Clinicaltrials.gov identifier: NCT02767713.

Background The pathogenesis of postoperative cognitive decline (POCD) is still poorly understood; however, the inflammatory response to surgical procedures seems likely to be involved. In addition, our recent randomized controlled trial showed that perioperative corticosteroid treatment may ameliorate early POCD after cardiac surgery. To assess the long-term effect of dexamethasone administration on cognitive function, we conducted a 4-year follow-up. Methods The patients were randomized to receive a single intravenous bolus of 0.1 mg kg− 1 dexamethasone or placebo 10 h before elective cardiac surgery. The endpoint in both groups was POCD incidence on the 6th day and four years postoperatively. Results Of the 161 patients analyzed previously, the current follow-up included 116 patients. Compared to the 62 patients in the placebo group, the 54 patients in the dexamethasone group showed a lower incidence of POCD on the 6th day (relative risk (RR), 0.510; 95 % confidence interval (CI), 0.241 to 1.079; p = 0.067, time interval also analyzed previously) and four years (RR, 0.459; 95 % CI, 0.192 to 1.100; p = 0.068) after cardiac surgery. The change in cognitive status between the two postoperative measurements was not significant (p = 0.010) among the patients in the dexamethasone group, in contrast to patients in the placebo group (p = 0.673). Conclusions Although statistical significance was not reached in the current study, the prophylactic administration of dexamethasone seems to be useful to prevent POCD development following cardiac surgery. However, further large multicenter research is needed to confirm these directions. Trial registration ClinicalTrials.gov identifier: NCT02767713 (10/05/2016).