Fig. 4: Mediation analyses of the associations between preoperative SF levels and POD risk through Hb levels.

Mediation analyses in the overall population (A, B) and subgroups (C, D, E, and F). Subgroup analyses were adjusted as in model 2. a = the effects of log10 SF on Hb; b = the effects of Hb on POD risk. ab: the indirect effect; c: the total effect; c’: the direct effect. *p < 0.05, **p < 0.01, ***p < 0.001. SF serum ferritin; Hb hemoglobin; POD postoperative delirium.