A subgroup analysis that included exclusively post-surgical patients showed moderate heterogeneity between the studies and a mean difference in serum concentration of CRP at hospital admission between patients who developed delirium and those who did not was 11.93 mg/L, with a p-value of 0.03 for chi-square, I2 of 67%, and a p-value of 0.0006 for the total overall effect (Supplementary Figure S2) (20, 46, 47, 49, 55). Here, CRP is linked to delirium.