Associations of CT Muscle Area and Density With Functional Outcomes and Mortality Across Anatomical Regions in Older...

The automated segmentation of computed tomography (CT) images has made their opportunistic use more feasible, yet, the association of muscle area and density from multiple anatomical regions with functional outcomes and mortality risk in older adults has not been fully explored. We aimed to determine if muscle area and density at the L1 and L3 vertebra and right and left proximal thigh were similarly related to functional outcomes and 10-year mortality risk.

Men from the Osteoporotic Fractures in Men (MrOS) study who had CT images, measures of grip strength, 6 m walking speed, and leg power (Nottingham Power Rig) at the baseline visit were included in the analyses (n = 3290, 73.7 ± 5.8 years). CT images were automatically segmented to derive muscle area and muscle density. Deaths were centrally adjudicated over a 10-year follow-up. Linear regression and proportional hazards were used to model relationships of CT muscle metrics with functional outcomes and mortality, respectively, while adjusting for covariates.

Muscle area and density were positively related to functional outcomes regardless of anatomical region, with the most variance explained in leg power (adjusted R ² = 0.40-0.46), followed by grip strength (adjusted R ² = 0.25-0.29) and walking speed (adjusted R ² = 0.18-0.20). A one-unit SD increase in muscle area and density was associated with a 5%-13% and 8%-21% decrease in the risk of all-cause mortality, respectively, with the strongest associations observed at the right and left thigh.

Automated measures of CT muscle area and density are related to functional outcomes and risk of mortality in older men, regardless of CT anatomical region.