Alzheimer Disease May Be Predicted by Brain Amyloid Levels

Higher amyloid levels in the brains of cognitively normal individuals are associated with later cognitive decline related to Alzheimer disease (AD), a recent study showed.

As part of the Alzheimer Disease Neuroimaging Initiative (ADNI), the study evaluated longitudinal cognitive and biomarker data from 445 cognitively normal individuals in the United States and Canada. The researchers observed participants for a median 3.1 years between August 23, 2005, and June 7, 2016.
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At baseline, participants were assessed via positron emission tomography amyloid imaging or a cerebrospinal fluid assay of amyloid β and classified as having normal or elevated amyloid levels in the brain.

Participants’ mean age was 74 years old, mean education level was 16.4 years, and 52% of participants are female.

Preclinical Alzheimer Cognitive Composite (PACC), Mini-Mental State Examination (MMSE), Clinical Dementia Rating Sum of Boxes (CDR- Sum of Boxes), and Logical Memory Delayed Recall scores were all used to evaluate outcomes related to normal or elevated amyloid.

A total of 243 participants had normal amyloid, and 202 had elevated amyloid. After 4 years, participants with elevated amyloid had worse mean scores on the PACC, MMSE, and CDR-Sum of Boxes compared with participants with normal amyloid. For Logical Memory Delayed Recall after 4 years, between-group scores were not statistically, according to the researchers.

“Exploratory analyses of a cognitively normal cohort followed up for a median of 3.1 years suggest that elevation in baseline brain amyloid level, compared with normal brain amyloid level, was associated with higher likelihood of cognitive decline, although the findings are of uncertain clinical significance,” the researchers concluded. “Further research is needed to assess the clinical importance of these differences and measure longer-term associations.”

—Christina Vogt

Reference:

Donohue MC, Sperling RA, Petersen R, Sun C-K, Weiner MW, Aisen PS; Alzheimer’s Disease Neuroimaging Initiative. Association between elevated brain amyloid and subsequent cognitive decline among cognitively normal persons. JAMA. 2017;317(22):2305-2316. doi:10.1001/jama.2017.6669.