What aging is? Its definition and concept.

ag·ing (jng)
n.
1. The process of growing old or maturing.
2. An artificial process for imparting the characteristics and properties of age.

Ageing, the process of growing old, is defined as the gradual biological impairment of normal function, probably as a result of changes made to cells (mitotic cells, such as fibroblasts and post-mitotic cells, such as neurons) and structural components (such as bone and muscle). These changes would consequently have a direct impact on the functional ability of organs (such as the heart, kidney and lungs), biological systems (such as the nervous, digestive and reproductive system) and ultimately the organism as a whole.

The following is a description setting out five criteria’s for ageing, as proposed by Strehler (1962).

Cumulative: Effects of ageing increase with time.

Universal: All members of a species display signs of ageing.

Progressive: Ageing is a series of gradual changes.

Intrinsic: Changes would take place even in a “perfect” environment.

Deleterious: Changes which occur compromise normal biological functions.

Like ageing, disease is also defined as an impairment of normal function within a living organism. Since the ageing process leads to biological impairment, it would not therefore be a surprise if some of these age-associated changes manifest themselves as disease. Evidence providing a link between ageing mechanisms and age-related disease development/progression is gradually increasing

Aging: The process of becoming older, a process that is genetically determined and environmentally modulated.

Research into aging: To sum up the state of research into aging is well beyond the confines of this space (and this writer's talents). However, here is one type of research into the genetics of aging.

A gene has been discovered that helps determine the life-span of the fruit fly Drosophila. When the gene is mutated (altered), it can extend the life-span of fruit flies. It doubles their life-span. The gene has been named Indy (for I'm not dead yet). It appears that the protein encoded by this gene transports and recycles metabolic byproducts.

Defects in the gene may lead to production of a protein that renders metabolism less efficient so that its body functions as if the fruit fly were dieting, even though its eating habits are unchanged. Mutations in Indy thus appear to create a metabolic state that mimics caloric restriction, which has been shown to extend life-span

Defining old

"The ageing process is of course a biological reality which has its own dynamic, largely beyond human control. However, it is also subject to the constructions by which each society makes sense of old age. In the developed world, chronological time plays a paramount role. The age of 60 or 65, roughly equivalent to retirement ages in most developed countries, is said to be the beginning of old age. In many parts of the developing world, chronological time has little or no importance in the meaning of old age.

Other socially constructed meanings of age are more significant such as the roles assigned to older people; in some cases it is the loss of roles accompanying physical decline which is significant in defining old age. Thus, in contrast to the chronological milestones which mark life stages in the developed world, old age in many developing countries is seen to begin at the point when active contribution is no longer possible." (Gorman, 2000)

Age classification varied between countries and over time, reflecting in many instances the social class differences or functional ability related to the workforce, but more often than not was a reflection of the current political and economic situation. Many times the definition is linked to the retirement age, which in some instances, was lower for women than men. This transition in livelihood became the basis for the definition of old age which occurred between the ages of 45 and 55 years for women and between the ages of 55 and 75 years for men. (Thane, 1978).

The MDS Project collaborators agreed at the 2000 Harare MDS Workshop to use the chronological age of 60 years as a guide for the working definition of "old"; however, this definition was revisited during this meeting. Many felt this definition was not taking into account the real situation of older persons in developing countries, specifically in sub-Saharan Africa.

Hence, upon further deliberation and discussion during the 2001 Dar es Salaam MDS Meeting, the working definition of "older" or "old" for the purposes of this project was changed to the age of 50 years. It is acknowledged that this is also somewhat arbitrary and introduces additional problems of data comparability across nations, but it is believed to be a better representation of the realistic working definition in Africa.

A brief summary, mainly to reflect the implications for ageing policy, of the reasons behind the decision to use this definition follows. A full description is beyond the scope of this report, but will instead be presented in a forthcoming publication.