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As they age, their immune systems naturally begin to weaken. This aging of the immune system, called immunosenescence, may be an important part of age-related health problems such as cancer and cardiovascular disease, as well as the elderly’s less effective response to vaccines.
But not all immune systems age at the same rate. In our recently published study, my colleagues and I found that social stress—stress resulting from difficult or challenging circumstances related to your social standing or relationships with other people—is associated with signs of accelerated aging of the immune system.
Data and immunosequencing
To better understand why people of the same chronological age can have different immunological ages, my colleagues and I looked at data from the Study on Health and Retirement, a large, nationally representative survey of US adults over age 50 funded by the National Institute on Aging.
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HRS researchers asked participants about different types of stressors they had experienced, including stressful life events such as job loss; discrimination, which may mean unfair treatment or denial of care; a major lifetime trauma, such as a family member’s life-threatening illness; and chronic stress, such as financial strain.
Recently, HRS researchers also began collecting blood from a sample of participants, counting the number of different types of immune cells present, including white blood cells. These cells play a central role in immune responses against viruses, bacteria and other invaders. This is the first time such detailed information about immune cells has been collected in a large national study.
Analyzing data from 5,744 HRS participants who donated blood and answered survey questions about stress, my research team and I found that people who had experienced more stress had a lower proportion of “naïve” T cells—fresh cells needed to deal with invaders. the immune system has not encountered before.
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They also had a greater proportion of “lately differentiated” T cells — older cells that have exhausted their ability to fight invaders and instead produce proteins that can increase harmful inflammation.
People with low proportions of newer T cells and high proportions of older T cells have an older immune system.
After controlling for poor diet and low exercise, however, the link between stress and accelerated immune system aging was not as strong. This suggests that improving these healthy behaviors may help offset the dangers associated with stress.
Likewise, after we accounted for potential exposure to cytomegalovirus (CMV)—a common, usually asymptomatic virus known to accelerate immune system aging—the link between stress and immune cell aging was attenuated. Although CMV usually remains latent in the body, researchers have found that stress can cause CMV to flare up and force the immune system to devote more resources to controlling the reactivated virus. Sustained infection control can deplete naïve T cell stores and lead to more exhausted T cells circulating in the body and causing chronic inflammation, an important factor in age-related diseases.
Understanding Immune Aging
Our study helps clarify the link between social stress and faster aging of the immune system. It also highlights potential ways to slow the aging of the immune system, such as changing the way people cope with stress and improving lifestyle behaviors around diet, smoking and exercise. The development of effective vaccines against cytomegalovirus may also help alleviate the aging of the immune system.
Strengthening your immunity as you age
However, epidemiological studies cannot fully establish cause and effect. More research is needed to confirm whether stress reduction or lifestyle changes will lead to improvements in the aging immune system and to better understand how stress and latent pathogens such as cytomegalovirus interact to cause disease and death. We use additional data from the HRS to examine how these and other factors—including childhood adversity—affect immune aging over time.
Less aged immune systems are better able to fight infections and generate protective immunity from vaccines. Immunosenescence may help explain why people are likely to have more severe cases of the coronavirus and a poorer response to vaccines as they age. Understanding what influences immune aging may help researchers better address age-related differences in health and disease.
This article was originally published on theconversation.com.
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