Organ/body weight loss with aging: evidence for co-ordinated involution.

Loss of body weight, during later stages of aging, is a phenomenon recognized in all human populations studied. Reduction of body weight is accompanied by a loss of internal organ weight and volume. The usual approach is to describe organ weight versus age. However, organ weight can be related to overall body weight, by means of the allometric equation. This general expression can be used to relate the weight of each of several organs to that of the body, and offered a good description of data for a reported Japanese autopsy study on males and females over the age of 60 years. The equations were also used in describing the ratio of organ weights (such as the spleen/liver weight). A further extension was in examining the terms of the allometric equation (a constant and an exponent for each organ), and noting a close coupling between male and female values. The allometric description of organ weights versus body weight, suggests a 'co-ordinated involution', and appears worthy of further investigation.