People's immune systems gradually deteriorate as they become older. Immunosenescence, or the aging of the immune system, may have a role in age-related health issues including cancer and cardiovascular disease, as well as older people's less effective vaccination response.
However, immune systems do not all mature at the same rate. My colleagues and I recently released a study that indicated that social stress is linked to indicators of accelerated immune system aging.
Stress and immunosenescence
My colleagues and I looked at data from the Health and Retirement Study (HRS), a large, nationally representative study of US individuals over 50, to better understand why persons of the same chronological age might have varied immunological ages.
Stressful life events, such as job loss; discrimination, such as being treated unjustly or denied care; substantial lifetime trauma, such as a family member's life-threatening illness; and chronic stress, such as financial hardship, are among the stressors that HRS researchers question participants about.
HRS researchers have recently begun taking blood samples from a group of individuals and quantifying the quantity of different types of immune cells present, including white blood cells. Immune responses to viruses, bacteria, and other invaders rely heavily on these cells. This is the first time a major nationwide study has gathered such precise information on immune cells.
My research team and I discovered that people who experienced more stress had a lower proportion of "naive" T cells – fresh cells needed to take on new invaders the immune system hasn't encountered before – by analyzing data from 5,744 HRS participants who both provided blood and answered survey questions about stress.
They also contain a higher percentage of "late differentiated" T cells, which are older cells that have lost their capacity to combat intruders and instead create proteins that might worsen inflammation. A person's immune system is more elderly if they have a low proportion of fresh T cells and a high number of older T cells.
The link between stress and accelerated immunological aging was less once we accounted for poor nutrition and lack of exercise. This shows that enhancing these health practices might help mitigate the risks of stress.