The Association of Brain-Related Circulating miRNAs and Delirium Among Cardiac Surgery Patients

Background: Delirium is a neuropsychiatric syndrome that is pathophysiologically related to both mental (dementia, depression) and physical illness. Its occurrence results in a poor prognosis. Specific miRNAs play a role in regulating central nervous system development, neuroinflammation, and neurodegeneration. This study investigates whether specific miRNAs (miR-9-3p, miR-34c-5p, miR-96-5p, miR-183-5p, and miR-374-3p) related to brain function are associated with an increased risk of postoperative delirium. Methods: A total of 224 adult individuals scheduled for elective cardiac surgery were eligible to participate in the study. Prior to surgery, each patient underwent psychiatric evaluation to identify major depressive disorder based on the DSM-5 criteria. Delirium diagnosis was established with the use of the Confusion Assessment Method. Following miRNA expression profiling, cDNA synthesis was conducted on 60 delirium patients and 60 randomly selected non-delirium individuals. MiRNA dqPCR analysis was performed on the serum samples obtained one day before and the day after surgery. Results: Of the 177 patients finally included, 34% (61 cases) experienced delirium. Univariate comparisons revealed that preoperative miR-96-5p (p=0.05) and miR-183-5p (p=0.001), along with postoperative miR-34c-5p (p=0.009), miR-96-5p (p=0.07), and miR-183-5p (p=0.05), were associated with the risk of post-surgery delirium. However, after conducting multivariate logistic regression analysis, only miR-183-5p was found to be independently associated with the risk of delirium development. Other predictors of delirium included an ongoing episode of depression, peripheral vascular disease, female gender, active smoking, and increased postoperative pCO2 concentration. Conclusion: The current study revealed that preoperatively decreased expression of miR-183-5p predicts delirium development after cardiac surgery.