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It's a baboon's life

Photo by sk on Unsplash

The stress response is hardwired into the primate genome. Clearly, the acute stress response is critical for the survival of the fittest. In comparison, a chronic stress response comes at a price. Some people like to think of stress as some subjective phenomenon that you measure on a Lickert scale from 0 (no stress) to 7 (severe or intolerable stress). However, the stress response is biological with glucocorticoid production being the biomarker of choice for measuring stress; i.e. the area-under-the-cortisol-curve over time is how we measure chronic stress.

In the field study below of female baboons, chronic glucocorticoid exposure predicted life expectancy. A hypothetical female who maintained glucocorticoid levels in the top decile for her age across adulthood would be expected to lose 5.4 years of life relative to a female who maintained glucocorticoid in the bottom decile for her age. With the life expectancy of the average baboon being 35-45 years of age 5.4 years is a massive reduction in expected life expectancy.

Why is this study so important? Firstly, this is the first time scientists have been shown the effect of chronic stress on life expectancy outside the laboratory in a primate. Secondly, this has relevance to humans and probably explains why social determinants of health and inequality reduce life expectancy. If you are poor, relatively unskilled, with low health literacy and are worried about stable accommodation and food security you are going to be chronically stressed. This is well studied. Similarly, even if you are in the top decile when it comes to deprivation and you live in an unequal society it causes chronic stress. Yes, the more unequal a society the more stressed-out it is; a disharmonious society is a stressed society. This is why the area-under-the-cortisol-curve of the UK population will almost certainly be much greater than that in the Nordic countries or Japan for example.

The question we should all ask ourselves is how do we at a societal or population level reduce our area-under-the-cortisol-curve? This is more than a preventive medicine or public health challenge and requires political will and good policy and is well-rehearsed by people who know about real politics.

If you are interested in reading more about this topic I would suggest reading Michael Marmot’s book ‘The Status Syndrome: How Social Standing Affects Our Health and Longevity’ and Kate Pickett and Richard Wilkinson’s ‘The Spirit Level’. Trust me if you read these books you will never be the same person again.

Campos et al. Glucocorticoid exposure predicts survival in female baboons. Science Advances 21 Apr 2021: Vol. 7, no. 17, eabf6759

Are differences in hypothalamic-pituitary-adrenal (HPA) axis activation across the adult life span linked to differences in survival? This question has been the subject of considerable debate. We analyze the link between survival and fecal glucocorticoid (GC) measures in a wild primate population, leveraging an unusually extensive longitudinal dataset of 14,173 GC measurements from 242 adult female baboons over 1634 female years. We document a powerful link between GCs and survival: Females with relatively high current GCs or high lifelong cumulative GCs face an elevated risk of death. A hypothetical female who maintained GCs in the top 90% for her age across adulthood would be expected to lose 5.4 years of life relative to a female who maintained GCs in the bottom 10% for her age. Hence, differences among individuals in HPA axis activity provide valuable prognostic information about disparities in life span.

Conflicts of Interest

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Disclaimer: Please note that the opinions expressed here are those of Professor Giovannoni and do not reflect the position of the Barts and The London School of Medicine and Dentistry nor Barts Health NHS Trust.
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