The association between relative grip strength index and trunk bone BMD in American adults aged 20-59: A cross sectional study of the NHANES 2011-2014

Some researchs have shown a positive correlation between hand grip strength and bone mineral density(BMD), but they lack comprehensiveness. In this study, we adjusted for body mass index and analyzed the association between relative grip strength index(RGSI) and trunk bone BMD (TBBMD). # Materials and methods Of 19,931 initial participants, 5,764 adults (aged ≥20 years) with complete TBBMD, grip strength, and BMI data were analyzed. Covariates included gender, age, weight, height, BMI, marital status, family income to poverty ratio (FIR), education level, alcohol, activity, total cholesterol, vitamin D, hypertension, diabetes, cancer, smoke, and sleep status. Missing values were imputed, and RGSI was calculated. Statistical analyses included baseline characteristics, regression, and nonlinear modeling. # Results Analysis of Participants (mean age 39.006 ± 11.545 years; 52.186% male) revealed a positive RGSI-TBBMD association. TBBMD increased across RGSI quartiles (Q1:0.864±0.102 vs. Q4:0.941±0.122, P<0.001). Multiple regression confirmed strong associations in unadjusted (β=0.033, 95% CI[0.029, 0.036], P<0.00001), gender and age adjusted (β=0.013, 95% CI[0.009, 0.017], P<0.00001), and fully adjusted models (β=0.035, 95%CI[0.030, 0.041], P<0.00001). The association was stronger in women (β=0.050) than men (β=0.032). Generalized additive models revealed inverted U-shaped relationships in total variable (inflection RGSI=4.935), males (4.999), females (3.088), age≤30 (4.975), and vitamin D Q4 (4.458), with negative associations above inflection points (all P<0.05). Participants >30 had an approximately linear positive associations. # Conclusion An elevated RGSI was significantly associated with higher TBBMD levels. Collectively, this study highlights the importance of RGSI in assessing TBBMD.