Here’s an interesting way to think about your health: Your age and the age of certain body parts and systems aren’t always the same. If you regularly jogged on pavement for 10 years, for example, your knees may be “older” than the rest of your body. If you have pristine oral hygiene, your teeth may be “younger” than the rest of your body. And if you constantly experience a moderate to high level of stress, your immune system might be “older” than your body, too.
According to new research published in the PNAS Journal and conducted by a team at the University of Southern California (USC), stress — in the form of traumatic events, discrimination, day-to-day stressors, and job strain — can accelerate the aging of your immune system. And an aging immune system increases a person’s risk of developing age-related diseases — like heart disease, cancer, arthritis, and osteoporosis — much sooner than they should.
The Reason for the Research
As the USC researchers say in the study, your age typically mirrors your immune system’s age. For instance, the immune system of a young adult usually has a healthy balance of white blood cells (also called immune cells), antibodies, cytokines, and other helper molecules. (Antibodies are specialized proteins that can bind to foreign toxins, bacteria, and viruses. Cytokines are messenger proteins that help the body mount an immune response.)
Middle-aged adults tend to have fewer “naïve” immune cells, or cells that have never been exposed to foreign invaders. They also tend to have higher levels of cytokines, which cause more inflammation. (The reason? Some immune cells become “zombie” cells — also called senescent cells — which are dysfunctional but never die. Instead, these zombies continue to produce cytokines, which promote inflammation.) Both of these realities are part of the normal aging process.
However, the health of an older adult’s immune system is far less predictable. As the USC researchers explain, some older adults have immune systems that seem far older than the rest of their bodies. They have low levels of immune cells and high levels of inflammation, which may contribute to chronic diseases.
Why might some older adults have immune systems that are “older” than they actually are? The researchers theorized these adults experience greater levels of stress.
The Link Between Stress and a Poor Immune System
To test their theory, the USC team collected data on 5,641 adults across the US, all over the age of 50. The participants answered a questionnaire which assessed their levels of social stress. Social stressors included life events, chronic stress, everyday discrimination, and lifelong discrimination.
Next, the researchers collected and analyzed participant blood samples. The blood samples revealed not only white blood cell count, but also the types of immune cells present and their quality.
The study authors found that people with higher stress scores had “older” immune systems. More specifically, stress was linked to low levels of certain young, helpful immune cells and high levels of potentially harmful, aging immune cells. (Remember: naïve immune cells are those that have never been exposed to a foreign invader.)
Why might stress accelerate the aging of the immune system? The researchers point to previous studies, which show that social stress directly affects the immune system. It may increase inflammation and decrease the body’s response to pathogens.
Of course, the research must be taken with a grain of salt. Participants who experienced more stress tended to have poor diets and exercise habits. So, the accelerated aging of their immune systems was likely caused in part by poor diet and a lack of exercise.
What This Means for You
It’s important to recognize just how much daily stress can impact your health. Take a look at the stressors in your life. Do you experience (or have you experienced) any of the following?
- A traumatic event, such as the loss of a loved one
- Job strain (such as constantly working late)
- A high-stress environment at home or work
The more stressors you experience, the more likely it may be that your immunity will suffer. So, start making active changes in your life to reduce stress. Jot down the biggest sources of stress in your life so you can see them all laid out. Then, pinpoint one or two items you can work on. Consider seeing a therapist to help you learn concrete methods for stress relief.
Reducing your stress levels will take time, patience, and work, but there is some good news: It is linked to stronger immune health.