Stress accelerates the aging of the immune system

New research shows that stress accelerates the aging of the immune system and could help explain age-related health disparities.

Traumatic life events and daily stress prematurely weaken the body’s mix of immune cells.

It is widely recognized that as people start getting up over the years, their immune systems weaken. A striking example is the ongoing COVID-19 pandemic, in which the elderly face a much higher mortality rate than the young.

This process of gradual deterioration of the immune system caused by the natural advancement of age is called immunosenescence. Yet you may know people who are quite old, but in excellent health, or vice versa, someone who is relatively young, but still prone to infections. What could explain the differences in the strength of the immune system in people of the same age?

Stress, in the form of traumatic events, work stress, everyday stressors and discrimination, accelerates the aging of the immune system, potentially increasing the risk of cancer, cardiovascular disease, and disease-related infections such as COVID-19

First identified in 2019 in Wuhan, China, Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It has spread globally, resulting in the 2019–20 coronavirus pandemic.

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The research, published yesterday (June 13, 2022) in Proceedings of the National Academy of Sciencesit could help explain age-related health disparities, including the unequal toll of the pandemic, and identify possible intervention points.

“As the world’s elderly population increases, understanding age-related health disparities is essential. Age-related changes in the immune system play a vital role in deteriorating health, “said study lead author Eric Klopack, a postdoctoral fellow at USC Leonard Davis School of Gerontology.” This study helps clarify the mechanisms involved in accelerated immune aging “.

As people age, the immune system naturally begins a dramatic downgrade, a condition called immunosenescence. As we age, a person’s immune profile weakens and includes too many consumed white blood cells in circulation and too few fresh, “naive” white blood cells ready to take on new invaders.

Potential problems related to stress and the immune system

Immune aging is associated not only with cancer but also with cardiovascular disease, increased risk of pneumonia, reduced vaccine efficacy, and organ system aging.

But what explains the drastic health differences in adults of the same age? The USC researchers set out to see if they could pinpoint a connection between life-long exposure to stress – a known contributing factor to poor health – and waning immune system vigor.

“Age-related changes in the immune system play a pivotal role in deteriorating health.” – Eric Klopack

They questioned and compared huge datasets from the University of Michigan Health and Retirement Study, a national longitudinal study of the economic, health, marital, family, and public and private support systems of older Americans.

To measure exposure to various types of social stress, the researchers analyzed the responses of a national sample of 5,744 adults over the age of 50. They responded to a questionnaire designed to assess respondents’ experiences with social stress, including stressful life events, chronic stress, discrimination, and lifetime discrimination.

The participants’ blood samples were then analyzed through flow cytometry, a laboratory technique that counts and classifies blood cells as they pass one by one in a narrow stream in front of a laser.

As expected, people with higher stress scores had apparently older immune profiles, with lower rates of fresh disease fighters and higher percentages of white blood cells consumed. The association between stressful life events and fewer responsive or naive T cells remained strong even after controlling for education, smoking, alcohol use, BMI, race or ethnicity.

Some sources of stress may be impossible to control, but researchers say there may be an alternative solution.

T lymphocytes, a key component of immunity, mature in a gland called the thymus, which is located just in front of and above the heart. As people age, the tissue in their thymus shrinks and is replaced by fatty tissue, resulting in a reduction in the production of immune cells. Previous research suggests that this process is accelerated by lifestyle factors such as poor diet and low exercise, both of which are associated with social stress.

“In this study, after statistically checking for poor diet and low exercise, the connection between stress and accelerated immune aging was not that strong,” said Klopack. “This means that people who experience more stress tend to have poorer diet and exercise habits, partly explaining why they have more accelerated immune aging.”

Stress and the immune system: impact of diet and exercise

Improving diet and exercise in older adults can help offset stress-associated immune aging.

Furthermore, cytomegalovirus (CMV) can be a target for surgery. CMV is a common virus, usually asymptomatic in humans and is known to have a strong effect on accelerating immune aging. Like shingles or cold sores, CMV is dormant most of the time but can become inflamed, especially when a person is experiencing severe stress.

In this study, statistical control of CMV positivity also reduced the connection between stress and accelerated immune aging. Thus, widespread vaccination against CMV could be a relatively simple and potentially powerful intervention that could reduce the effects of stressful immune aging, the researchers said.

Reference: “Social Stressors Associated with Age-Related T-Cell Rates in US Elderly: Evidence from the US Health and Retirement Study” by Eric T. Klopack, Eileen M. Crimmins, Steve W. Cole, Teresa E. Seeman, and Judith E Carroll, June 13, 2022, Proceedings of the National Academy of Sciences.
DOI: 10.1073 / pnas.2202780119

In addition to Klopack, other authors include Eileen Crimmins, a university professor and AARP chair in gerontology at USC Leonard Davis School; and Steve Cole and Teresa Seeman of UCLA.

The study was supported by grants from the National Aging Institute (P30AG017265, U01AG009740).