The bone mineral content of weight-bearing bones is influenced by the ratio of sitting to standing height in elderly Gambian women.

Abstract

Body size is an important predictor of bone mineral content (BMC) at various anatomical sites but the influence of relative body proportions on BMC has previously been little studied. Using single- and dual-photon absorptiometry, we measured BMC at the distal and midshaft of the radius, the neck of femur, and the lumbar spine in 190 rural West African women aged 45-84 years. After regression adjustment for age, bone width and weight, sitting height and standing height were not separate significant determinants of BMC, except at the lumbar spine (standing height, p < 0.05). However, the ratio of sitting:standing height was a significant determinant of BMC at the neck of femur and lumbar spine, but not the midshaft or distal radius. The fact that sitting:standing height ratio is a positive predictor for BMC at hip and lumbar spine may reflect a higher peak bone mass or selective conservation of mineral in weight-bearing bones in subjects with a proportionately longer torso. We do not know whether the relationship is racially determined but we recommend that this simple combination of measurements be used in further studies in subjects of all races.