“People with higher stress scores had older-seeming immune profiles, with lower percentages of fresh disease fighters and higher percentages of worn-out T-cells,” Klopack said.
In addition to finding that people who reported higher stress levels had more zombie cells, Klopack and his team found they also had fewer “naive” T cells, which are the young, fresh cells needed to take on new invaders.
“This paper adds to findings that psychological stress on one hand, and well-being and resources on the other hand, are associated with immunological aging,” said clinical psychologist Suzanne Segerstrom, who was not involved with the study.
Segerstrom, a professor of developmental, social and health psychology at the University of Kentucky in Lexington, has studied the connection between self-regulation, stress and immune function.
“In one of our newer studies … older people with more psychological resources had ‘younger’ T cells,” Segerstrom said.
Poor health behaviors
People in the study were asked questions about their levels of social stress, which included “stressful life events, chronic stress, everyday discrimination and lifetime discrimination,” Klopack said. Their responses were then compared with levels of T-cells found in their blood tests.
“It’s the first time detailed information about immune cells has been collected in a large national survey,” Klopack said. “We found older adults with low proportions of naive cells and high proportions of older T cells have a more aged immune system.”
The study found the association between stressful life events and fewer naive T cells remained strong even after controlling for education, smoking, drinking, weight and race or ethnicity, Klopack said.
However, when poor diet and a lack of exercise were taken in account, some of the connection between social stress levels and an aging immune system disappeared.
That finding indicates that how much our immune system ages when we are stressed is under our control, Klopack said.
How stress affects the brain
As stress hormones flood the body, neural circuitry in the brain changes, affecting our ability to think and make decisions, experts say. Anxiety rises and mood may change. All of these neurological changes impact the whole body, including our autonomic, metabolic and immune systems.
McEwen, who made the landmark 1968 discovery that the brain’s hippocampus can be changed by stress hormones like cortisol, passed away in 2020 after 54 years of researching neuroendocrinology at The Rockefeller University in New York City.
“Being ‘stressed out’ may also cause us to neglect seeing friends, or to take time off from our work, or reduce our engagement in regular physical activity as we, for example, sit at a computer and try to get out from under the burden of too much to do,” McEwen wrote.