Based on prior studies, we expect a

Based on prior studies, we expect a completion rate more than 75% and a POCD incidence of approximately 40% at 6 weeks after surgery. With α = 0.05, a 150-patient study will provide more than 90% power in a 2-sided t test to detect a larger increase (Cohen’s d = 1.07) in the CSF monocyte-tolymphocyte ratio from before to 24 hours after surgery in patients who later develop POCD at 6 weeks after surgery.Enrollment of 200 patients will ensure that at least 150 patients complete the 6-week visit (Table 1). Based on preliminary data demonstrating an approximately 50% incidence of postoperative CSF MCP-1 increases, and α = 0.05, a 150-patient study will also provide more than 90% power to detect worse postoperative cognitive function (Cohen’s d = 0.5), as measured by the CCI change from before to 6 weeks after surgery in patients with increased postoperative CSF MCP-1 levels. After univariate t tests, we will perform multivariate linear and logistic regression analyses of continuous and dichotomous cognitive outcomes,respectively, to account for dependencies between MCP-1 and monocytes,adjust for potential confounders that may contribute to POCD, delirium, and/or dementia,2–4,8 and predict outcomes in future patients.