Osteopenia means low bone density. This differs from osteoporosis, a common condition in which the bones are brittle and weak and fracture easily. Osteopenia is not a disease but is a marker for risk of fractures. Older persons are at risk of having unrecognized osteoporosis, which may be discovered only after a fracture (such as a broken hip). Bone densitometry is a simple, painless test that measures bone density. If the bone density is already abnormal, lifestyle changes can help slow progression of bone loss and reduce the occurrence of fractures. The December 6, 2006, issue of JAMA includes an article about osteopenia.