A growing body of evidence has demonstrated the prognostic value of skeletal muscle area and quality measured by computed tomography (CT) as biomarkers of sarcopenia and frailty. However, there exists little data in normal healthy subjects to inform reference values and determine the effects of advancing age and sex on CT muscle parameters.

Abdominal CT images of patients (20–80 years of age) presenting to the emergency department with benign abdominal symptoms and no significant medical comorbidities were retrospectively collected from 2014 to 2017. Psoas and abdominal wall muscle area (PMA, WMA) and density (PMD, WMD) at the level of the L4 vertebrae were measured with the CoreSlicer.com web app. The normal reference range was computed by non-parameteric 2.5th and 97.5th percentiles stratified by sex and restricted by age to the younger subgroup (20–39 years of age).

The cohort consisted of 390 otherwise healthy patients (162 males, 228 females). The lower reference range for PMA was <22.0 cm² in males and <11.1 cm² in females, and for WMA was <112.2 cm² in males and <75.6 cm² in females. There was a graded decline observed in PMA and WMA among older compared to younger adults (especially ≥60 years of age) (P<0.001) and among females compared to males (P<0.001). There was also a graded decline observed in PMD and WMD among older compared to younger adults (P<0.001), irrespective of sex.

This study has defined the normal reference values and age-associated down-trend for CT muscle parameters at L4 in a healthy population using an accessible web-based software, which help contextualize and interpret these imaging biomarkers of sarcopenia in clinical care.