In defense of the concept of biological aging measurement--current status

Biological age is the objective assessment of a person's health status. Theoretically, a 'normal' person's biological age--in terms of appearance, performance, and functional capacity--should be the same as his chronological age. Many scientists have attempted to develop systems to accurately determine individuals' biological age. Typically, the approach is to select a battery of test parameters comprised of tests which correlate closely with chronological age. This approach assumes that those traits which vary most closely with age are the best indicators of the aging process. The goal has been to compare an individual to his chronological age peers to determine his relative aging status. Two papers (Costa and McCrae, 1980 and 1985) that criticize this concept and approach have heretofore gone unanswered. Lack of published dissent has caused many gerontologists to assume that Costa and McCrae are correct in their assertions that biological age cannot be measured and is not a valid concept. Consequently, some scientists have been reluctant to pursue research in this area. The purposes of this paper are: to critically evaluate the questions raised by Costa and McCrae; to reaffirm the validity of the concept of biological age; and to urge continued research in this most important subject.