A new study finds that stressful life events or circumstances are linked to worsening biological health, with financial stress in particular having the greatest adverse effects on the immune, nervous and endocrine systems, which are critical to maintaining good health.

The immune, nervous, and endocrine systems are constantly and actively communicating to maintain homeostasis, the body's self-regulating process for optimal function. This comprehensive network of body systems controls physiological processes such as cell growth and differentiation, metabolism, and human behavior, and when it malfunctions, it can lead to physical and mental illnesses, including cardiovascular disease, depression, and accelerated aging.

Stress, especially chronic stress, is considered a modulator of these systems and their activity. However, scientific evidence on the effects of stress on immuno-neuroendocrine activity in older adults is sparse. So researchers at University College London (UCL) examined longitudinal links between psychological stress and different immune and neuroendocrine profiles in older adults.

"When the immune system and the neuroendocrine system function well together, balance is maintained and health is protected," said Odessa Hamilton, first author and corresponding author of the study. "But chronic stress can disrupt this biological exchange, leading to disease."

Researchers analyzed the levels of four blood biomarkers in 4,934 participants aged 50 and over (median age 65) in the English Longitudinal Study of Aging (ELSA). Two of the biomarkers - C-reactive protein (CRP) and fibrinogen - are involved in the innate immune inflammatory response; the other two biomarkers - cortisol and insulin-like growth factor 1 (IGF-1) - are involved in the physiological process of the stress response.

The researchers used latent signature analysis (LPA), a powerful statistical technique, to identify subgroups of individuals with similar biomarker activity and identify biomarker activity groups that could be divided into three feature groups: healthy low-risk, moderate-risk, and high-risk. They looked at how early exposure to six psychological stressors - financial stress, caregiving, disability, illness, bereavement and divorce - affects the likelihood that people will later be in a high-risk group.

There were 8,083 unique stressful experiences recorded, with many participants experiencing more than one type of stress. Among all participants, 12.5% ​​experienced high levels of stress, and these tended to be younger, female, smokers, and drink less than three drinks per week. In terms of personal stressors, 17% experienced financial stress, 7% were informal caregivers, 45.8% had limited mobility, 31.5% had a long-term localized illness, 40.9% were widowed and 9.2% were divorced.

The researchers found that overall exposure to stress was associated with a 61% increase in the likelihood of being in a high-risk group four years later. The effects are cumulative; with each episode of stress, the likelihood of being at high immuno-neuro-endocrine risk increases by 19%.

Stress related to financial stress was the strongest independent determinant of belonging to the immunological and neuroendocrine high-risk groups, followed by long-term illness and bereavement. Participants who reported only financial stress (i.e., thinking they might not have enough resources to meet future needs) were 59% more likely to be at risk four years later.

The link remained evident after accounting for genetic variation (polygenic markers) for immune and neuroendocrine activity, as well as various demographic, socioeconomic, lifestyle and health factors.

"We found that financial stress is the most harmful to biological health, although more research is needed to determine this," 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 assert a cause-and-effect relationship, they say their findings support the idea that exposure to high levels of stress triggers a complex cascade of physiological events that have previously been linked to disease.

The research was published in the journal Brain, Behavior, and Immunity.