As we age, our immune system begins to decline in performance, a condition called immunosenescence.
This implies an increasing reluctance for older, worn-out white blood cells to withdraw from the circulation, while there are “too few fresh, ‘naive’ white blood cells ready to take on new invaders”.
This ‘aging of the immune system’ has been linked not only to cancer, “but also to cardiovascular disease, increased risk of pneumonia, reduced vaccine efficacy and aging of the organ system”.
While this decline is inevitable, it happens at different rates for different people. Why is that?
A new study finds that stress — in the form of traumatic events, work pressure, everyday stressors and discrimination — is a powerful accelerator of this decline, increasing our risk of serious illness.
Lead study author Eric Klopack, a postdoctoral researcher at the Leonard Davis School of Gerontology at the University of Southern California, said: “As the global population of older adults increases, it is essential to understand the differences in age-related health. Age-related changes in the immune system. play a crucial role in declining health.
“This study helps clarify the mechanisms involved in accelerated immune aging.”
So what was the study?
First, 5744 study participants over the age of 50 answered a questionnaire “designed to assess respondents’ experiences of social stress, including stressful life events, chronic stress, everyday discrimination, and lifelong discrimination.”
Then blood samples from the participants were analyzed by flow cytometry, a lab technique that counts and classifies blood cells as they pass one at a time in a narrow stream in front of a laser.
In other words, the participants’ immune systems were audited by counting the number of worn-out blood cells against the number of fresh and efficient white blood cells.
The researchers specifically examined T cells, a type of white blood cell, which are an essential part of the immune response to viral infections and foreign bodies.
As expected, “people with higher stress scores had an older-looking immune profile, with lower percentages of fresh disease fighters and higher percentages of worn-out white blood cells”.
The researchers say the association between stressful life events and less willing to respond, or naive, T cells “remained strong even after controlling for education, smoking, drinking, BMI, and race or ethnicity.”
More about T cells
T cells mature in the thymus, a gland located behind the breastbone.
As we age, healthy tissue in the thymus is replaced by fatty tissue, resulting in decreased production of immune cells.
The authors of the new study cite previous research showing that this deterioration of the thymus gland and subsequent loss of immune cells is “accelerated by lifestyle factors such as poor diet and little exercise, both of which are associated with social stress.”
“In this study, after being statistically controlled for poor diet and exercise, the association between stress and accelerated aging of the immune system was not as strong,” said Dr. Klopack.
“What this means is that people who experience more stress tend to have poorer eating and exercise habits, which partly explains why they have accelerated immune aging.”
The point is?
Dr Klopack says improving eating and exercise behavior in older adults “may help offset immune aging associated with stress.”
Another potential target for intervention is the cytomegalovirus (CMV), a common, mostly asymptomatic virus in humans “known to have a strong effect in accelerating the aging of the immune system”.
Like shingles or cold sores, CMV is a member of the herpes family and is asleep most of the time.
It can flare up, “especially when someone is under a lot of stress,” and you’ll have a mild flu-like illness for a few days, sometimes weeks.
The authors suggest that widespread CMV vaccination “could be a relatively simple and potentially powerful intervention that could reduce the immune-aging effects of stress.”
Good idea, but there are no vaccines available for CMV.
There is plenty of research and development involved, “with the hope and expectation that it will be available in the next five to ten years.”
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