Total body and regional bone mineral density in men: effect of age.

Abstract

Bone density is related to the risk of fracture, with a decrease in bone density resulting in an increased risk of fracture. The aims of this study were to characterize the relationship between bone mineral density (BMD) and age at different skeletal sites in men, and to determine whether the BMD pattern with age reflects the pattern of fracture in men. We studied 178 healthy Caucasian men, ages 20-79 years (approximately 30 per decade) from a general practitioner register. Spinal radiographs were obtained from men over 50 years of age and graded by a radiologist for spinal osteoarthritis by the method of Kellgren. BMD was measured by dual-energy X-ray absorptiometry at the anteroposterior (AP) lumbar spine, femoral neck, Ward's triangle, trochanter, ultradistal forearm and total body (providing estimates for the pelvis, head, arms, legs, trunk, ribs and spine). Severe osteoarthritis (grades 3 and 4) was associated with increased spine BMD, and therefore individuals with severe osteoarthritis were excluded from analysis of the spine. There was a decrease in height of vertebrae L2-4 in men between 20 and 79 years of age (4%), resulting in a decrease in projected area. The change in BMD in standard deviation units (T-score) between 20 and 79 years was calculated: there were significant decreases at the femoral neck (-1.6), Ward's triangle (-2.4), total body (-0.6), and its subregions the pelvis (-1.4), trunk (-0.8), ribs (-0.7) and legs (-0.7). There was no change in BMD with age at the AP lumbar spine, ultradistal forearm, or the total body subregion of the head. Similar results were found after adjusting for height and weight. Thus, there was only a small decrease in total body BMD across life, but a substantial decrease in BMD of the pelvis and proximal femur, sites rich in trabecular bone. These are the same sites associated with substantial increases in fracture incidence in men with aging.