Among persons with subjective cognitive decline, are Alzheimer biomarkers associated with a greater likelihood of progression to mild cognitive impairment or dementia?
In this meta-analysis, the presence of Alzheimer-associated biomarkers among adults with subjective cognitive decline was associated with an increased risk of progression to MCI or dementia. However, the overall progression risk was approximately 10% over 3 years and the biomarkers are not easily determined.
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The American Academy of Neurology guideline on managing persons with mild cognitive impairment (MCI), guided by systematic reviews, reported that the natural history of MCI is variable: 15% of patients will develop dementia within 2 years, and between 15% and 38% of patients with MCI will regress to normal. However, many adults with subjective cognitive decline don’t actually have MCI or dementia and are worried. These authors searched multiple sources to identify whether biomarkers can identify adults with subjective decline who are more likely to develop MCI or dementia. They identified 8 studies that included 1308 adults with subjective cognitive decline but without MCI or dementia. The studies had to have a baseline assessment of at least one biomarker associated with Alzheimer disease (amyloid, phosphorylated tau, total tau) and have at least 6 months of follow-up. The studies were at low risk of methodologic bias. During a mean follow-up of 3.3 years, the overall rate of progression to MCI or dementia was 10.5% (range = 1.5% - 37.8%). The biomarkers, of limited applicability in primary care settings, either came from cerebrospinal fluid assays, amyloid PET scans, or both. The presence of these biomarkers at baseline was associated with an increased risk of progression to MCI or dementia (amyloid odds ratio [OR] 5.89; 95% CI 2.33 - 14.90; phosphorylate tau OR 3.99; 2.34 - 6.85; total tau OR 2.26; 1.14 - 4.48) and there was moderate heterogeneity among the data. Only the amyloid data varied significantly among the studies. Since the biomarkers are not easily determined, the studies were likely to have included highly selected participants, and the results are likely to have limited applicability.
Henry C. Barry, MD, MS
Michigan State University
East Lansing, MI