Fracture risk assessment in older adults using a combination of selected quantitative computed tomography bone measures: a subanalysis of the Age, Gene/Environment Susceptibility-Reykjavik Study

Abstract

Bone mineral density (BMD) and geometric bone measures are individually associated with prevalent osteoporotic fractures. Whether an aggregate of these measures would better associate with fractures has not been examined. We examined relationships between self-reported fractures and selected bone measures acquired by quantitative computerized tomography (QCT), a composite bone score, and QCT-acquired dual-energy X-ray absorptiometry-like total femur BMD in 2110 men and 2682 women in the Age, Gene/Environment Susceptibility-Reykjavik Study. The combined bone score was generated by summing gender-specific Z-scores for 4 QCT measures: vertebral trabecular BMD, femur neck cortical thickness, femur neck trabecular BMD, and femur neck minimal cross-sectional area. Except for the latter measure, lower scores for QCT measures, singly and combined, showed positive (p < 0.05) associations with fractures. Results remained the same in stratified models for participants not taking bone-promoting medication. In women on bone-promoting medication, greater femur neck cortical thickness and trabecular BMD were significantly associated with fracture status. However, the association between fracture and combined bone score was not stronger than the associations between fracture and individual measures or total femur BMD. Thus, the selected measures did not all similarly associate with fracture status and did not appear to have an additive effect on fracture status.

Keywords: Bone mineral density; bone strength; elderly; fracture; quantitative computerized tomography.

Fig. 1

Distribution of fracture status by composite bone score category. CBS, composite bone score.

Fig. 2

Associations between fracture status and QCT bone measures (individual and combined) in age-adjusted regression analysis. BMD, bone mineral density; CBS, composite bone score; CI denotes 95% confidence interval; CorTh, femoral neck cortical thickness; FNTB, femoral neck trabecular BMD; M and F represent measures in male and female participants, respectively; MNCS, femoral neck minimal cross-sectional area; QCT, quantitative computerized tomography; TOBD, QCT-derived DXA-like total femur BMD; VBMD, vertebral trabecular BMD. Each bone variable had 2 categories (highest quartile and lowest 3 quartiles); for each bone score variable tested, the reference group was the lowest 3 quartiles. β is the regression coefficient.