[Biological Age as a Method for Systematic Assessment of Ontogenetic Changes in the State of an Organism].

Aging is a common feature of living and nonliving systems as a disturbance of the structure of the system accumulating with age. The only cause of aging of a living system, which is capable of renewal, is the insufficiency of renewal. The latter manifests itself as two global mechanisms of aging: the genetically determined nonrenewal of a number of structures that can only die with age (stochastic aging) and the regulatory reduction in the rate of self-renewal of living structures. The regulatory reduction in cellular self-renewal (cell growth and division) is most important. At the same chronological age, the degree of aging of the organism in general, as well as individual organs, cells, and systems of the organism, may be different, reflecting the concept of biological age (BA)--an indicator of the level of development, changes, or deterioration of a structure or function of an element of the organism, a functional system, or the organism as a whole. It is expressed in units oftime by relating the values of biomarkers defining the processes of aging with the standard average statistical dependences of changes in these biomarkers with the chronological age. The concept of BA is directly related to the concept of viability of the organism, which is determined by the sum (integral) of viabilities of its parts (in practice, the residual functional resource). For quantitative characterization of aging in general, the index of integrated biological age is used. To give a detailed characterization, the partial biological ages are used, which reflect the aging of different systems of the organism, as well as a number of indices reflecting its functional and psychological possibilities. The contribution of pathological processes to BA is also taken into account. In addition, the amount of retained adaptive reserves in the physical and nervous and mental aspects, the risk factors, and the factors of longevity should be determined. For this purpose, it is necessary to take into account the family history (hereditary factors) and the individual history (acquired factors). The use ofthe BA determination method by doctors in clinical practice stimulates the development of preventive medicine, which is important to improve both the individual health and the quality of life. The BA determination method is also the main tool for testing the effectiveness of tools and methods of geroprophylaxis.