Defining Aging

Aging can be thought of as the stochastic (random) accumulation of damage to cells of which we are comprised. This ongoing damage is countered by defense and repair mechanisms that vary in efficiency from individual to individual and which tend to fail with age.

It is often said that the best path to a long life is to choose one's parents wisely. There is truth in this as there is about a 30% heritable component to longevity. Attempts to link specific genetic loci to prolonged life remain controversial; however, variation at the FoxO3 locus is associated with longevity in several populations. FoxO proteins are transcription factors involved in the control of a variety of cellular processes likely to be associated with aging including DNA repair, tumor suppression, resistance to oxidative stress, and induction of apoptosis. The aging process is multifactorial (having genetic and environmental components) and involves many genes but aging is associated with a common set of phenotypic and cellular changes; a decreasing ability of organ systems to maintain baseline homeostasis that is magnified by stress. Much of this decline is explained by reduced regenerative ability related to tissue stem cell population loss. Characteristic organ-specific changes are associated with aging. Chronic diseases of the cardiovascular system, joints, and pulmonary system occur in 50%, 35%, and 10% of individuals over age 65, respectively. The manifestations of type 2 diabetes occur in about 15% of this population. The multisystem effects of such chronic diseases and the occurrence of cancer are almost inevitably noted on autopsies of the elderly as either the cause of, or major contributing factors to, death.