Trunk Skeletal Muscle Mass and Phase Angle Measured by Bioelectrical Impedance Analysis are Associated with the Chance of Femoral Neck Fracture in Very Elderly People

Background: The study aimed to investigate the potential association of trunk skeletal muscle mass (tSM) and phase angle measured by bioelectrical impedance analysis (BIA) with the chance of femoral neck fractures in very elderly people. Patients and Methods: This case-control study enrolled 78 femoral neck fracture patients aged over 75 years (29 males) and 1:2 matched healthy controls. All participants were subjected to BIA examination by specialists. tSM, the corrected values by height squared of tSM (tSMI) and phase angle were compared between fracture patients and controls. Multivariate logistic regression was performed to explore the strength of association of femoral neck fracture with tSM, tSMI, and phase angle. Results: tSM (kg) of fracture patients was significantly lower than those of controls in all participants (women: 13.49 +/- 0.42 vs 15.44 +/- 0.39, p<0.05; men: 15.30 +/- 0.71 vs 17.54 +/- 0.78, p<0.05). In the sarcopenic subgroup, fracture patients also got a lower tSM than controls (women: 12.58 +/- 0.21 vs 13.62 +/- 0.16, p<0.05; men:14.41 +/- 0.29 vs 16.07 +/- 0.21, p<0.05). The comparison of tSMI between the two groups was similar to that of tSM. Phase angle (degrees) at 50 kHz in fracture patients was significantly lower than that of controls in women and men (women: 3.70 +/- 0.32 vs 4.61 +/- 0.21, p<0.05; men: 3.50 +/- 0.20 vs 3.84 +/- 0.22, p<0.05). Multivariate logistic regression analysis demonstrated higher fracture chance with significantly associated decreased tSM [women: OR (95% CI): 0.78(0.67-0.91); men: 0.74(0.64-0.86)] and tSMI [women: OR (95% CI): 0.72(0.61-0.85); men: 0.69 (0.59-0.81)]. In addition, per 1 degrees increase of phase angle in the trunk could decrease the fracture risk by 14% for women [OR (95% CI): 0.86 0.79-0.94)] and 29% for men [OR (95% CI): 0.71 (0.64-0.79)]. Conclusion: This study indicates a decrease in tSM, tSMI, and phase angle measured by BIA is significantly related to the increased chance of femoral neck fracture in people aged over 75 years. Strengthening the mass and strength of trunk skeletal muscles may help reduce the risk of femoral neck fracture in elderly patients.