AI Article Synopsis

  • Cortisol, a stress-related hormone, significantly impacts aging and is regulated by the hypothalamic-pituitary-adrenal (HPA) axis, which changes with age.
  • This study analyzed urinary cortisol levels in wild chimpanzees over 20 years to understand aging effects, revealing that older chimpanzees exhibited a blunted daily cortisol rhythm and higher average cortisol levels, regardless of sex.
  • The research suggests that aging in chimpanzees shares similarities with humans in terms of stress response regulation, indicating that these changes are fundamental to aging in hominids, not just due to human factors or environments.

Article Abstract

Cortisol, a key product of the stress response, has critical influences on degenerative aging in humans. In turn, cortisol production is affected by senescence of the hypothalamic-pituitary-adrenal (HPA) axis, leading to progressive dysregulation and increased cortisol exposure. These processes have been studied extensively in industrialized settings, but few comparative data are available from humans and closely related species living in natural environments, where stressors are very different. Here, we examine age-related changes in urinary cortisol in a 20-y longitudinal study of wild chimpanzees ( = 59 adults) in the Kanyawara community of Kibale National Park, Uganda. We tested for three key features of HPA aging identified in many human studies: increased average levels, a blunted diurnal rhythm, and enhanced response to stressors. Using linear mixed models, we found that aging was associated with a blunting of the diurnal rhythm and a significant linear increase in cortisol, even after controlling for changes in dominance rank. These effects did not differ by sex. Aging did not increase sensitivity to energetic stress or social status. Female chimpanzees experienced their highest levels of cortisol during cycling (versus lactation), and this effect increased with age. Male chimpanzees experienced their highest levels when exposed to sexually attractive females, but this effect was diminished by age. Our results indicate that chimpanzees share some key features of HPA aging with humans. These findings suggest that impairments of HPA regulation are intrinsic to the aging process in hominids and are side effects neither of extended human life span nor of atypical environments.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7165472PMC
http://dx.doi.org/10.1073/pnas.1920593117DOI Listing

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