The study, which was released on June 13 in the Proceedings of the National Academy of Sciences (PNAS), may help explain differences in aging-related health, such as the unequal impact of the pandemic, and it may also indicate to potential intervention locations.
A recent USC study found that stress may potentially raise a person’s risk of developing cancer, cardiovascular disease, and infections like COVID-19. Immunosenescence is the term for the natural substantial decline in immune function that occurs as we age.
An individual’s immune profile deteriorates with age and becomes characterized by an excess of exhausted white blood cells in circulation and a deficiency of young, “naive,” white blood cells prepared to fight off incoming intruders.
In addition to cancer, immune aging is linked to cardiovascular disease, a higher risk of pneumonia, decreased vaccine effectiveness, and aging of the organ systems. But why do adults of the same age have such disparate levels of health? Researchers at USC chose to investigate whether there is a link between a lifetime of stress, which is known to be detrimental to health, and a deteriorating immune system.
Large data sets from the University of Michigan’s Health and Retirement Research, a longitudinal nationwide study of older Americans’ economic, health, marital, and familial statuses as well as their access to public and private support networks, were searched and cross-referenced. The researchers examined responses from a national sample of 5,744 persons over 50 to determine exposure to various types of social stress.
They responded to a survey meant to gauge respondents’ exposure to social stress, which can include stressful life events, chronic stress, daily discrimination, and lifetime discrimination. The individuals’ blood samples were subsequently subjected to flow cytometry analysis, a laboratory procedure that counts and categorizes blood cells as they move sequentially through a restricted stream in front of a laser.
As expected, those with higher stress levels had immunological profiles that seemed older, with higher percentages of worn-out white blood cells and lower percentages of young disease fighters. Even after accounting for factors including education, smoking, drinking, BMI, and race or ethnicity, the relationship between stressful life events and less ready to respond, or naïve, T cells remained significant.
Although the researchers acknowledge that some stressors may be insurmountable, there may be a solution. A gland called the thymus, which is located directly in front of and above the heart, is where T-cells, an essential part of immunity, develop. People’s thymus tissue diminishes and is replaced with fatty tissue as they age, which lowers the number of immune cells produced. According to prior study, lifestyle factors including a poor diet and little exercise—both of which are connected to social stress—accelerate this process.
“In this study, after statistically controlling for poor diet and low exercise, the connection between stress and accelerated immune aging wasn’t as strong,” said Klopack. “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.”
Additionally, cytomegalovirus (CMV) may be a target for intervention. CMV is a common, usually asymptomatic virus 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 flare up, especially when a person is experiencing high stress.
The immunological aging brought on by stress may be prevented in older persons by improving diet and exercise habits. In this investigation, the association between stress and accelerated immunological aging was diminished by statistically adjusting for CMV positive. Therefore, the researchers suggested that universal CMV immunization could be a reasonably easy and potentially effective strategy that could lessen the immunological aging consequences of stress.
Parvathy Sukumaran 
