Binary logistic regression analysis identified six independent risk factors for delirium among critically ill patients undergoing cardiac surgery: age (OR 1.030, 95% CI 1.002–1.058, p = 0.038); duration of physical restraint (OR 1.030, 95% CI 1.019–1.040, p < 0.001); IL-6 (OR 1.001, 95% CI 1.00–1.003, p = 0.025); CD19+ B cell count (OR 0.996, 95% CI 0.993–0.999, p = 0.016); CD4+ T cell count (OR 1.005, 95% CI 1.003–1.008, p < 0.001); and CD4/CD8 ratio (OR 5.314, 95% CI 2.796–10.099, p < 0.001) (Table 4). This evidence concerns the gene IL6 and delirium.