Decline in cognitive function after surgery occurs most commonly in older patients and patients undergoing major surgeries, such as heart surgery. Postoperative Cognitive Dysfunction (POCD) may last a prolonged period of time while Postoperative Delirium (POD) is a more acute disturbance in attention, awareness and cognition. The cause of POCD and POD are not fully understood, however some of the pathophysiology of POCD is similar to that of Alzheimer's disease (AD). Insulin given intravenously during heart surgery has been shown to preserve short and long-term memory function after the operation. Clinical trials further demonstrated that insulin given via the nose (intranasal) improves memory performance of patients with AD or cognitive impairment suggests that intranasal insulin also could be a therapeutic option for POCD and POD. This study is designed to examine the effect intranasal insulin on POCD and POD. The goal is to investigate whether administration of intranasal insulin during and after heart surgery improves cognitive function postoperatively. Participants of the study will be randomly assigned to one of two groups (Group 1: intranasal placebo or Group 2: 40 units of intranasal insulin). Intranasal placebo or insulin will be given just before the surgery and every day after surgery up to day 7. Cognitive function will be assessed using standard neuropsychological tests before surgery and during follow visits three and twelve months after surgery.