Subtle postoperative cognitive disorder in preclinical Alzheimer's disease.

BACKGROUND: 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). METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.

Neural correlates of episodic memory in the Memento cohort.

INTRODUCTION: The free and cued selective reminding test is used to identify memory deficits in mild cognitive impairment and demented patients. It allows assessing three processes: encoding, storage, and recollection of verbal episodic memory. METHODS: We investigated the neural correlates of these three memory processes in a large cohort study. The Memento cohort enrolled 2323 outpatients presenting either with subjective cognitive decline or mild cognitive impairment who underwent cognitive, structural MRI and, for a subset, fluorodeoxyglucose-positron emission tomography evaluations. RESULTS: Encoding was associated with a network including parietal and temporal cortices; storage was mainly associated with entorhinal and parahippocampal regions, bilaterally; retrieval was associated with a widespread network encompassing frontal regions. DISCUSSION: The neural correlates of episodic memory processes can be assessed in large and standardized cohorts of patients at risk for Alzheimer's disease. Their relation to pathophysiological markers of Alzheimer's disease remains to be studied.