Stress and trauma early in life have been linked to an increased risk of obesity, cardiovascular disease, and poor mental health later in life. Until now, however, few studies have investigated how trauma early in life affects the immune system. While a significant number of studies have investigated the link between stress and trauma on biomarkers of inflammation, work examining other immune-related biomarkers is lacking.
In the current study, the researchers examined various blood serum measures of immune function, including immune response to cytomegalovirus (CMV). CMV is a kind of herpes virus that is estimated to affect around 80% f people in Europe and North America and 100% of those in Asia and Africa. The virus can be used as a biomarker of immune function as, once contracted, it remains in the body and reactivates under stressful conditions.
"Trauma, you could imagine, likely reactivates it,” said Dr. Grace Noppert, a social epidemiologist at the Survey Research Center in the University of Michigan Institute for Social Research, and one of the study's authors, in a press release. “And so, every time it reactivates, it forces your immune system to expend all of these resources to try to get it to a latent state. It’s costly to the immune system in that way. When you see somebody with high levels of antibodies to CMV, that tells us that your immune system is not dealing with that virus well anymore.”
For the study, the researchers examined data from 5, 823 individuals aged 65 years and older. Data included parental or caregiver death or separation before age 16 years old, response to CMV, as well as other indicators of immune function such as inflammatory markers C-reactive Protein (CRP) and Interleukin-6 (IL-6). It also included racial and ethnic differences.
Ultimately, they found that participants who experienced parental or caregiver loss and separation tended to have poorer immune function later in life. In particular, they found that non-Hispanic Black people who experienced caregiver or parental loss before age 16 had a 26% increase in antibodies for CMV later in life. Meanwhile, non-Hispanic white people underwent a 3% increase in the same antibodies. The results remained after controlling for factors including age, gender, parental education, and other health indicators.
The researchers wrote that while their sample is representative of the US population, their findings may not apply to other populations. They added:
"Moreover, while we observed consistent associations with CMV, immune control of CMV is a dynamic process occurring across the life course and is heavily influenced by the initial infectious dose as well as re-exposure to the virus, a process we could not disentangle with the available data."
Sources: Neuroscience News, PLOS ONE