Aging is an unavoidable process. Increased susceptibility and vulnerability to the diseases are the results of the decreased physiological capacity and the reduced ability to respond to environmental stresses. Results of all these effects increase mortality with aging. However, to understand all the causes of aging are limited with the availability of the today's laboratory technique. On the other hand, changes of aging are manifest from the molecular to the organismic level but there is no defined easily measurable biomarker to show this. One of the major problems is lacking of unique theory exist to explain the mechanisms of aging. Theories of aging can be divided into two general categories: stochastic and developmental-genetic. These are not mutual, particularly when considering the free radical/mitochondrial DNA theory of aging. Increasing evidence suggests that cellular senescence and organismic aging are antagonistically pleiotropic manifestations of evolutionary pressures to prevent malignant transformation. In other words, “Aging may be the price we pay to avoid cancer”. So, for today the major aim should be to live in a healthy condition as much as possible for the health workers and the patients.
Keywords : Aging, stochastic, mitochondrial DNA