The effect of melatonin on cognitive functions following coronary artery bypass grafting: A triple-blind randomized-controlled trial

Background: Cognitive dysfunction presents one of the chief causes of postoperative morbidity. Melatonin as a neurohormone can improve neurocognitive functioning and sleep disorders. We evaluated the effect of melatonin on the postoperative cognitive function of patients undergoing coronary artery bypass grafting (CABG).

Materials and methods: A triple-blind randomized-controlled trial was conducted on 66 CABG candidates in Namazee Hospital (Shiraz, Iran). Patients were assigned equally into two groups receiving melatonin 10 mg or a placebo daily for 4 weeks before surgery and 2 days after surgery in the intensive care unit. The Mini-Mental State Examination (MMSE), Tower of London (ToL), and Wechsler Adults Intelligence Scale-Revised (WAIS-R) cognitive function tests were performed in both groups 4 weeks before surgery (time point 1), 2 days after surgery (time point 2), and 6 weeks after initial administration of melatonin (time point 3).

Results: The mean change score (time point 3-time point 1) differed significantly between the two groups in the MMSE (P ≤ 0.001), ToL total score (P = 0.001), and WAIS-R general IQ (P ≤ 0.001), picture completion (P ≤ 0.001), vocabulary (P = 0.024), and digit span (P = 0.01). On the other hand, no significant differences were detected in the WAIS-R block design, ToL total time delay, ToL total lab, and ToL total result scores.

Conclusion: The MMSE and WAIS-R tests revealed that melatonin might have prophylactic effects against postoperative cognitive disturbance in patients undergoing elective CABG.