5. Mean Lifespan Can be Increased by Targeting Weak Links and Reducing Fluctuations

There are two reasons people die from aging-related causes earlier than the species’ lifespan ceiling. First, aging of organs/systems within the body is not perfectly synchronized. Individuals differ in which organ/systems exhibit elevated biological age. Once a particular organismal system emerges as older compared to other systems, it may remain older, increasing risk of disease in this system and mortality from this disease. Since individuals differ in their organ/system age patterns, they need personalized interventions according to these ageotypes (52, 67, 70), i.e., the strategy may be: diagnose the weakest system, then repair, replace, reprogram, or otherwise reduce the dominant burden there. This approach will increase mean lifespan, squaring the survival curve. Second, even when organismal systems age synchronously, outcomes may diverge because of fluctuations: unpredictable internal variability and external perturbations can increasingly precipitate failures with age. Reducing these fluctuations, by improving robustness, buffering capacity, and recovery dynamics, can also help square the survival curve. In this view, fluctuation and resilience metrics are not competing explanations for aging; they are readouts of how deleteriome burden is buffered and translated into failure. Thus, the most realistic path to shifting mean lifespan toward maximal lifespan is i) personalize care to identify and treat the specific weak links that otherwise set each person’s limiting trajectory, and ii) stabilize the organism to reduce fluctuation-driven failures (increase resilience and recovery).