26. What is systems aging?

Systems aging embraces non-reductionist thinking and treats the organism as a coupled, multiscale dynamical system: aging is expressed not only as changes within a certain system, but also as altered interactions among organs (circulating factors, immune tone, neural and metabolic control), modalities, and functional components that can propagate dysfunction or enable compensation. It emphasizes system-level variables that integrate many mechanisms -deleteriome/biological age (state), resilience (recovery kinetics after perturbations), and frailty/deficit accumulation (vulnerability).