According to a new study from USC, 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, diseases cardiovascular diseases and diseases due to infections such as COVID-19. .
The research, published Monday in the Proceedings of the National Academy of Sciencescould help explain age-related health disparities, including the uneven toll of the pandemic, and identify possible points of intervention.
“As the global population of older adults grows, understanding age-related health disparities is critical. Age-related changes in the immune system play a critical role in health decline,” said study lead author Eric Klopack, a postdoctoral researcher at the 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 to deteriorate dramatically, a condition called immunosenescence. With advancing age, a person’s immune profile weakens to include too many spent white blood cells in circulation and too few fresh, “naïve” white blood cells ready to deal with 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 effectiveness, and organ system aging.
But what explains the drastic health differences among adults of the same age? The USC researchers set out to see if they could establish a link between lifetime exposure to stress – a known contributor to poor health – and declining immune system vigor.
They interrogated and cross-referenced huge datasets from the University of Michigan Health and Retirement Studya 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 completed a questionnaire designed to assess respondents’ experiences of social stress, including stressful life events, chronic stress, discrimination, and lifelong discrimination.
Blood samples from the participants were then analyzed using flow cytometry, a laboratory technique that counts and classifies blood cells as they pass one by one in a narrow stream past a laser.
As expected, people with higher stress scores had older immune profiles, with lower percentages of new disease fighters and higher percentages of worn-out white blood cells. The association between stressful life events and fewer responsive or naïve T cells remained strong even after controlling for education, smoking, alcohol, BMI, and race or gender. ‘Ethnicity.
Some sources of stress can be impossible to control, but researchers say there may be a workaround.
T cells – an essential component of immunity – mature in a gland called the thymus, which sits just in front and above the heart. As people age, the tissue in their thymus shrinks and is replaced by fatty tissue, which reduces the production of immune cells. Previous research suggests that this process is accelerated by lifestyle factors like poor diet and low exercise, both of which are associated with social stress.
“In this study, after statistically controlling for poor diet and low exercise, the link between stress and accelerated immune aging was not as strong,” Klopack said. “This means that people who experience more stress tend to have poorer eating and exercise habits, which partly explains why they have more accelerated immune aging.”
Stress and the immune system: impact of diet and exercise
Improving dietary and exercise habits in older adults may help offset stress-associated immune aging.
Additionally, cytomegalovirus (CMV) may be a target for intervention. CMV is a common virus, usually asymptomatic in humans and is known to have a strong effect of accelerating immune aging. Like shingles or cold sores, CMV is dormant most of the time, but can flare up, especially when a person is under high stress.
In this study, statistical control for CMV positivity also reduced the link between stress and accelerated immune aging. Therefore, widespread vaccination against CMV could be a relatively simple and potentially powerful intervention that could reduce the effects of stress on immune aging, the researchers said.
In addition to Klopack, other authors include Eileen Criminals, university professor and holder of the AARP chair in gerontology at the USC Leonard Davis School; and Steve Cole and Teresa Seeman of UCLA.
The study was supported by grants from the National Institute on Aging (P30AG017265, U01AG009740).
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