MMP9 and delirium: After the adjusted duration of education and the intervention group in the models, the mediation effect analysis showed that MMP9 mediated only 1.3% of the association between the Aβ42 ratio and delirium risk (indirect effect: β = −0.001; 95% CI, −0.014–0.005; p = 0.833; direct effect: β = 0.089; 95% CI, 0.045–0.135).