Stress accelerates aging of the immune system, increasing risk of cancer and heart disease

LOS ANGELES — Stress can prematurely weaken the body’s immune system, putting people at greater risk of cancer, heart attacks, and infections like COVID, a new study warns.

Researchers from USC found that traumatic events accelerate the aging of the immune system, potentially increasing a person’s risk of developing a whole range of illnesses, including cardiovascular disease. The team’s findings, published in the Proceedings of the National Academy of Sciences (PNAS), could help explain disparities in age-related health, including the greater toll of the COVID-19 pandemic on the elderly.

“As the world’s population of older adults increases, understanding disparities in age-related health is essential. Age-related changes in the immune system play a critical role in declining health,” says study lead author Dr. Eric Klopack in a university release. “This study helps clarify mechanisms involved in accelerated immune aging.”

As people age, the immune system naturally begins to deteriorate, a condition called immunosenescence. With advanced age, Dr. Klopack explains that too many worn-out white blood cells continue to circulate, while too few fresh white blood cells are ready to take on new invaders.

Everyday stressors can lead to fewer T cells

Immune system aging not only has a connection to cancer development, but also to cardiovascular disease, increased risk of pneumonia, reduced efficacy of vaccines, and organ system aging. The USC researchers wanted to find a connection between lifetime exposure to stress – a known contributor to poor health – and declining performance of the immune system.

They examined and cross-referenced data from the University of Michigan’s Health and Retirement Study of the economic, well-being, marital, family status, and public and private support systems of older Americans during their new study.

To calculate exposure to various forms of social stress, the team analyzed responses from a national sample of more than 5,700 adults over the age of 50. The participants answered a questionnaire designed to assess respondents’ experiences with social stress, including stressful life events, chronic stress, everyday discrimination, and lifetime discrimination.

They also analyzed blood samples from the participants through flow cytometry, a lab 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 older immune profiles, with lower percentages of fresh disease fighters and higher percentages of worn-out white blood cells.

Dr. Klopack says the link between stressful life events and fewer T cells remained strong even after the team accounted for each person’s level of education, smoking and drinking habits, BMI, and race or ethnicity. Some sources of stress may be impossible to control, but the researchers say there may be a workaround.

Could a vaccine for one virus fix this?

T-cells, which are critical for fighting off infections, mature in the thymus gland, which sits just in front of the heart. As people age, the tissue in their thymus shrinks and fatty tissue replaces it. This leads to a reduced production of immune cells. Previous studies have found that this process accelerates if people have a poor diet and don’t exercise.

“In this study, after statistically controlling for poor diet and low exercise, the connection between stress and accelerated immune aging wasn’t as strong,” Klopack says. “What this means is people who experience more stress tend to have poorer diet and exercise habits, partly explaining why they have more accelerated immune aging.”

The team adds that improving diet and exercise habits among older adults may help offset the immune aging process tied to stress. Additionally, Klopack says cytomegalovirus (CMV) may be a target for intervention.

Study authors note CMV is a common, typically asymptomatic virus that can have a strong influence on accelerated immune aging. Like shingles or cold sores, CMV can stay dormant for long periods of time before it flares up, especially when a person is experiencing stress. In the new study, controlling for CMV positivity reduced the connection between stress and accelerated immune aging. Therefore, vaccinating for CMV could be a relatively simple way to reduce the immune aging effects of stress.

South West News Service writer Jim Leffman contributed to this report.

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