Abstract: Background:Major surgery has been associated with perioperative neurocognitive disorders (PND), but the contributing factors and long-term prognosis are uncertain. We hypothesize that preclinical Alzheimer?s disease (AD) might predispose to cognitive deterioration after surgery. Objective:To analyze the effect of amyloid-? on the cognitive trajectory after orthopedic surgery in a sample of non-demented subjects. Methods:Non-demented individuals older than 65 years that were on the waiting list for orthopedic surgery with spinal anesthesia underwent a neuropsychological assessment before and after surgery. During surgery, cerebrospinal fluid samples were obtained to determine AD biomarkers. Results:Cumulative incidence of PND was 55.2%during a mean follow-up of nine months. The most affected cognitive domains were executive function and constructional praxis. The presence of abnormal levels of amyloid-? was associated to a postoperative impairment in verbal and visual memory tests. According to their AD biomarker profile, participants were categorized as either Amyloid Positive (A+) or Amyloid Negative (A-). The incidence of PND did not differ between both groups. The A- group showed a tendency similar to the global sample, worsening in executive function tests and improving on memory scales due to practice effects. In contrast, the A?+?group showed a notable worsening on memory performance. Conclusion:Our findings support the hypothesis that surgery may promote or accelerate memory decline in cognitively asymptomatic subjects with brain amyloid-? deposits.

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