Amyloid imaging and cognitive decline in nondemented oldest-old: the 90+ Study

Abstract

Background: The goal of this study was to examine cross-sectional and longitudinal associations between cognitive performance and beta amyloid (Aβ) load determined by florbetapir F18 positron emission tomography (PET) in nondemented oldest-old.

Methods: Thirteen nondemented (normal or cognitively impaired nondemented) participants (median age, 94.2 years) from The 90+ Study underwent florbetapir-PET scanning within 3 months of baseline neuropsychological testing. Amyloid load was measured with a semi-automated quantitative analysis of average cortical-to-cerebellar standardized uptake value ratio (SUVr) and a visual interpretation (Aβ- or Aβ+). Neuropsychological testing was repeated every 6 months.

Results: At baseline, SUVr correlated significantly with tests of global cognition and memory. During follow-up (median, 1.5 years), the Aβ+ group had steeper declines on most cognitive tests, particularly global cognitive measures.

Conclusion: This preliminary study suggests that greater amyloid load is associated with poorer cognition and faster cognitive decline in nondemented oldest-old. Amyloid load may identify individuals at increased risk of developing Alzheimer's disease.

Figure 1. Scatter plot of neuropsychological test scores at baseline versus average cortical SUVr in non-demented participants from The 90+ Study

3MS = modified Mini-Mental State Exam; MMSE = Mini-Mental State Exam; CVLT = California Verbal Learning Test; BNT = Boston Naming Test; CIND = cognitive impairment no dementia; corr = Pearson correlation; SUVr = standardized uptake value ratio Scatter plots show people with baseline cognitive diagnosis of ‘normal’ (closed circles) and ‘cognitive impairment no dementia’ (open squares).

Figure 2. Longitudinal trajectories of neuropsychological tests in Aβ- and Aβ+ non-demented participants from The 90+ Study

Abbreviations: Aβ- = low amyloid load according to median visual score (0,1) ; Aβ+ = high amyloid load according to median visual score (2,3,4); 3MS = modified Mini-Mental State Exam; MMSE = Mini-Mental State Exam; CVLT = California Verbal Learning Test; BNT = Boston Naming Test. Trajectories are for people with baseline cognitive diagnosis of ‘normal’ (closed circles) and ‘cognitive impairment no dementia’ (open squares). Slopes indicate the average yearly rate of change in cognitive tests (solid thick lines).