A collaborative long-term study between University College London (UCL), University of California San Francisco and Cardiff Metropolitan University has uncovered new findings that indicate people's physiological responses to stress can accelerate the ageing process of their cells.
The results could have wider implications for understanding how psychosocial and environmental factors influence biological ageing.
Led by Professor Andrew Steptoe from UCL, the research team studied 411 participants over a three-year period to examine the link between their 'white blood cell telomere length' and cortisol responses to acute mental stress testing.
What are telomeres?
Telomeres are 'caps' situated at the ends of each chromosome that protect the genomic DNA of animal and plant cells. Telomeres shorten with each cell division, and telomere length is a measure of the ageing of cells in our bodies. The function of telomeres can be impaired if the shortening becomes critical and in humans this has been associated with increased risk of cardiovascular disease, cancer, diabetes and dementia.
There is also growing evidence that shorter telomeres are associated with psychiatric conditions and psychological stress. Because of this, the researchers wanted to have a better understanding of the potential underlying physiological mechanisms that may accelerate shortening of telomeres as a result of stress exposure.
What role does cortisol play during mental stress?
Cortisol is a steroid hormone, which is made in the adrenal glands, and then released into the blood to be transported around the body.
Almost every cell contains receptors for cortisol and the hormone can have different actions depending on which kind of cells it is acting upon.
The adrenal glands produce more cortisol in response to stress and because of this and its multiple effects on immune, metabolic and cardiovascular functions, cortisol plays a central role in stress responses.
Previous scientific studies have suggested that larger cortisol responses to mental stress tests are associated with having shorter telomeres; however, these studies have examined associations at a single point in time rather than looking at effects over a period of time.
Who were the participants and how were they tested?
The participants were healthy men and women aged 54-76 from across a wide range of socioeconomic backgrounds who were drawn from a long-term epidemiological study looking at socio-economic determinants of health among British civil servants.
The research team administered two behavioural tests to induce mild stress in the participants, similar to that elicited when confronted with everyday life challenges. The participants gave saliva samples before and after the mental stress tests as well as blood samples at the time of the test and three years later.
The saliva samples were used by the researchers to establish by how much the participants' cortisol levels changed as a result of the tasks; and according to the results split them into two groups, 'cortisol responders' and 'non-responders'.
The blood samples were used to measure the lengths of the telomeres in the white blood cells enabling to estimate by how much these shortened over the three year period. The researchers then looked if there were differences in the degree of telomere attrition over time between the cortisol-responder and the non-responders.
What were the findings?
The key finding from the research is that participants who were grouped as cortisol responders had shorter telomeres and more rapid telomere attrition after the three-year period than non-responders. This association remained significant even after taking into account sociodemographic and physiological factors that might also affect telomere length.
The researchers estimated that the difference equated to approximately two years in cellular ageing.
Cardiff Metropolitan University's Professor of Biomedical Sciences Dr Jorge Erusalimsky, who co-authored the paper, said:
"The findings of this study expand our understanding of the biological mechanisms through which psychosocial factors and mental health may affect the ageing process, highlighting the role that cortisol responsivity may play on the preservation of telomere integrity. That excessive stress, regardless of its origin, has negative effects on human biology and health is not a new concept. The importance of the present findings lies in that they suggest that variability among individuals in their physiological response to stress impacts on their rate of cellular ageing, and therefore that interventions that could attenuate this response could slow the ageing process."
The study was published in the Journal of Clinical Endocrinology and Metabolism.