Femoral Neck External Size but not aBMD Predicts Structural and Mass Changes for Women Transitioning Through Menopause

Abstract

The impact of adult bone traits on changes in bone structure and mass during aging is not well understood. Having shown that intracortical remodeling correlates with external size of adult long bones led us to hypothesize that age-related changes in bone traits also depend on external bone size. We analyzed hip dual-energy X-ray absorptiometry images acquired longitudinally over 14 years for 198 midlife women transitioning through menopause. The 14-year change in bone mineral content (BMC, R² = 0.03, p = 0.015) and bone area (R² = 0.13, p = 0.001), but not areal bone mineral density (aBMD, R² = 0.00, p = 0.931) correlated negatively with baseline femoral neck external size, adjusted for body size using the residuals from a linear regression between baseline bone area and height. The dependence of the 14-year changes in BMC and bone area on baseline bone area remained significant after adjusting for race/ethnicity, postmenopausal hormone use, the 14-year change in weight, and baseline aBMD, weight, height, and age. Women were sorted into tertiles using the baseline bone area-height residuals. The 14-year change in BMC (p = 0.009) and bone area (p = 0.001) but not aBMD (p = 0.788) differed across the tertiles. This suggested that women showed similar changes in aBMD for different structural and biological reasons: women with narrow femoral necks showed smaller changes in BMC but greater increases in bone area compared to women with wide femoral necks who showed greater losses in BMC but without large compensatory increases in bone area. This finding is opposite to expectations that periosteal expansion acts to mechanically offset bone loss. Thus, changes in femoral neck structure and mass during menopause vary widely among women and are predicted by baseline external bone size but not aBMD. How these different structural and mass changes affect individual strength-decline trajectories remains to be determined. © 2017 American Society for Bone and Mineral Research.

Keywords: AGING; BONE MODELING; BONE QCT; DXA; MENOPAUSE.

Figure 1

Schematic showing how the inter-individual variation in femoral neck width is associated with coordinated changes in several cortical and trabecular traits that lead to individuals acquiring different sets of bone traits by adulthood and that are predictable by external bone size.

Figure 2

Linear regression analysis showing associations between measures of external bone size (Tt.Ar measured from CT images or bone area measured from DXA images) and a) cortical area, b) relative cortical area, c) cortical tissue mineral density, and d) medullary vBMD.

Figure 2

Linear regression analysis showing associations between measures of external bone size (Tt.Ar measured from CT images or bone area measured from DXA images) and a) cortical area, b) relative cortical area, c) cortical tissue mineral density, and d) medullary vBMD.

Figure 2

Linear regression analysis showing associations between measures of external bone size (Tt.Ar measured from CT images or bone area measured from DXA images) and a) cortical area, b) relative cortical area, c) cortical tissue mineral density, and d) medullary vBMD.

Figure 2

Linear regression analysis showing associations between measures of external bone size (Tt.Ar measured from CT images or bone area measured from DXA images) and a) cortical area, b) relative cortical area, c) cortical tissue mineral density, and d) medullary vBMD.

Figure 3

Linear regression analysis showing associations between aBMD from DXA and a) total area, b) cortical area, c) cortical tissue mineral density, and d) medullary vBMD.

Figure 3

Linear regression analysis showing associations between aBMD from DXA and a) total area, b) cortical area, c) cortical tissue mineral density, and d) medullary vBMD.

Figure 3

Linear regression analysis showing associations between aBMD from DXA and a) total area, b) cortical area, c) cortical tissue mineral density, and d) medullary vBMD.

Figure 3

Linear regression analysis showing associations between aBMD from DXA and a) total area, b) cortical area, c) cortical tissue mineral density, and d) medullary vBMD.

Figure 4

Linear regression analysis showing that bone area measured from DXA increases with body height at baseline.

Figure 5

The 14-year changes in a) aBMD, b) BMC, and c) bone area were compared across tertiles using an ANOVA. Women were sorted into tertiles based on the residuals from a linear regression between bone area and height measured at baseline. The result of posthoc analyses are indicated by the lower case letters; tertiles with different letters indicate p=0.05.

Figure 5

The 14-year changes in a) aBMD, b) BMC, and c) bone area were compared across tertiles using an ANOVA. Women were sorted into tertiles based on the residuals from a linear regression between bone area and height measured at baseline. The result of posthoc analyses are indicated by the lower case letters; tertiles with different letters indicate p=0.05.

Figure 5

The 14-year changes in a) aBMD, b) BMC, and c) bone area were compared across tertiles using an ANOVA. Women were sorted into tertiles based on the residuals from a linear regression between bone area and height measured at baseline. The result of posthoc analyses are indicated by the lower case letters; tertiles with different letters indicate p=0.05.

Figure 6

Schematic depicting the differences in how femoral neck structure and mass change during menopause for women with narrow femoral necks at baseline compared to women with wide femoral necks at baseline.