A new study has found that while exposure to stressful life events or circumstances was associated with worse biological health, experiencing financial strain, in particular, had the strongest detrimental effect on the immune, nervous, and endocrine systems that, together, are crucial for maintaining good health.
The immune, nervous, and endocrine systems actively and constantly communicate to maintain homeostasis, the self-regulating process by which the body achieves optimal functioning. This integrative network of bodily systems controls physiological processes such as cell growth and differentiation, metabolism, and human behavior, and when it doesn’t work, it can lead to physical and mental illnesses, including cardiovascular disease, depression, and accelerated aging.
Stress, especially chronic stress, has been implicated as a modulator of these systems and their activities. However, there’s little scientific evidence on the effect of stress on immune-neuroendocrine activity in older adults. So, researchers from University College London (UCL) looked at the longitudinal association between psychological stress and distinct immune and neuroendocrine profiles amongst that population.
“When the immune and neuroendocrine systems function well together, homeostasis is maintained, and health is preserved,” said Odessa Hamilton, lead and corresponding author of the study. “But chronic stress can disrupt this biological exchange and lead to disease.”
The researchers analyzed levels of four blood biomarkers in 4,934 people aged 50 and over (median age 65) who were participants in the English Longitudinal Study of Ageing (ELSA). Two biomarkers – C-reactive protein (CRP) and fibrinogen – are involved in the innate immune response to inflammation; the other two – cortisol and insulin-like growth factor 1 (IGF-1) – in the physiology of the stress response.
Using latent profile analysis (LPA), a powerful statistical technique that enabled the researchers to identify subgroups of individuals with similar biomarker activity, they identified clusters of biomarker activity that fell into three profile groups: low risk to health, moderate risk, and high risk. They looked at how early exposure to six psychological stressors – financial strain, caregiving, disability, illness, bereavement, and divorce – might affect people’s subsequent likelihood of being in the high-risk group.
There were 8,083 unique documented stress experiences, with many participants experiencing more than one stressor. Of all participants, 12.5% experienced a high level of stress, and this group tended to be younger, female, smokers, and drank less than three alcoholic drinks a week. Regarding individual stressors, 17% experienced financial strain, 7% were informal carers, 45.8% had difficulty mobilizing, 31.5% had a limiting longstanding illness, 40.9% were bereaved, and 9.2% were divorcees.
The researchers found that exposure to stressors overall was linked to a 61% increase in the likelihood of belonging to the high-risk group four years later. The effect was cumulative; for each stressor experienced, individuals were 19% more likely to be in the high-risk immune-neuroendocrine profile.
Stress associated with financial strain was the strongest independent determinant of belonging to the high-risk immune and neuroendocrine profile, followed by limiting longstanding illness and bereavement. Participants who only reported financial strain, the perception they might not have enough resources to meet future needs, were 59% more likely to belong to the high-risk group four years later.
Associations remained significant after accounting for genetic variants (polygenic markers) of immune and neuroendocrine activity and various demographic, socioeconomic, lifestyle, and health factors.
“We found that financial stress was most detrimental to biological health, although more research is needed to establish this for certain,” Hamilton said. “This may be because this form of stress can invade many aspects of our lives, leading to family conflict, social exclusion, and even hunger or homelessness.”
While the researchers cannot claim causality, they say their results support the idea that exposure to high levels of stress can set off a cascade of complex physiological events that have previously been linked to illness.
The study was published in the journal Brain, Behavior, and Immunity.
Source: UCL
