Cognitive changes following major surgery not linked with changes in Alzheimer's-related biomarkers

Cognitive changes following non-neurologic and non-cardiac surgery were not associated with changes in Alzheimer's disease-related biomarkers in older patients, according to a study led by a team at Duke University School of Medicine.

The finding, published online in the journal Annals of Clinical & Translational Neurology, could help ease concerns that Alzheimer's disease risk might be increased by major surgeries and/or general anesthesia.

There has been evidence from other studies of cognitive decline following anesthesia and surgery, and laboratory studies have found that anesthetic drugs and surgical stress accelerate underlying pathways of Alzheimer's disease."

Miles Berger, M.D., lead author, associate professor, Duke's Department of Anesthesiology

"However, in over 100 patients undergoing a wide variety of major surgery types under general anesthesia, we found no correlation between post-operative changes in thinking/memory and in Alzheimer's disease-related biomarkers in the fluid surrounding the brain and spine," Berger said.

The Duke researchers analyzed data from a study they recently completed in older patients undergoing a variety of surgical procedures scheduled to last at least two hours under general anesthesia, with at least a one-night hospital stay. These surgeries included procedures commonly performed in older adults, ranging from hip, knee and shoulder replacements to surgeries performed for a number of different cancers.

The researchers measured cognition and obtained cerebrospinal fluid before surgery and six weeks after surgery, in over 100 patients age 60 and above. Spinal fluid was analyzed for proteins that are involved in Alzheimer's disease, including amyloid beta, tau and the phosphorylated version of tau.

They found no significant changes among the study participants between the two testing periods, although there were postoperative declines in verbal memory and improvements in executive function.

"This should be a reassuring message to anesthesiologists, surgeons, older surgical patients and their family members," Berger said. "These data suggest that anesthesia and surgery are unlikely to accelerate the underlying processes involved in Alzheimer's disease in older adults, at least at the level of spinal fluid markers that have been closely associated with the development of Alzheimer's disease. Further, while some patients do experience thinking and memory problems within weeks to months after surgery, our data suggest that these problems do not reflect an acceleration of several key processes that lead to Alzheimer's disease."