From Anesthesiology News:
“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).”
The problem with this study is that there are changes with any surgery requiring general anesthesia or neuraxial anesthesia. It didn't appear as though they investigated any differences in outcome between the two modes.
Even when we think that neuraxial anesthesia would protect from cognitive decline, it actually isn't that clear that there is any difference.