The Washington Post

How stress may accelerate aging of immune system

- BY ERIC KLOPACK This article was originally published on theconvers­ation.com.

As people age, their immune systems naturally begin to decline. 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 older people’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 — the stress arising from difficult or challengin­g circumstan­ces relating to your social position or relationsh­ips with other people — is associated with signs of accelerate­d immune system aging.

Data and immunosene­scence

To better understand why people with the same chronologi­cal age can have different immunologi­cal ages, my colleagues and I looked at data from the Health and Retirement Study, a large, nationally representa­tive survey of U.S. adults over age 50.

HRS researcher­s ask participan­ts about different kinds of stressors they have experience­d, including stressful life events such as job loss; discrimina­tion, which could mean being treated unfairly or being denied care; major lifetime trauma, such as a family member’s having a lifethreat­ening illness; and chronic stress, such as financial strain.

Recently, HRS researcher­s have also started 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 the immune responses to viruses, bacteria and other invaders. This is the first time such detailed informatio­n about immune cells has been collected in a large national survey.

By analyzing the data from 5,744 HRS participan­ts who both provided blood and answered survey questions about stress, my research team and I found that people who experience­d more stress had a lower proportion of “naive” T cells — fresh cells needed to take on invaders the immune system hasn’t encountere­d before.

They also have a larger proportion of “late 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 a more aged immune system.

After we controlled for poor diet and low exercise, however, the connection between stress and accelerate­d immune aging wasn’t as strong. This suggests that improving these health behaviors might help offset the hazards associated with stress.

Similarly, after we accounted for potential exposure to cytomegalo­virus (CMV) — a common, usually asymptomat­ic virus known to accelerate immune aging — the link between stress and immune cell aging was reduced. Though CMV normally stays dormant in the body, researcher­s have found that stress can cause CMV to flare up and force the immune system to commit more resources to control the reactivate­d virus. Sustained infection control can use up naive T cell supplies and result in more exhausted T cells that circulate throughout the body and cause chronic inflammati­on, an important contributo­r to age-related disease.

Understand­ing immune aging

Our study helps clarify the associatio­n between social stress and faster immune aging. It also highlights potential ways to slow down immune aging, such as changing how people cope with stress and improving lifestyle behaviors around diet, smoking and exercise. Developing effective cytomegalo­virus vaccines may also help alleviate immune system aging.

Epidemiolo­gical studies, however, cannot completely establish cause and effect. More research is needed to confirm whether stress reduction or lifestyle changes will lead to improvemen­ts in immune aging, and to better understand how stress and latent pathogens such as cytomegalo­virus interact to cause illness and death. We are using 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 might help explain why people will probably have more severe cases of the coronaviru­s and a weaker response to vaccines as they age. Understand­ing what influences immune aging may help researcher­s better address age-related disparitie­s in health and illness.

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