There is limited information on organ-tissue level body composition in elderly people. Among the several organ-tissues, we focused on bone measured using dual energy x-ray absorptiometry (DXA).

The purpose of this study was to investigate the relationship between the site-matched bone mineral density (BMD) and lean soft tissue mass (LSTM), which mostly consists of skeletal muscle mass and comprises an index of physical activity in the arms and legs with a large sample of male Japanese middle-aged and older subjects.

Three hundred and eighty-six Japanese middle-aged and older men participated in this study (ages, 40s: n = 127, 50s: n = 133, 60s: n = 93, 70s: n = 33). BMD and LSTM were measured using DXA (Delphi A-QDR, Hologic) for the anatomical regions of the arms and legs.

There was a significant correlation between age and BMD for the arms, but only trend significance was observed for the legs in all subjects. Moreover, significant relationships between BMD and LSTM in the arms and legs were observed using partial regression analysis controlling for age.

These results suggested that the preservation of LSTM might be a key factor for maintaining appendicular BMD in Japanese middle-aged and older men.