make it harder to fight off infection and other threats.

In fact, a 5 percent loss of total body weight in overweight people and people with obesity was associated with lower levels of inflammatory proteins in the blood of older adults (average age 65), according to a February 2015 study in the journal ​Osteoarthritis and Cartilage.​

​4. Quit Smoking​

Giving up cigarettes and other forms of tobacco will, first and foremost, reduce your risk of cancer and respiratory disease. But it can also have far-reaching effects on the immune system.

That's because smoking contributes to inflammation not just in the airways, but throughout the entire body, Dr. Lee says.

It's also been linked to frailty — a precursor to disability that includes an increased vulnerability to health problems — in older adults. Current smokers aged 60 and over were 60 percent more likely to develop frailty than non-smokers in the same age group, in a January 2018 study published in ​Age and Aging.​

The good news? Former smokers had no increased risk of developing frailty compared to those who never smoked, regardless of whether they'd quit in the last 10 years or prior to that. In other words, it's never too late to kick the habit and reap the health benefits.

​5. Manage Stress and Emotional Health​

Finally, it's not just your physical health that affects your immune system; it's also about how you deal with stress and your emotions.

Feelings like chronic sadness and loneliness have been linked to lower immune responses, according to the National Institute of Aging. And about a third of Americans aged 45 and older reported being lonely in a 2018 AARP survey.

Adults who are no longer working, are living alone after the death of a spouse or are physically unable to get out and about are at increased risk for loneliness and social isolation. But maintaining social connections with friends and family members — or by taking part in organizations like book clubs, choir and religious groups — can help, according to the American Psychological Association.

Mindful practices can also help people of all ages manage feelings of anxiety and depression, Dr. Lee says. An October 2012 study in ​Brain, Behavior, and Immunity​ found that an 8-week meditation and yoga practice was associated with reduced loneliness — and reduced markers of chronic inflammation — in older adults.

"Anything that helps you center yourself certainly has the potential to help your immune system," Dr. Lee says.

"That's especially important during stressful and uncertain times, and especially important for older adults who are more at risk."