Subtle postoperative cognitive disorder in preclinical Alzheimer's disease

We examined the association between preclinical Alzheimer's disease (AD) and undergoing anesthesia and surgery ("surgery" henceforth) in a cohort of elderly individuals with a subjective cognitive decline (SCD).

Individuals with SCD (N = 268) were enrolled in a longitudinal follow-up study. Participants underwent comprehensive yearly cognitive evaluation for a period of 4 years. Brain amyloid load and glucose metabolism were studied by 18F-Florbetapir and Fluorodeoxyglucose positron emission tomography (PET) at baseline and after two years of follow-up. Exposure to surgery was systematically assessed during the first two years of follow-up. The association between surgery, cognition and AD markers was evaluated using generalized linear mixed models for cognition and linear models for neuroimaging markers.

Sixty-five participants (24.25%) underwent surgery during the first year of follow-up, and 43 (16.04%) during the second year. Undergoing surgery had no overall impact on cognition over 4 years of follow-up nor on amyloid load and brain metabolism at two years of follow-up. However, a second step analysis revealed a small but significant association between undergoing surgery and a subtle decline in executive functions such as mental flexibility and divided attention (TMT B-A), in participants with greater amyloid load at baseline (Cohen's f2 = 0.01, multiple comparison corrected p < 0.001). Highly educated participants with surgery had significantly decreased metabolism over two years, when compared to low educated participants (Cohen's f2 = 0.04, p = 0.031).

Our results suggest that surgery is associated with an increased risk of subtle cognitive decline after surgery, in the cognitively healthy elderly at risk for AD.