Unlocking the Brain’s Clues to Alzheimer’s Risk

Published on February 1, 2023

Imagine you’re an investigator, searching for clues that could lead to the prevention of Alzheimer’s disease. One clue you stumble upon is subjective cognitive decline (SCD), which might be a precursor to AD dementia. But does SCD correspond to changes in the brain’s structure and function before symptoms even appear? That’s what this study set out to investigate. By studying middle-aged adults with a family history of AD dementia, researchers used magnetic resonance imaging (MRI) to examine the relationship between SCD and brain measures. They discovered that APOE ε4 carriers, a group with a higher risk of developing AD, showed signs of greater brain alterations when they experienced higher levels of SCD. Specifically, they had increased activation in certain frontal cortices and decreased connectivity in the uncinate fasciculus. These findings suggest that SCD may serve as an early indicator of impending AD pathology, especially in individuals carrying the APOE ε4 allele. The study emphasizes the potential clinical value of identifying SCD as a means for early intervention and participant selection in AD prevention clinical trials. It’s a crucial piece in our ongoing puzzle to unlock the secrets of Alzheimer’s!

IntroductionRecently, interest has emerged in subjective cognitive decline (SCD) as a potential precursor to Alzheimer’s disease (AD) dementia. Whether individuals with SCD harbor brain alterations in midlife, when AD-related pathology begins, is yet to be elucidated. Furthermore, the role of apolipoprotein ε4 (APOE ε4) allele, a robust AD risk factor, in the relationship between SCD and brain alterations is unknown. We examined whether APOE genotype modulates the association of SCD with brain measures in individuals at high AD risk.MethodsMiddle-aged adults with parental history of AD dementia underwent magnetic resonance imaging (MRI) and the Memory Functioning Questionnaire. Regression analysis tested the extent to which SCD was associated with activation during an functional MRI (fMRI) working-memory task, and white-matter microstructure. APOE ε4 genotype was tested as a moderator.ResultsAmong APOE ε4 carriers, but not among non-carriers, SCD was associated with higher activation in the anterior cingulate (p = 0.003), inferior, middle, and superior frontal cortices (p = 0.041, p = 0.048, p = 0.037, respectively); and with lower fractional anisotropy in the uncinate fasciculus (p = 0.002), adjusting for age, sex, and education.ConclusionIn middle aged, cognitively normal individuals at high AD risk, higher SCD was associated with greater brain alterations possibly reflecting incipient AD pathology. When accompanied by a family history of AD and an APOE ε4 allele, SCD may have important clinical value, allowing a window for early intervention and for participants’ stratification in AD prevention clinical trials.

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