ALB and delirium: Moreover, while risk factors for delirium have been identified (including old age, pre-existing cognitive impairment, extensive surgical procedure, longer operation, higher number of comorbidities, blood transfusion, longer management in an intensive care unit, and decreased serum albumin concentration [3, 5, 6, 20–24]), few studies have examined the factors associated with subsyndromal delirium [13, 25], although Cole et al. have suggested that the risk factors of subsyndromal delirium are similar to those associated with delirium [13].