Quantitative MRI Biomarker IDs Cognitive Decline Risk

Alzheimer's signature tied to cortical thinning; predicts risk in cognitively normal older adults

WEDNESDAY, Dec. 21 (HealthDay News) -- Cognitively normal (CN) older adults with a low measure of Alzheimer's disease signature (ADsig), a quantitative magnetic resonance imaging (MRI) biomarker, are more likely to develop cognitive decline, according to a study published online Dec. 21 in Neurology.

Bradford C. Dickerson, M.D., from the Massachusetts Alzheimer's Disease Research Center, and David A. Wolk, M.D., from Massachusetts General Hospital -- both in Boston, investigated whether CN individuals with this biomarker are more likely to develop cognitive decline than CN individuals lacking this marker. MRI data from 159 CN individuals from the AD Neuroimaging Initiative Database were processed to derive the ADsig. Participants were classified as ADsig-low (≥1 standard deviation [SD] below the mean: high risk for preclinical AD), ADsig-average (within 1 SD of mean), or ADsig-high (≥1 SD above mean). The change in Clinical Dementia Rating sum of boxes, and selected neuropsychological measures, were used to define the a priori three-year cognitive decline outcome.

The investigators found that 21 percent of individuals with ADsig-low experienced cognitive decline, compared to 7 percent in the ADsig-average group and none in the ADsig-high group (P = 0.03). Logistic regression analysis showed that there was a significant increase (nearly triple) in the risk of cognitive decline with every 1 SD of cortical thinning. Among patients with available baseline cerebrospinal fluid (CSF) data, CSF characteristics consistent with Alzheimer's disease were found in 60, 36, and 19 percent of ADsig-low, ADsig-average, and ADsig-high individuals, respectively (P = 0.1).

"The identification of individuals expressing this quantitative ADsig MRI biomarker may provide investigators with a CN population enriched for AD pathobiology and at relatively high risk for imminent cognitive decline," the authors write.

The authors disclosed financial ties to Pfizer Inc. and GE Healthcare. Data for this study were collected from the Alzheimer Disease Neuroimaging Initiative, which is funded by the pharmaceutical industry.

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