Dynamics of Stability: The Physiologic Basis of Functional Health and Frailty

TLDR

Healthy physiological systems exhibit irregular, complex dynamics across multiple timescales that enable adaptive responses, but perturbations trigger a transient shift to a less complex reactive tuning mode, and aging or disease reduce this complexity, leading to maladaptive responses. The study aims to use nonlinear mathematical techniques to quantify physiological dynamics for predicting frailty onset and to explore interventions that restore healthy dynamics to prevent functional decline. The authors employ nonlinear mathematical methods to quantify physiological dynamics and assess interventions that restore healthy dynamics. Loss of complexity in physiological dynamics, as seen with aging and disease, leads to maladaptive responses and contributes to functional decline and frailty.

Abstract

Under basal resting conditions most healthy physiologic systems demonstrate highly irregular, complex dynamics that represent interacting regulatory processes operating over multiple time scales. These processes prime the organism for an adaptive response, making it ready and able to react to sudden physiologic stresses. When the organism is perturbed or deviates from a given set of boundary conditions, most physiologic systems evoke closed-loop responses that operate over relatively short periods of time to restore the organism to equilibrium. This transiently alters the dynamics to a less complex, dominant response mode, which is denoted “reactive tuning.” Aging and disease are associated with a loss of complexity in resting dynamics and maladaptive responses to perturbations. These alterations in the dynamics of physiologic systems lead to functional decline and frailty. Nonlinear mathematical techniques that quantify physiologic dynamics may predict the onset of frailty, and interventions aimed toward restoring healthy dynamics may prevent functional decline.