Greater D3-creatine muscle mass and MRI thigh muscle volume are associated with higher bone strength in older adults: exploratory findings in The Study of Muscle, Mobility and Aging (SOMMA).

Low BMD and impaired bone strength are established risk factors for fractures in older adults. Decreased muscle size also contributes to fracture risk; however, the relationship between muscle size and bone density, microarchitecture, and strength using state-of-the-art assessment methods is not clear. In The Study of Muscle, Mobility and Aging, muscle size was assessed using whole-body muscle mass (kg, deuterated creatine [D3Cr] dilution method) and thigh muscle volume (L, by MRI). We investigated cross-sectional associations between baseline D3Cr muscle mass and MRI thigh muscle volume with bone volumetric density, microarchitecture, and strength from HR-pQCT at the distal tibia (DT) and radius (DR), and hip areal BMD from DXA at the first annual follow-up visit (year 1). Muscle and bone parameters were standardized within sex and analyses were stratified by sex. Linear regression models were adjusted for age, race, weight, ≥1 alcoholic drink/wk, ever cigarette smoker, total activity from wrist-worn accelerometry, multimorbidity count (0-11), arthritis, and tibia or ulna length. In 181 women (age 76.2 ± 4.7 yr, 86% White) and 118 men (age 76.1 ± 4.3 yr, 93% White), higher thigh muscle volume (per SD: 1.1 L women; 1.5 L men) was associated with higher DT and DR failure load (p < .05). Greater thigh muscle volume was associated with higher DXA total hip BMD in men but not in women. Greater D3Cr muscle mass (per SD: 4.4 kg women; 5.5 kg men) was associated with higher DT and DR failure load (p < .05) in women only. Associations of muscle size with microarchitecture were variable and differed by sex. Given that failure load is a strong predictor of fracture risk, future studies should investigate whether interventions that target muscle size may impact fracture risk in older adults.