Study: Late life is different from aging

December 6th, 2005

Although getting older may seem inevitable, a major new study examines the point in human life at which one's body stops aging.

"For decades, demographers and gerontologists noticed that late life human data did not fit (expected) models: There was a shortage of deaths," say researchers Michael Rose and Casandra Rauser of the University of California-Irvine, and Laurence Mueller of the University of California-Davis. "More specifically, the exponential increase in age-specific death rate seemed to slow down considerably, if not cease."

The sudden plateau in mortality rates after a certain age has long been observed with other organisms, but its presence in human populations has been dismissed as a result of the advent of nursing homes and modern medicine.

"Late life is a unique and distinct phase of life very different from aging," write the authors. "Each phase evolves according to very different rules. Evolutionary biology has a new set of problems to solve."

The authors posit that late life arises after the forces of natural selection affecting both fertility and mortality cease to have an impact.

Their study is detailed in a forthcoming issue of Physiological and Biochemical Zoology.

Copyright 2005 by United Press International