INFLUENCE OF WEIGHT AND SEASONAL-CHANGES ON RADIOGRAMMETRY AND BONE DENSITOMETRY

We studied the behavior of radiogrammetric and densitometric measureme nts in relation to season and body weight in a group of 30 healthy pre menopausal women. Measurements were made at 6-month intervals, in summ er/fall when bone density increases and in winter/spring when bone den sity declines. Total body bone mineral content (TBBMC) and regional bo ne mineral content (RBMC) were measured using dual-energy X-ray absorp tiometry (DXA). Metacarpal radiogrammetry was carried out with compute d radiography. Weight and body mass index increased significantly in w inter (P < 0.05) and total body and RBMC decreased (P < 0.001). The op posite occurred in summer: weight and body mass index decreased signif icantly (P < 0.05) and total body and regional bone mineral content in creased (P < 0.001). Differences in TBBMC persisted when the measureme nt was corrected for weight (TBBMC/W) (P < 0.001), but not for metacar pal cortical thickness corrected for weight. In the first measurement made there were significant relations between weight and both TBBMC (P < 0.001) and metacarpal cortical thickness (P < 0.005). The relation between weight and TBBMC remained significant in later measurements, b ut the relation between weight and metacarpal cortical thickness cease d to be significant in the second and fourth measurements. Our results show that there is an important seasonal variation in bone mass and t hat DXA is more sensitive than radiogrammetry in registering these cha nges.