In vivo assessment of amyloid‐β deposition in nondemented very elderly subjects

Abstract

Objective: This study examined amyloid‐β (Aβ) deposition in 190 nondemented subjects aged ≥82 years to determine the proportion of Aβ‐positive scans and associations with cognition, apolipoprotein E (APOE) status, brain volume, and Ginkgo biloba (Gb) treatment. Methods: Subjects who agreed to participate had a brain magnetic resonance imaging and positron emission tomography scan with 11 C‐labeled Pittsburgh compound B (PiB) following completion of a Gb treatment clinical trial. The youngest subject in this imaging study was 82 years, and the mean age of the subjects was 85.5 years at the time of the scans; 152 (80%) were cognitively normal, and 38 (20%) were diagnosed with mild cognitive impairment (MCI) at the time of the PiB study. Results: A high proportion of the cognitively normal subjects (51%) and MCI subjects (68%) were PiB‐positive. The APOE*4 allele was more prevalent in PiB‐positive than in PiB‐negative subjects (30% vs 6%). Measures of memory, language, and attentional functions were worse in PiB‐positive than in PiB‐negative subjects, when both normal and MCI cases were analyzed together; however, no significant associations were observed within either normal or MCI subject groups alone. There was no relationship between Gb treatment and Aβ deposition as determined by PiB. Interpretation: The data revealed a 55% prevalence of PiB positivity in nondemented subjects age >80 years and 85% PiB positivity in the APOE*4 nondemented elderly subjects. The findings also showed that long‐term exposure to Gb did not affect the prevalence of cerebral Aβ deposition. ANN NEUROL 2013;73:751–761