Terms to Know
- Immunosenescence: Natural tendency toward diminished immunity as we age
- Inflammaging: Natural tendency toward more inflammation as we age
- T cells: White blood cells that attack viruses
- B cells: White blood cells that make antibodies to fight infection
- Memory cells: T cells that “remember” past viruses and give us immunity to them
- Naive cells: T cells that “teach” themselves to fight new viruses, such as COVID-19
- Cytokines: Small protein molecules released by a variety of cells in the body that help regulate immune response and inflammation. When the immune system is dysregulated, the body can overproduce cytokines, causing inflammation and disease.
- Myokines: Immune-boosting, anti-inflammatory compounds released by muscle that bolster the immune system
Aging Effect No 1: Fewer Immune Cells
Our body simply doesn’t produce as many immune cells as we get older, says Atul Butte, M.D., distinguished professor of epidemiology, biostatistics and pediatrics at the University of California, San Francisco. “And no one really knows why.”
Butte worked with a research team on an extensive review of 242 immunity studies that revealed patterns in how our immune systems change as we get older. Certain key immune cells — B cells and T cells, which are the virus fighters — become fewer in number with age. For example, we possess two different types of T cells: “memory” cells that have encountered a certain pathogen and “remember” how to fight it, and “naive” cells that have yet to fight anything. “We’ve seen especially that the number of naive T cells seem to be lower as we age,” Butte says.
So let’s say COVID-19 shows up. Nothing we’ve seen before as humans matches this one, so we have no memory T cells to mobilize. The naive cells have to take on the fight, and older folks have fewer of those to fight with. That makes us more vulnerable.
Or rather, that makes most of us more vulnerable. The mystery of immunity decline is complicated by the fact that not everyone’s immune system declines in the same way. For example, another factor Butte observed in his study review: Some healthy older people had little or no decline in T cells. Some had as many as younger people, and women seemed to have higher amounts in general as they aged.
Part of the reason B and T cells are so enigmatic is that no one really knows just what a healthy amount of B and T cells is. Says Butte: “If you want to have a test for your hemoglobin, they know what a normal range is. If you want your iron levels tested, they know what the normal range is. We have no idea what the normal level is for these cells. We don’t even measure them in a regular blood test.”
The reasons these key cells decline over time could be manifold: Our bone marrow produces white blood cells. Is that where the problem lies? Is it genetic? Lifestyle? An apple a day? All of the above? All immunologists can do is keep looking. “We know genetics plays a part,” Butte says. “But it’s debatable how big of a part compared with environment and lifestyle.”
Aging Effect No. 2: Rising Inflammation
Aging Effect No. 2: Rising inflammation
The term immunosenescence has a partner term that’s relatively new: “inflammaging.” It refers to chronic low-grade inflammation that develops with advanced age.
Inflammation — when the immune system causes a part of your body to become reddened, swollen, hot and sometimes painful — is how the body fights disease, fixes injuries and rids you of inappropriate germs or invaders. It’s meant to be short term. But chronic inflammaging tends to occur with age for a variety of reasons: Weight gain, poor diet, lousy sleep and chronic stress are among the big lifestyle causes. But other systemic issues can also contribute, such as persistent viral infections, decreased liver or kidney function, increased gut permeability (leaky gut) and autoimmune diseases.
All of this degrades the immune system; when our bodies are in a state of chronic, low-grade inflammation, our immune system is constantly firing and operating abnormally. That accelerates the aging process on a cellular level. It 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, M.D., professor of medicine, molecular microbiology and immunology at the Johns Hopkins University School of Medicine and Bloomberg School of Public Health. “The immune system is no exception, which is why this dysregulation is so dangerous.”
If it gets bad enough (a twofold to fourfold increase in blood levels of inflammatory cytokines, according to one 2019 study), a person can officially become a “chronic low-level inflammatory phenotype.” You don’t want to be that person.
The insidious nature of chronic inflammation is its relationship to so many organs and processes in the body. For example, unregulated stress (inflammatory) can motivate you to stress-eat highly processed sugary/fatty/salty foods (inflammatory), and they can also pack a calorie punch for weight gain (inflammatory), promote a poor bacterial balance in your gut microbiome (inflammatory), and over time push you into metabolic syndrome or type 2 diabetes (inflammatory).
What’s more, chronic inflammation is silent and produces no symptoms. Your immune system may be compromised and you don’t even know it.
How to save your immune system
You can’t do anything about your genetic makeup, but, luckily, many factors that positively affect your immune system are within your control. Take them seriously, Leng urges. While you may not be able to stop immunosenescence, any slowdown you can produce means a higher immune reserve at any given time. That’s critical when it comes to infections.
“If you talk about vulnerability in older adults, it’s definitely two important parts,” he says. “One is incidence — whether you get the infection or not. But the other part is severity. Even if you don’t have the incidence outcome you want, having a stronger immune function may determine how badly you’ll be infected.” In other words, every bit of the following helps.
Regular workouts boost immune function and lower inflammation. A 2019 study in Nature Reviews: Immunology noted that skeletal muscle is a “major immune regulatory organ” that generates anti-inflammatory and immunoprotective proteins called myokines. A 2018 study found that higher-intensity workouts may blunt immunosenescence in older adults. “Exercise strengthens the body and may be the most important lifestyle intervention you can add,” Kang says.
Obesity is deadly when it comes to inflammation. Belly fat is metabolically active tissue; it releases inflammatory cytokines into your body, which then trigger more weight gain — and more inflammation. Kang states it simply: “Getting to a healthy weight could be a major factor in decreasing inflammation levels.”
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 whatever chronic conditions you have will allow you to spot declines quickly, so you and your doctor can decide on a better course of therapy.