7. Organ-, System-, and Subsystem-Specific Aging

Available molecular and functional evidence suggests that organisms do not age uniformly across tissues, although current measures are projections rather than direct ground-truth measurements of tissue-specific deleteriome accumulation. Organ- and system-specific biomarkers (molecular, functional, event-based, etc.) can define ageotypes and identify weak links—systems whose deleteriome rises faster and that will likely fail first (52, 67). This is the logic behind systems aging: instead of assessing a single clock in the bloodstream, it is better to assess a portfolio of trajectories across organs that together determine resilience and risk. The practical implication is personalized intervention: target the organ system(s) whose aging most strongly determines an individual’s near-term risk. The same concept applies to any subsystem, as aging can be measured for specific functional components, e.g., damage types.