Association between triglyceride-glucose index and femoral neck bone mineral density in women with breast cancer: a retrospective cross-sectional study

Breast cancer (BC) survivors face elevated osteoporosis risk. The triglyceride-glucose (TyG) index, a surrogate marker of insulin resistance(IR), correlates with bone mineral density (BMD) in general populations but remains unexamined in BC women. This retrospective cross-sectional study included 848 female BC patients from the Affiliated Hospital of Nanjing University of Chinese Medicine (2021–2023). TyG index was calculated as Ln[fasting triglyceride (mg/dL) × fasting glucose (mg/dL)/2]. Femoral neck (FN) BMD was measured by dual-energy X-ray absorptiometry. Associations were examined using Spearman correlation and hierarchical multivariable linear regression, with subgroup analyses by age and TyG quartiles. The median age was 60.0 years, the median TyG index was 8.78 (IQR: 8.43–9.15), and the median FN BMD was 0.68 g/cm² (IQR: 0.61–0.76). In univariate analysis, the TyG index was not significantly correlated with BMD ( r = -0.045, P = 0.193). However, after comprehensive adjustment for demographic and metabolic covariates, an elevated TyG index showed a modest inverse cross-sectional association with BMD (β = -0.083, 95% CI: -0.034 to -0.001, P = 0.039), a finding that was consistent after excluding outliers (β = -0.082, 95% CI: -0.036 to -0.001, P = 0.036). Subgroup analyses showed consistent inverse trends across age and TyG quartile strata, although formal interaction testing did not support effect modification by age ( P for interaction = 0.732) or TyG quartile groups (all P for interaction > 0.05). In this cross-sectional study, an elevated TyG index was modestly associated with reduced FN BMD in Chinese BC women. Given the cross-sectional design, no causal inference can be drawn from this association. This exploratory finding, with a relatively small effect size, does not support the use of the TyG index as a clinical tool for osteoporosis risk stratification. Further prospective studies are warranted to determine whether this modest association has any clinical utility.