The biology of aging

Thanks largely to the power of genetic analysis in model organisms such as Caenorhabditis
elegans (a nematode), Drosophila melanogaster (a fruit fly), and the laboratory mouse, major
advances have been made in the elucidation of what can be termed "public" modulations of
intrinsic biological aging—that is to say, commonalities of gene actions across widely diverse
phyla that explain, in part, the plasticity of processes of aging. There are hints that at least
one such conserved pathway may be operative in our own species. These observations,

together with related research on other biochemical pathways, a long history of research on
the beneficial effects of dietary restriction (most recently including an initial report of its
beneficial effects on healthspan and lifespan in a primate) (Fig. 71-1), and spectacular
advances in genomics raise the possibility that we may one day be able to delay the times of
onset and decrease the rates of progression of aging processes. Such interventions have the
potential to extend the healthspans and, therefore, the functional lifespans of a large
proportion of our population. This new knowledge, however, is still very distant from clinical
translation. Many remain skeptical of the relevance of these experimental findings. Moreover,
we need much more information on the pathophysiology of aging, especially in the
invertebrate models that have provided most of our new knowledge concerning genetic
modulations of lifespan. We will also require more detailed information on the impact of
longevity enhancements upon what can be described as the "terminal decline" of the life
course, the stage of life in humans responsible for protracted morbidity, frailty, and the
consequent loss of the ability to live independently. These terminal declines account for a
very substantial proportion of all health care costs. Finally, the promising new knowledge
needs fuller discussions by ethicists, economists, sociologists, and political scientists, among
others, as to the impacts upon society of any large-scale clinical translations.