A subgroup analysis that included exclusively post-surgical patients showed no heterogeneity between the studies and a mean difference in serum concentration of S100β at hospital admission between patients who developed delirium and those who did not was 0.04 ng/ml, a p-value of 0.76 for chi-square, I2 of 0%, and a p-value of < 0.00001 for the total overall effect (Supplementary Figure S3) (36, 59, 61). Here, S100B is linked to delirium.