Postoperative changes in cognition and cerebrospinal fluid neurodegenerative disease biomarkers

OBJECTIVE: Numerous investigators have theorized that postoperative changes in Alzheimer's disease neuropathology may underlie postoperative neurocognitive disorders. Thus, we determined the relationship between postoperative changes in cognition and cerebrospinal (CSF) tau, p‐tau‐181p, or Aβ levels after non‐cardiac, non‐neurologic surgery in older adults. METHODS: Participants underwent cognitive testing before and 6 weeks after surgery, and lumbar punctures before, 24 h after, and 6 weeks after surgery. Cognitive scores were combined via factor analysis into an overall cognitive index. In total, 110 patients returned for 6‐week postoperative testing and were included in the analysis. RESULTS: There was no significant change from before to 24 h or 6 weeks following surgery in CSF tau (median [median absolute deviation] change before to 24 h: 0.00 [4.36] pg/mL, p = 0.853; change before to 6 weeks: −1.21 [3.98] pg/mL, p = 0.827). There were also no significant changes in CSF p‐tau‐181p or Aβ over this period. There was no change in cognitive index (mean [95% CI] 0.040 [−0.018, 0.098], p = 0.175) from before to 6 weeks after surgery, although there were postoperative declines in verbal memory (−0.346 [−0.523, −0.170], p = 0.003) and improvements in executive function (0.394, [0.310, 0.479], p < 0.001). There were no significant correlations between preoperative to 6‐week postoperative changes in cognition and CSF tau, p‐tau‐181p, or Aβ42 changes over this interval (p > 0.05 for each). INTERPRETATION: Neurocognitive changes after non‐cardiac, non‐neurologic surgery in the majority of cognitively healthy, community‐dwelling older adults are unlikely to be related to postoperative changes in AD neuropathology (as assessed by CSF Aβ, tau or p‐tau‐181p levels or the p‐tau‐181p/Aβ or tau/Aβ ratios). Trial Registration: clinicaltrials.gov (NCT01993836).