• Department of Radiology, Wake Forest School of Medicine, Winston-Salem, North Carolina.
• Department of Biostatistics and Data Science, Division of Public Health Sciences, Wake Forest School of Medicine, Winston-Salem, North Carolina.
• Department of Radiology, Stanford University Medical Center, California.
• Department of Internal Medicine, Section on Gerontology and Geriatric Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina.
• California Pacific Medical Center Research Institute, San Francisco.
• Department of Biomedical Engineering, Wake Forest School of Medicine, Winston-Salem, North Carolina.

BACKGROUND: Muscle metrics derived from CT are associated with adverse health events in older persons, but obtaining these metrics using current methods is not practical for large datasets. We developed a fully-automated method for muscle measurement on CT images. This study aimed to determine the relationship between muscle measurements on CT with survival in a large multicenter trial of older adults.

METHODS: The relationship between baseline paraspinous skeletal muscle area (SMA) and skeletal muscle density (SMD) and survival over 6 years was determined in 6803 men and 4558 women (baseline age: 60-69 years) in the National Lung Screening Trial (NLST). The automated machine learning pipeline selected appropriate CT series, chose a single image at T12, and segmented left paraspinous muscle, recording cross-sectional area and density. Associations between SMA and SMD with all-cause mortality were determined using sex-stratified Cox proportional hazards models, adjusted for age, race, height, weight, pack-years of smoking, and presence of diabetes, chronic lung disease, cardiovascular disease, and cancer at enrollment.

RESULTS: After a mean 6.44 ± 1.06 years of follow-up, 635 (9.33%) men and 265 (5.81%) women died. In men, higher SMA and SMD were associated with a lower risk of all-cause mortality, in fully adjusted models. A one-unit standard deviation increase was associated with a hazard ratio (HR)=0.85 (95%CI=0.79,0.91;p<0.001) for SMA and HR=0.91 (95%CI=0.84,0.98;p=0.012) for SMD. In women, the associations did not reach significance.

CONCLUSION: Higher paraspinous SMA and SMD, automatically derived from CT exams, were associated with better survival in a large multicenter cohort of community-dwelling older men.