Stress, in the form of traumatic events, job strain, everyday stressors, and discrimination, accelerates the aging of the immune systemwhat can increase the risk of cancer, cardiovascular disease, and infectious diseases such as COVID-19 of a person, according to a new scientific study.
The investigation, published in the prestigious magazine Proceedings of the National Academy of Sciences (PNAS), could help explain age-related health disparitiesincluding the uneven toll of the pandemic, and identify possible points of intervention.
“As With the global population of older adults increasing, it is essential to understand age-related health disparities. Age-related changes in the immune system play a fundamental role in the deterioration of health. This study helps clarify the mechanisms involved in accelerated immunological aging,” explained lead study author Eric Klopack, a postdoctoral fellow at the University of Southern California (USC), a professor in the Leonard Davis School of Gerontology.
As people age, the immune system naturally begins to undergo drastic degradation, a condition called immunosenescence. With advancing age, a person’s immune profile weakens, including too many worn-out white blood cells circulating and too few fresh “naive” white blood cells ready to take on new invaders. Immune aging is associated not only with cancer, but also with cardiovascular disease, increased risk of pneumonia, decreased efficacy of vaccines, and organ aging.
But, What explains the drastic differences in health in adults of the same age? The USC researchers decided to see if they could uncover a connection between lifetime exposure to stress, a known contributor to poor health, and decreased vigor in the immune system.
For it, consulted and compared huge data sets from the University of Michigan Health and Retirement Study, A national longitudinal survey of the economy, health, marital status, family status, and public and private support systems of older Americans. To estimate exposure to various forms of social stress, the researchers analyzed the responses of a national sample of 5,744 adults over 50 years of age. They answered a questionnaire designed to assess respondents’ experiences with social stress, including stressful life events, chronic stress, everyday life, and discrimination. The participants’ blood samples were then analyzed using flow cytometry, a laboratory technique that counts and sorts 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 immune profiles that seemed higher, with lower percentages of fresh disease fighters and higher percentages of worn-out white blood cells. The association between stressful life events and fewer T cells ready to respond, or naïve, remained strong even after controlling for education, smoking, drinking, BMI, and race/ethnicity. Some sources of stress can be impossible to control, but researchers say there may be a solution.
T cells, a critical 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 thymus tissue 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 such as poor diet and lack of exercise, which are associated with social stress. “In this study, after statistically controlling for poor diet and lack of exercise, the connection between stress and accelerated immune aging was not as strong,” Klopack said.
“What this means is that people who experience more stress tend to have poorer diet and exercise habits, which partly explains why they have more accelerated immune aging.” Improving diet and exercise behaviors in older adults may help offset immune aging associated with stress.
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 it can come back, especially when a person is experiencing a lot of stress.
In this study, statistical control for CMV positivity also reduced the connection between stress and accelerated immune aging. Therefore, widespread CMV vaccination could be a relatively simple and potentially powerful intervention that could reduce the effects of stress on immune aging, the researchers said.