Increased BMD in SLD Patients Without Advanced Hepatic Fibrosis: Evidence From the NHANES 2017-2020 Database

Background: Recently, metabolic dysfunction-associated steatotic liver disease (MASLD) has been proposed to replace the liver condition previously known as nonalcoholic fatty liver disease (NAFLD), thereby redefining the subcategories of steatotic liver disease (SLD). However, the clinical relevance of SLD subcategories and their relationship with bone mass is lacking. In this study, we aimed to explore the potential association between the commonly proposed subclasses of fatty liver disease and bone mass. Methods: A cross-sectional study using the data from the 2017-2020 cycle of the National Health and Nutrition Examination Survey (NHANES), involving 4237 participants aged 18 years and older who underwent vibration-controlled transient elastography (VCTE) and dual-energy X-ray absorptiometry (DXA), was conducted. A weighted generalized linear model was used to analyze the association of the SLD subcategories and bone mass changes including bone mineral content (BMC), bone area, and bone mineral density (BMD) in the femur and spine, with adjustments for potential covariates. Furthermore, a weighted generalized additive model was employed to assess the dose-response relationships between controlled attenuation parameter (CAP), liver stiffness measurement (LSM), and BMD. Results: A total of 2635 and 1602 participants were included for analysis of the femur and lumbar spine, respectively. Compared to healthy individuals, positive correlations were observed between all three SLD subgroups (MASLD, MetALD, and ALD) and BMC, and BMD in the femur and spine, but no association with the bone area was identified. Moreover, CAP exhibited a strong positive correlation with BMD across all femoral and spinal scan sites. It was also positively correlated with BMC in some femoral scan sites and all spinal scan sites but was associated with the bone area only in certain femoral scan sites and not in spinal scan sites. In contrast, LSM showed clear positive correlations with BMD in some femoral and all spinal scan sites, as well as with BMC in certain femoral and spinal scan sites. However, LSM did not correlate with the bone area in any femoral or spinal scan sites. Besides, LSM showed a nonlinear association with these indicators. Subgroup analysis revealed a positive correlation between CAP and BMD only in individuals with CAP > 248 dB/m, BMI ≥ 25 kg/m², and LSM < 11.7 kPa. Additionally, in females and individuals with LSM < 11.7 kPa, LSM was positively correlated with BMD, whereas in those with LSM ≥ 11.7 kPa, LSM showed a negative correlation with BMD. Conclusions: Our findings highlighted a positive association between SLD and BMD; however, the association was likely influenced by liver fibrosis. Studies in large scale cohorts with a longer follow-up are warranted to elucidate the impacts of hepatic steatosis and associated pathologies on bone health.