Cerebrospinal Fluid Aβ to Tau Ratio and Postoperative Cognitive Change

Objective: Determination of biomarker and neuropathogenesis of postoperative cognitive change (POCC) or postoperative cognitive dysfunction. Background: POCC is one of the most common postoperative complications in elderly patients. Whether preoperative cerebrospinal fluid (CSF) beta-amyloid protein (A beta) to tau ratio, an Alzheimer disease biomarker, is a biomarker for risk of POCC remains unknown. We therefore set out to assess the association between preoperative CSF A beta 42 or A beta 40 to tau ratio and POCC. Methods: Patients who had total hip/knee replacement were enrolled. The CSF was obtained during the administration of spinal anesthesia. Cognitive tests were performed with these participants at 1 week before and at 1 week and 3 to 6 months after the surgery. Z scores of the changes from preoperative to postoperative on several key domains of the cognitive battery were determined. We then examined the association between preoperative CSF A beta 42/tau or A beta 40/tau ratio and the outcome measures described earlier, adjusting for age and sex. Results: Among the 136 participants (mean age = 71 +/- 5 years; 55% men), preoperative CSF A beta 42/tau ratio was associated with postoperative Hopkins Verbal Learning Test Retention [Z score = 8.351; age, sex-adjusted (adj.) P = 0.003], and the Benton Judgment of Line Orientation (Z score = 1.242; adj. P = 0.007). A beta 40/tau ratio was associated with Brief Visuospatial Memory Test Total Recall (Z score = 1.045; adj. P = 0.044). Conclusions: Preoperative CSF A beta/tau ratio is associated with postoperative changes in specific cognitive domains. The presence of the Alzheimer's disease biomarker, specifically the A beta/tau ratio, may identify patients at higher risk for cognitive changes after surgery.