Abdominal body composition measured by quantitative computed tomography and risk of non-spine fractures: the Osteoporotic Fractures in Men (MrOS) study

Abstract

The effect of abdominal adiposity and muscle on fracture is unclear in older men; therefore, we examined the association among 749 men aged 65+. Among various adipose tissues and muscle groups, lower psoas muscle volume and higher fatty infiltration of abdominal muscle contribute to higher fracture risk independent of BMD. The association of abdominal adiposity and muscle composition with incident fracture is unclear, especially in older men. Therefore, we examined the relationship of subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), abdominal intermuscular adipose tissue (IMAT), and muscle volume with incident non-spine fractures among 749 men aged 65 and older. A case-cohort study design was used with a total of 252 fracture cases and 497 non-cases. We measured volumes (in centimeters) of adipose and muscle tissues obtained from quantitative computed tomography scan at the L4-5 intervertebral space. Three groups of muscle and IMAT were evaluated: total abdominal, psoas, and paraspinal. Cox proportional hazards regression with a robust variance estimator was used to estimate the hazard ratio (HR) of non-spine fractures per standard deviation (SD) increase in the abdominal body composition measures. The mean age among men in the random subcohort was 74.2 ± 6.1 years, and the average follow-up time was 5.2 ± 1.1 years. After adjusting for age, race, clinic site, percent body fat, and femoral neck bone mineral density (BMD), no significant relationship was found between incident fractures and SAT or VAT. One SD increase in muscle volume at the psoas, but not paraspinal, was associated with 28 % lower fracture risk (95 % CI = 0.55-0.95). When IMAT models were further adjusted for corresponding muscle volumes, only abdominal IMAT was significantly associated with fracture risk (HR = 1.30 (95 % CI = 1.04-1.63)). Our findings suggest that lower total psoas muscle volume and higher IMAT of the total abdominal muscle contribute to higher fracture risk in older men independent of BMD.