Four studies could be included in the meta-analysis of IL-6; the results showed a significant increase in this biomarker in serum (OR = 1.88, 95% CI 1.01 to 1.637) in patients who developed delirium, with high heterogeneity (τ2 = 0.31, I2 = 76.75%). The gene discussed is IL6; the disease is delirium.