Longitudinal changes in radial bone density in older men

Objective: To examine changes in radial bone density and biochemical status , with particular reference to calcium, over Is months in a group of older men. Subjects: Thirty-six healthy men (aged 66-76 y) were recruited to the study during July and August, 1993. These men were free-living residents of Edmo nton who were recruited through local organizations for the retired and sem i-retired. Data for the younger group of men (age 29-60 y) were taken from a previous study conducted in our laboratory. Design: Using special-purpose computed tomography (gamma CT), trabecular (T BD), cortical (CBD) and integral (IBD) bone densities (gm/cm(3)) were measu red in the ultra-distal radius at 6-month intervals over 18 months. At base line, and at each subsequent study visit, serum was obtained from each subj ect for determinations of calcium, phosphate, 25-hydroxyvitamin D, alkaline phosphatase, and immunoreactive parathyroid hormone. A 24-h urine sample w as also obtained at each study visit for determination of urinary calcium, phosphate and creatinine. Results: In repeated measures analysis of variance of the data for the olde r men serum 25-hydroxyvitamin D was significantly decreased (P<0.001) over time, while TBD was increased (+0.60% per year, P<0.01). Longitudinal rates of change for TBD, CBD and IBD were: - 0.94%, 0.92% and 0.74% per year res pectively when bone density data at baseline for the older men and the hist orical data for younger men were combined. However, separate analyses of th e data for the younger and the older men indicated no significant age-relat ed changes in bone density for men aged 29-60 y, or for men aged 66-76 y. H owever, differences in TBD, CBD and IBD between the younger and older group s of men were significant (P < 0.001). Conclusions: In a group (n = 36) of older men (mean age 71.7 y) studied lon gitudinally over Is months, bone density in the distal radius did not decre ase over time. Mean bone density in this group of men was, however, signifi cantly (P ( 0.001) lower than in a group of younger men (n = 17, mean age 4 6.7 y). Regression analysis using cross-sectional bone density data at base line for the older male group, and historical data for the younger male gro up, indicates that bone loss occurs with increasing age at a rate of about 1% per year averaged over ages 29-76 y. Bone density variables were not cor related with either height or weight, or with any biochemical or hormonal v ariable measured in this study. Sponsor: The work was funded in part by the Dairy Bureau of Canada.