AGE IMPACTS THE RELATIONSHIP OF SOFT TISSUE MASS TO BONE MINERAL DENSITY

Abstract

1084 The relative influence of fat and lean tissue mass (LTM) on bone mineral density (BMD) is controversial. Part of the problem may lie in the use of total body BMD were approximately 12% is head BMD. The purpose of this study was to examine the association between BMD and soft tissue mass while accounting for the possible influence of factors such as head BMD, age, and athletic. A cohort of 1020 females, 274 of whom were collegiate athletes, all had total body BMD measurements on the Lunar DPX (version 3.61), from which values for lean and fat tissue mass were obtained along with total, arm, leg, and head BMD. The subjects ranged in age from 6 to 84 years. As expected, athletes had significantly higher BMD compared to age-matched nonathletes at all sites except for the head. Stepwise multiple regression was used to determine the best predictors of total and regional BMD. When all ages were included in the analysis, total LTM was the best predictor of both total body BMD and trunk + limb BMD (total body BMD not including head) while arm and leg LTM were the best predictors of arm and leg BMD with R ranging from .68 to .75. Exclusion of the athletes from the analyses yielded similar results. However, when only those participants older than 45 were analyzed, total fat mass was the best predictor of BMD for all sites including trunk + limb (R = .43 to .44). In conclusion, lean tissue mass appears to exert the most influence on BMD in younger females. However, in older females, total fat mass is a better predictor of BMD, possibly because of a greater peripheral synthesis of estrogen.