In adult men, its incidence is roughly equivalent to chronologic age, and it has a strong genetic component.

Growth and development are appropriate for an individual's biologic age (skeletal age) rather than for their chronologic age.

Yet chronologic age so colors the physician's view that the healthy as well as unhealthy older person is often denied medical options that are presented to others.

Additional findings show that the risk of frailty increases with the number of dysregulated physiological systems in a nonlinear pattern, independent of chronic diseases and chronologic age, suggesting synergistic effects of individual abnormalities that on their own may be relatively mild.

Skeletal age, which is estimated from radiographic studies of the left hand and wrist, is usually delayed (typically 2-4 y by late childhood) and is most consistent with the child's height age (age for which a child's height is at the 50th percentile) rather than the child's chronologic age.