It might not just be old age causing forgetfulness. A new study, published in the journal Anaesthesia, found associations with decreased cognitive function and time under general anesthesia or neuraxial blockade.
This observational study followed nearly a thousand middle-aged patients at the Wisconsin Registry for Alzheimer’s Prevention, testing the memory and executive function of participants on two separate occasions, nine years apart, wherein more than 300 had surgery before the second test. Testing several different measures of memory, the authors generally found surgeries with anesthesia were associated with declined cognition. But, they said the changes were overall small and not very noticeable to the patients themselves. They also recognized the challenge of connecting anesthesia and memory, though they were confident in their patient groups and study methods.
“There’s no way to sort out the relative contributions of surgery and anesthesia to our observations with the data we have and can get,” said Kirk Hogan, MD, JD, senior author of the study and a professor in the anesthesiology department at the University of Wisconsin-Madison School of Medicine and Public Health. “No one in our population sample has had anesthesia in the absence of a qualifying surgery, or a qualifying surgery in the absence of anesthesia.”
Using a 30-point diagnostic test, they found patients who had undergone surgery went down one point on average over the timespan (P=0.013). Out of 670 participants who had normal first tests, 77 declined to abnormal in the second test, 18% of surgery patients (21 of 114) and 10% of non-surgery patients (56 of 556). The researchers also found associations between reduced immediate memory and number of past surgeries (beta coefficient (SE) 0.08 (0.03), P= 0.012), as well as longer cumulative surgeries and working memory decline (beta coefficient (SE) -0.01 (0.00), P=0.028).
While this work begins to build on earlier research, specifically similar studies including anesthesia and the elderly, the researchers note that this is only the beginning. “It’s a pressing question but will require other study designs to tease it apart,” Hogan said.