As people get older, their immune systems naturally begin to decline. This aging of the immune system, called immunosensitivity, can be an important part of age-related health problems, such as cancer and cardiovascular disease, as well as less effective responses of older people to vaccines.
However, not all immune systems work at the same rate. In a recently published study, my colleagues and I found that social stress is associated with signs of rapid aging of the immune system.
Stress and immunity
To better understand why people of a chronological age may have different immunological ages, my colleagues and I looked at data from the Health and Retirement Survey (HRS), a large survey involving the national representation of U.S. adults over 50 years of age.
HRS researchers asked participants about various stressful life experiences they experienced, including unemployment; discrimination such as unfair treatment or denial of care; life-threatening injuries, such as a life-threatening illness of a family member; and chronic stress, such as financial stress.
Recently, HRS researchers began collecting blood from a sample of participants, counting the number of different types of immune cells, including white blood cells. These cells play a central role in the immune response against viruses, bacteria and other invaders. Such detailed information about these immune cells was collected for the first time in a large national survey.
By analyzing data from 5,744 HRS participants who donated blood and responded to stress survey questions, my research team and I found that people who experienced more stress had a lower proportion of “naive” T cells – new cells to accept new invaders. The immune system has not encountered it before.
They also have a greater proportion of “late differentiated” T cells – older cells that produce proteins that deplete their ability to fight invaders and instead intensify harmful inflammation. The proportion of new T cells is low and the proportion of older T cells is high.
When we controlled poor nutrition and little exercise, the link between stress and accelerated immune aging was less strong. This suggests that improving health-related behaviors can help eliminate stress-related risks.
Similarly, when we consider the potential effects of cytomegalovirus – a virus that is generally asymptomatic, usually accelerates immune aging – the link between stress and the aging of immune cells is reduced.
Although CMV is normally dormant in the body, researchers have found that stress exacerbates CMV and forces the immune system to expend more resources to control the reactivated virus.
Sustained infection control can use up pure T-cell stocks and lead to the death of T-cells that circulate throughout the body, causing chronic inflammation, an important factor in age-related disease.
Understanding Immune Aging
Our study will help clarify the link between social stress and faster immune aging. It also highlights potential ways to slow down immune aging, such as changing people’s way of coping with stress and improving lifestyle behaviors such as diet, smoking and exercise.
The development of effective cytomegalovirus vaccines can also help ease the aging of the immune system.
It is important to note that epidemiological studies cannot fully determine the cause and effect. More research is needed to confirm whether reducing stress or lifestyle changes can improve immune aging, and to better understand how latent pathogens such as stress and cytomegalovirus interact and cause disease and death.
We are currently using additional data from the Health and Retirement Study to study how these and other factors affect immune aging over time as childhood complications.
Younger immune systems are better able to fight infections and build up immune defenses against vaccines. Immunosensitivity can help explain why people develop COVID-19 disease and their reaction to vaccines may worsen with age.
Understanding the effects of immune aging will help researchers better address age-related disparities in health and disease.
Eric Klopack, Postdoctoral Fellow in Gerontology, University of Southern California.
This article was reprinted from The Conversation magazine under a Creative Commons license. Read the original article.