Dual-Energy X-Ray Absorptiometry–Derived Body Composition Asymmetry in Pain-Free Adults

OBJECTIVE: To characterize body composition asymmetry in asymptomatic adults and examine its associations with age, lumbar intervertebral disc degeneration (DD), and physical activity. DESIGN: Dual-energy X-ray absorptiometry scans were performed, and lumbar DD grading, and physical activity levels were assessed in clinically asymptomatic adults in this cross-sectional study. RESULTS: Fifty-one participants were included. Asymmetry in trunk fat and lean tissue mass was present in the overall cohort (P<0.0001), and leg lean tissue mass also differed between sides (P=0.0178), with right-sided predominance in older participants (P=0.0094). Trunk lean AI (TLAI) was higher in older than younger participants (6.3±4.9 vs. 3.5±2.6; P=0.012), whereas the corresponding trunk fat AI (TFAI) difference was not statistically significant (8.0±5.9 vs. 5.0±3.6; P=0.085). Greater age was associated with TLAI (P=0.008), while the trunk fat association was less robust in sensitivity analyses. Signed TFAI and TLAI shifted toward non-dominant-side predominance with greater age (P<0.05). Lumbar DD and physical activity were not significantly associated with asymmetry. CONCLUSION: Body composition asymmetry was most evident in the trunk. Trunk lean asymmetry was greater at older ages, whereas the corresponding trunk fat association was weaker. Because functional outcomes were not assessed, the clinical significance of these findings requires further investigation.