Bone width is correlated positively with the upper to the lower segment ratio in elderly men--the MINOS study

Before puberty, limbs grow more rapidly than the spine. During puberty, lengthening of the spine and increase in bone width accelerate. Correlation of parameters with lengths of the upper and lower segments and with the upper/lower segment ratio may indicate the period of growth critical for their determination. We assessed the association of bone mineral and width with the upper/lower segment ratio in 542 elderly men from the MINOS cohort. Areal bone mineral density (aBMD) was measured at the lumbar spine and right hip using pencil-beam dual-energy X-ray absorptiometry and at the distal forearm using single energy X-ray absorptiometry. Upper/lower segment ratio correlated positively with bone mineral content (BMC), aBMD and width of third lumbar vertebra (L3), femoral neck and distal radius. Men in the highest quartile of the upper/lower segment ratio had larger bones by 2.5 to 5.0% (0.3-0.4 SD, p<0.02-0.002) compared with the lowest quartile. Bone width correlated more strongly with the upper segment length than with that of the lower one. Volumetric BMD (vBMD) did not correlate with the upper/lower segment ratio nor with the lengths of the body segments. At the femoral neck and distal radius, men in the highest quartile of the upper/lower segment ratio had higher estimated cortical thickness (5.3%, 0.41 SD, p<0.01 and 4.0%, 0.31 SD, p<0.03), bigger cortical area (8.0%, 0.54 SD and 6.8%, 0.52 SD, p<0.0001) and higher estimated bending strength (9.3 to 13.3%, 0.46 to 0.54 SD, p<0.0001). Elderly men with the higher upper/lower segment ratio had higher BMC and bending strength because they had wider bones, not higher vBMD. The bone size correlated positively with the length of the upper segment, not negatively with that of the lower segment. Our data may suggest an important role of pubertal growth for both bone width and strength in men but do not establish the determinants of this association. Given methodological limitations, these results need to be confirmed in a younger and more representative group of men.