Geroscience: interweaving complex biological models

Geriatric research and clinical practice encounter challenging issues with the aging of our society. A shifting has occurred from the univocal disease-centered Newtonian models of the past centuries to symptom-centered models (by the clustering of symptoms) in the beginning of the 21th century, and more recently to ageing-centered models (biological clocks). By doing so, we acknowledge that chronological aging is no longer the only driver of aging, and that age has become a dynamic core-player to explain functional declines implicating a myriad of homeostatic systems. Aging has been seen for many decades as a universally present, non-modifiable chronological risk factor for many declines and onset of diseases. Yet, nowadays, aging is seen as a pleiotropic and modifiable complex biological system whose comprehension demands new approaches. In the field of Geroscience, age has shifted from a chronological point of view to a biological dynamic concept, to better understand and study the issues related to longevity. In the present paper, we discuss a conceptual framework on ageing by the “wear and tear” in between the vitality and the allostatic load of an ageing organism. The term vitality, close to the term resilience, was described as the biophysiological status of an individual and the capacity for maintaining homoeostasis in the face of usual daily exposures and of more extreme and unusual or unexpected challenges, such as injury or infection. The allostatic load is the cost of maintaining homeostasis when a system is repeatedly confronted with stressors.