HealthDay News — A quantitative magnetic resonance imaging (MRI) biomarker that measures regional cortical thinning has been linked to risk for developing cognitive decline, data indicate.

Cognitively normal (CN) individuals with a low average thickness in nine cortical regions were more likely to show some signs of cognitive decline after three years, Bradford C. Dickerson, MD, from the Massachusetts Alzheimer’s Disease Research Center, and David A. Wolk, MD, from Massachusetts General Hospital, both in Boston, reported online first in Neurology.

They grouped 159 CN individuals from the AD Neuroimaging Initiative Database into three categories based on the imaging biomarker, dubbed the Alzheimer disease signature (ADsig), which previous studies have shown to be a “reliable and valid marker” of mild AD:

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  • 19 participants with cortical thickness values one standard deviation below the mean of the group were classified as ADsig/low, indicating a high risk for cognitive decline.
  • 116 participants with cortical thickness values within a standard deviation of the mean were classified as ADsig/average, indicating an average risk for cognitive decline.
  • 24 participants with cortical thickness values at least one standard deviation above the mean were classified as ADsig/high, indicating a low risk for cognitive decline.

After three years of follow-up, 21% of individuals in the ADsig-low group experienced cognitive decline, compared to 7% in the ADsig-average group and none in the ADsig-high group (P=0.03), the researchers found. Furthermore, the risk for cognitive decline nearly tripled for every standard deviation decrease in cortical thickness, results of a logistic regression analysis revealed (OR = 2.95, 95% CI: 1.2-7.5, P=0.02).

Among patients with available baseline cerebrospinal fluid (CSF) data, CSF characteristics consistent with AD were found in 60% of the ADsig-low group, 36% of the ADsig-average group, and 19% of the ADsig-high group (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 researchers wrote.

They cautioned that the  findings were limited by the study’s relatively small size and short follow-up period and called for larger prospectively designed clinical trials.

In an accompanying editorial, Susan Resnick, PhD, of the National Institute on Aging in Baltimore, and Philip Scheltens, MD, PhD, of VU University Medical Center in Amsterdam, praised the study.

“The ability to identify people who are not showing memory problems and other symptoms but may be at a higher risk for cognitive decline is a very important step toward developing new ways for doctors to detect [AD],” Resnick and Scheltens wrote.

The study researchers 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.

Dickerson BC, Wolk DA. Neurology. 2012; 78: 84–90.

Resnick SM, Scheltens P. Neurology. 2012; 78: 80–81.