Introduction: Longitudinal studies on the age-related bone loss in men concerns the decrease in areal bone mineral density (aBMD), which can be qualified as "apparent bone loss" because it does not reflect the change in bone mineral content (BMC). Loss of BMC can be referred to as "net bone loss" because it does not take into account the morphological basis of the bone loss (decreased periosteal apposition; endosteal bone loss, i.e. bone loss on the trabecular, endocortical and intracortical surfaces). The aim of this study was to assess age-related apparent net and endosteal bone loss as well as their morphological basis and age-related changes during a prospective follow-up in a large cohort of elderly men.
Methods: This analysis was performed in 725 men aged 51-85 at baseline who were followed up for 90 months.
Results: Bone densitometry was carried out at the lumbar spine, hip and whole body by using the HOLOGIC QDR1500 device and at the distal forearm by using the Osteometer DTX100 device. Sixty-five men who abandoned the study after the first examination were older and had lower aBMC at most sites of measurement. Apparent bone loss was significant at the hip, distal forearm and whole body. Net bone loss was also significant at these sites, except for the femoral neck. Periosteal expansion was significant at all sites of measurement. Apparent and net bone loss accelerated with age, whereas the rate of periosteal expansion remained stable. At the distal radius and ulna, endosteal bone loss accelerated with age, whereas the rate of periosteal apposition remained stable.
Conclusion: In a large cohort of elderly men, age-related apparent bone loss (aBMD) at the hip, distal forearm and whole body was determined by the net bone loss (BMC), except for the femoral neck. Apparent and net bone loss accelerated with age, whereas the periosteal expansion rate (bone widening) remained constant. At the distal forearm, age-related acceleration of the apparent bone loss was determined by the higher endosteal bone loss, whereas the periosteal apposition rate (estimated mass of deposited bone) remained constant.