Age-Dependent Association of Hepatic Steatosis with Vertebral Trabecular Attenuation in Asymptomatic Adults

Background/Objectives: Preserving skeletal health before osteoporosis develops has become an important challenge in preventive medicine. In addition to aging, metabolic dysfunction has emerged as a potential contributor to skeletal deterioration. Hepatic steatosis, a manifestation of systemic metabolic dysfunction, has been associated with impaired bone health; however, whether this relationship differs according to age remains unclear, particularly among asymptomatic adults. This study investigated the age-specific association between hepatic steatosis and CT-derived vertebral trabecular attenuation in adults undergoing voluntary health screening. Methods: This cross-sectional study included 553 asymptomatic Japanese adults (median age, 51 years; range, 20–88 years) who underwent non-contrast trunk CT during voluntary health checkups. Hepatic steatosis was assessed using the liver-to-spleen Hounsfield unit (HU) ratio (L/S ratio), with lower values indicating greater hepatic fat accumulation. Vertebral trabecular attenuation was assessed using the mean L1–L3 HU value. Participants were categorized as younger (≤49 years), middle-aged (50–64 years), or older (≥65 years). Multivariable regression analyses adjusted for demographic, clinical, and lifestyle factors were performed overall and by age group. An additional model assessed whether the association between the L/S ratio and vertebral HU values varied with age. Results: In the overall cohort, a lower L/S ratio was independently associated with lower vertebral HU values (β = 0.088, p = 0.018). In age-stratified analyses, this association was most evident in the younger group (β = 0.169, p = 0.010), but was attenuated in the middle-aged (β = 0.073, p = 0.260) and older groups (β = −0.113, p = 0.355). This age-related attenuation was statistically significant (β = −0.112, p = 0.004). Conclusions: Hepatic steatosis was independently associated with lower CT-derived vertebral trabecular attenuation, with the strongest association observed in adults aged ≤49 years. Although unmeasured factors, including menopausal status, may partly explain the observed age-dependent pattern, these findings suggest that hepatic steatosis may be relevant to skeletal health in younger adults and could help identify individuals who may benefit from early assessment and preventive care.