Fig. 3

The restricted spline curve for the association between RC, iron status markers and DM. The histogram of the distribution of lgRC, lgSF, and TBI, and the RCS for the associations between lgRC, lgSF, TBI, and DM with four knots. The red line and shadow area represent odds ratios (ORs, solid lines) and 95% confidence intervals (CIs) after multivariable adjustment for age, sex, BMI, residence, occupation, education, smoking, alcohol consumption, eGFR, LDL-C, HDL-C, antidiabetic drug, average energy intake, average carbohydrate intake, average fat intake, and average protein intake based on the RCS models. RC and SF were lg-transformed and the concentration of lgRC and lgSF were -0.45 and 1.9 [OR = 1] as the reference concentration, respectively. While the concentration of TBI was 34 mg/kg [OR = 1] as the reference concentration. Values outside the 97.5th percentile of RC are not included. RC Remnant cholesterol, OR Odds ratio, CI Confidence interval, SF Serum ferritin, TBI Total body iron