Fig. 2

Dose–response relationship analysis between BMD and kidney stone. Restricted cubic spline plots of the association between BMD and kidney stone. RCS regression was adjusted for age, race, sex, marital status, education level, smoking status, drinking status, hypertension, diabetes Vitamin D, Calcium, Phosphorus and Magnesium. (Model 3). The blue solid line represents ORs, blue shaded region represents 95% CI. The P value indicates the degree of significant difference between the model and the observed data. The smaller the P value, the more significant the difference. The P Nonlinear value reflects whether there is a nonlinear relationship in the data. If the P Nonlinear value is small, it suggests that a nonlinear relationship may exist. Among all participants, FN BMD (femoral neck bone mineral density) has a nonlinear negative correlation with the prevalence of kidney stones (P value ≤ 0.001, P Nonlinear = 0.013), L1 BMD (first lumbar vertebra bone mineral density) has a nonlinear negative correlation with the prevalence of kidney stones (P value ≤ 0.001, P Nonlinear ≤ 0.001), L2 BMD (second lumbar vertebra bone mineral density) has a linear negative correlation with the prevalence of kidney stones (P value = 0.018, P Nonlinear = 0.164), L3 BMD (third lumbar vertebra bone mineral density) has a linear negative correlation with the prevalence of kidney stones (P value = 0.013, P Nonlinear = 0.085), and L4 BMD (fourth lumbar vertebra bone mineral density) has a nonlinear negative correlation with the prevalence of kidney stones (P value = 0.002, P Nonlinear = 0.021). In the male population, FN BMD has a nonlinear negative correlation with the prevalence of kidney stones (P value = 0.004, P Nonlinear = 0.031), L1 BMD has a nonlinear negative correlation (P value ≤ 0.001, P Nonlinear ≤ 0.001), L2 BMD has a linear negative correlation (P value = 0.017, P Nonlinear = 0.075), L3 BMD has a nonlinear negative correlation (P value = 0.002, P Nonlinear = 0.015), and L4 BMD has a nonlinear negative correlation (P value = 0.004, P Nonlinear = 0.011). In the female population, FN BMD has a linear negative correlation with the prevalence of kidney stones (P value = 0.026, P Nonlinear = 0.731), L1 BMD has a nonlinear negative correlation (P value = 0.001, P Nonlinear = 0.003), L2 BMD has a linear negative correlation (P value = 0.063, P Nonlinear = 0.699), L3 BMD has a linear negative correlation (P value = 0.075, P Nonlinear = 0.137), and L4 BMD has a linear negative correlation with the prevalence of kidney stones (P value = 0.017, P Nonlinear = 0.996)