Osteopenia and osteoporosis result from demineralization of the bones. The concentration of calcified bone in bone tissue is measured as bone mineral density (BMD) and this figure illustrates BMD of the hip. It is normal for bone density to decrease as
In the older population, osteopenia and osteoporosis are more much more common.
Long duration exposure to weightlessness causes the BMD of an individual to move towards the right on this curve. Thus, in a sense, weightlessness produces the same effects on the bones as aging does. In fact, it has been suggested that if humans were s
