Relation of serum melatonin levels to postoperative delirium in older patients undergoing major abdominal surgery

Objective Postoperative delirium (POD) is a perennial and distressing complication in older patients, and it may be caused by various factors. This study aimed to determine whether serum melatonin levels are associated with POD in older patients who undergo major abdominal surgery. Methods We collected serum samples from patients undergoing major abdominal surgery. Melatonin was measured by enzyme-linked immunosorbent assay and delirium was assessed by the Confusion Assessment Method after surgery. We classified the patients into the POD group and non-POD group. Results A total of 120 patients met the inclusion criteria and 104 patients were included in the analysis. Postoperative serum melatonin levels were significantly lower than preoperative levels. Multivariate analyses showed that a longer duration of anesthesia (odds ratio [OR] = 1.29, 95% confidence interval [CI] = 1.02–1.64), advanced age (OR = 3.36, 95% CI = 1.37–8.22), and lower postoperative levels of melatonin (OR = 0.50, 95% CI = 0.25–1.00) were associated with POD. Conclusions Serum melatonin levels significantly decline after surgery and anesthesia. Significantly decreased serum melatonin concentrations postoperatively may be a biomarker for predicting POD in older patients undergoing major abdominal surgery with general anesthesia.