Hallmarks of Aging

In 2013, Carlos López-Otín, Maria Blasco, Linda Partridge, Manuel Serrano, and Guido Kroemer proposed nine "hallmarks of aging": genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient-sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication [1]. In a 2023 update in Cell, the same group expanded the list to twelve, adding disabled macroautophagy (split out from proteostasis), chronic inflammation, and dysbiosis (gut microbiome imbalance) [2].

Each hallmark meets three criteria the authors specified: it appears during normal aging, experimentally worsening it accelerates aging, and experimentally improving it can slow, stop, or partly reverse aging signs in model organisms [2]. The hallmarks are explicitly interconnected; for example, DNA damage (genomic instability) can trigger cellular senescence, and mitochondrial dysfunction can drive both oxidative stress and inflammation.

What the evidence does not show: the hallmarks framework is a conceptual organizing tool built mostly from model-organism data (yeast, worms, flies, mice), not a set of independently validated human clinical targets; the 2023 paper itself is a review and synthesis, not new primary data, and some critics argue the framework has grown too inclusive to be falsifiable as new hallmarks keep being added [3]. No single intervention has been shown to address all twelve hallmarks simultaneously in humans, and a comparative-biology critique of the framework argued that some hallmarks were defined with mammalian aging specifically in mind and generalize poorly to species with very different aging trajectories, limiting the framework's claim to universality [5].

Bryan Johnson's Blueprint protocol is explicitly organized around several hallmarks (nutrient-sensing via time-restricted eating, mitochondrial function via exercise, inflammation via diet and hs-CRP tracking), and his publicly reported 66% lower hs-CRP compared to an average 10-year-old is one n=1 example of a hallmark-adjacent biomarker outcome, not evidence the underlying hallmark biology was reversed [4].

Critics, including researchers who study the framework's utility, have noted that the hallmarks are correlational categories drawn largely from short-lived model organisms, and that translating any single hallmark into an approved human therapy has proven difficult; as of 2026 no drug has been approved by a major regulator specifically for "treating aging" via a hallmark mechanism [3]. Animal data that motivated the framework include findings such as late-life rapamycin extending lifespan in genetically heterogeneous mice even when treatment started at an advanced age, cited as support for mTOR-linked nutrient-sensing as a tractable hallmark target [6].

The plain takeaway: the hallmarks of aging are the field's best current map of aging biology, not a checklist of proven human treatment targets.