Frailty as a nexus between the biology of aging, environmental conditions and clinical geriatrics

Chronic diseases often determine pathologic phenotypes similar to those traditionally attributed to aging, such as accelerated decline of muscle mass and increments of basic metabolic rate, suggesting that the true nature of aging is progressively increasing entropy in the face of failing homeostatic mechanisms. Aging in different animal species and in humans suggest that increasing entropy causes major problems in four domains; body composition, energetic imbalance between availability and demand, homeostatic dysregulation, and neurodegeneration. In humans, loss of integrity and function in these domains causes manifestations similar to frailty, especially if the damage is severe and/or involves multiple domains, and has catastrophic consequences, such as physical and cognitive disability. Characterizing these phenotypes, and understanding the mechanisms by which they emerge with increasing entropy is a necessary step to find interventions that can prevent, delay or moderate the effects of aging. Pharmacological and non-pharmacological interventions that may effectively modulate the aging phenotypes are actively studied and will certainly be ready in the near future. Until then, creating a "senior friendly society", that allows maximal independence but also promotes an active and healthy lifestyle may be the most cost-effective intervention to improve the quality of life in the population.