Baseline Muscle Characteristics and Bone Health in Older Adults: CT, MRI, and D3-Creatine Dilution Measures from the Study of Muscle, Mobility, and Aging (SOMMA)

Abstract

The aging population in the United States continues to increase causing concerns associated with fractures, mobility, and morbidity. Many of these health concerns can be associated with the degradations between muscle and bone. Aging disrupts the muscle-bone relationship described by the mechanostat theory, leading to progressive declines in muscle mass, strength, and bone mineral density (BMD), all of which contribute to increased fracture risk. Loss of skeletal muscle during aging impairs mobility and physical performance, while reductions in hip and spine BMD heighten susceptibility to osteoporotic fractures, a major health and economic burden in older adults. Muscle properties and functional measures such as walking speed, chair stand time, and leg strength may play an important role in bone health, yet the interplay between muscle composition, performance, and volumetric BMD (vBMD) remain misunderstood in older populations. Additionally, the utilization of more advanced imaging techniques such as computed tomography compared to dual-energy X-ray absorptiometry provides more advanced metrics for hip and spine volumetric bone mineral densities. This thesis presents results from the following comparisons (1) volumetric bone mineral density to muscle metrics and (2) volumetric bone mineral densities to muscle strength, power, and physical performance. Expanded results in comparison 1 extend to muscle subregion compartments in comparison to compartmentalized vBMD regions. These results provide insights into bone mineral density and its interactions to muscle in older cohorts.