A professor at the University of Southern California has proposed that longevity researchers expand their toolkit to include social hallmarks of aging . This paper is one of a trio that offer a fresh perspective on geroscience by trying to integrate findings from a biological approach into the complex dynamics of humans as social animals.
A framework for longevity research
In a 2013 Cell paper , researchers at several European research institutes proposed a list of nine hallmarks of aging. The perspective provided by the hallmarks helped bring together different strands of longevity research into a coherent, interconnected framework which could guide further research in the field. While researchers have proposed expanding or completely revising the list of hallmarks , the underlying goal continues to be to approach aging as a set of intertwined molecular and cellular changes.
This paradigm has helped longevity researchers make remarkable progress. While more work is needed to deepen our understanding of the hallmarks and their interactions, scientists have already identified potential genetic, nutritional, and pharmacological longevity interventions, and several human trials are underway. However, the time has come to expand the Hallmarks framework to include social determinants of aging, argues University of Southern California professor and AARP Chair in Gerontology, Eileen Crimmins.
Crimmins explains that the social hallmarks aren’t just a vague reference to social factors influencing aging. Crimmins analysed data from the Health and Retirement Study, a large, nationally representative study of Americans over 56, and showed that social metrics were strong predictors of aging, even when biological factors were accounted for. Here is how she explained it in a press release:
Variability in human aging is strongly related to the social determinants of aging, and it remains so when extensive biology is introduced as mediating factors. This means that the social variability in the aging process is only partly explained by the biological measures researchers currently use.
Crimmins focused on five social hallmarks: socioeconomic status, adverse childhood experiences, adult trauma, negative psychological states, and poor health behaviors such as smoking and drinking. Her models included these along with demographic factors (age and sex) and biological metrics such as telomere length, epigenetic age, and the difference between biological and chronological age. She built models with different combinations of these factors to predict multimorbidity, disability, cognitive deficiency, and two-year mortality.
In the model that included social and biological factors, she found that social factors contributed much more than biological factors to the variance in all of the outcomes. In other words, social factors explained most of the difference in aging in this study population. This is a striking finding given that most current longevity research focuses on biological causes and interventions. (The paper is open access; readers interested in more details can have a look at her precise findings.)
Bringing it together
Crimmins notes that a full biological understanding of aging would presumably preclude the need to consider its social determinants.
Our hypothesis is that if we could fully capture the basic biological mechanisms of aging, they would even more strongly explain the social variability in the process of aging, as social factors need to ‘get under the skin’ through biology.
A complete biological picture of aging remains beyond the horizon for the moment. In the meantime, incorporating the social hallmarks into longevity research can not only guide us towards undiscovered biological aging processes but also provide actionable interventions to alleviate the social causes of aging. In the conclusion of her paper, Crimmins wrote:
“We have far to go before we are able to include indicators of all of the hallmarks of biological aging into human population studies, but these initial measures are somewhat disappointing. The evidence presented suggests that focus on the social hallmarks of aging will help to achieve the geroscience agenda to slow human aging.”
This paper focuses on the social hallmarks of aging including low lifetime socioeconomic status, adversity in childhood and adulthood, being a member of a minority group, adverse health behaviors, and adverse psychological states. The “Social Hallmarks of Aging” are analogous to the “Geroscience Hallmarks of Aging” in reflecting a set of underlying and interrelated social causes of multiple age-related health outcomes. The paper presents empirical work incorporating the social hallmarks of aging with indicators of multiple biological hallmarks of aging as well as downstream biology in explaining a range of health outcomes. Results show the relative strength of the associations of social and biological measures with important health outcomes. Social factors are strongly related to physical and cognitive functioning and multimorbidity in this older population; this remains true when the significant number of biological measures are controlled. These results can be interpreted to mean that a significant amount of the social variance in age-related health outcomes is not explained by these measures of biology. Indicators of the geroscience hallmarks of aging only relate modestly to the variability in human health outcomes. Attention to the social hallmarks related to human aging can usefully be incorporated into work on the biological hallmarks of aging to make greater progress in understanding human aging.
Adding the social hallmarks to our longevity toolkit is an excellent idea. It broadens our framework for understanding how humans age and also highlights things that we can do now to address it. While we wait for – and work towards – interventions that could increase our maximum lifespan, there are many choices we can make now to increase median lifespan and healthspan. Social organizations and structures that alleviate the pressures identified in the social hallmarks would improve the lives, health, and lifespan of many people. It would also demonstrate the benefit of longevity research in highlighting and addressing these links, which will help convince people of its value and reinforce that the goal is longevity for the many, not the few.
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 Crimmins EM. Social hallmarks of aging: Suggestions for geroscience research. Ageing Research Reviews (2020), doi: 10.1016/j.arr.2020.101136
 López-Otín C, Blasco MA, Partridge L, Serrano M, and Kroemer G. The hallmarks of aging. Cell (2013), doi: 10.1016/j.cell.2013.05.039.
 Franceschi C, Garagnani P, Parini P, Giuliani C, and Santoro A. Inflammaging: a new immune-metabolic viewpoint for age-related diseases. Nat. Rev. Endocrinol. (2018), doi: 10.1038/s41574-018-0059-4.
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