The hallmarks of ageing

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The organising framework proposed by López-Otín, Blasco, Partridge, Serrano and Kroemer in 2013, which listed nine candidate processes — genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion and altered intercellular communication — each required to manifest with age, to accelerate ageing when experimentally worsened, and to retard it when experimentally improved. The 2023 revision expanded the list to twelve, adding disabled macroautophagy, chronic inflammation and dysbiosis. The framework is the field's common vocabulary and it is worth reading for what it does not claim: it is a set of criteria for candidate mechanisms, not a demonstration that any of them causes ageing in humans, and the authors are explicit that the hallmarks are interconnected in ways that make single-target intervention unlikely to be sufficient.

A node is not a place. Drawing it on a map would assert something about the world that no stored fact supports.