Cumulative Life Course Effects on Aging and Health in a Long-Lived Primate Model

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PROJECT SUMMARY Life course theory emphasizes that aging is a trajectory that starts early in life, and as such, individual heterogeneity in aging is rooted in a lifetime of health exposures and the environments in which we live. This perspective is critical for understanding the nature and modifiability of health inequalities among the aged. However, it has been extraordinarily difficult to put life course perspectives into practice, owing to the long timeframes necessary to study humans and the difficulty of operationalizing relevant features of human environments. We propose that these problems can be rectified by studying an underused model system, chimpanzees. This research extends a longitudinal study aimed at investigating the biology of aging in chimpanzees, one of our closest living relatives and a critical link for reconstructing how the human aging process evolved. This close evolutionary relationship results in genetic and physiological similarities that are not represented by common laboratory animal models. Chimpanzees are socially-complex and long-lived, meaning that they are particularly well suited to study how environmental factors such as the chronic burden of infection, social support, and social inequality yield health effects across a lifetime. In our first funding period, we validated a robust toolkit of non-invasive biomarkers of health and aging and used longitudinal sampling of chimpanzees to establish how the chimpanzee aging process compares with humans. In the renewal period, we build on those successes by addressing the multidimensionality of our longitudinal health data. Aim 1 will extend the longitudinal health monitoring and biosampling of our original sample and increase the sample to a total of 350 wild and 200 free-ranging chimpanzees. We will also develop accessible resources for comparative aging research. Aim 2 will examine the hypothesis that the cumulative burden of infection across life is a significant determinant of individual heterogeneity in aging. The immune system plays a pivotal role in the aging process and has complex feedbacks on other aspects of senescence. Yet, the long lifespans of humans evolved in environments where infectious challenges to the immune system were persistent. In wild chimpanzees, we can study these dynamics in a system without medical intervention and where other age- related pathologies are rare. Aim 3 builds upon Aim 2 by examining the hypothesis that social processes modify aging trajectories. We are particularly interested in understanding the mechanisms by which social support and status from early adulthood, when they are first established, contribute to later life health disparities, and whether these impacts can be further modified by age-related shifts in social behavior. Chimpanzees in our study populations have been closely observed for most or all of their adult lives, providing a rare opportunity to apply objective, detailed social histories to the study of aging in the absence of major lifestyle factors that complicate human studies.