A subgroup analysis that included exclusively post-surgical patients still showed high heterogeneity between the studies and a mean difference in serum concentration of IL-6 at hospital admission between patients who developed delirium and those who did not was 29.04 pg/ml, p = 0.0001 for chi-square, I2 of 82%, and p = 0.0002 for the total overall effect (Supplementary Figure S1) (17, 48, 52, 58, 60). The gene discussed is IL6; the disease is delirium.