Morris JC, et al. - In this study, the authors investigated the existence of racial variations in molecular biomarkers for Alzheimer disease. Overall, they noted a differential impact of low tau and phosphorylated tau₁₈₁ in the cerebrospinal fluid (CSF) of African American individuals vs white individuals as these variants reflected a notable race by apolipoprotein E (APOE) ε4 interaction. According to findings, examination of molecular biomarkers of Alzheimer disease should adjust for the race.

Methods

• In the longitudinal studies, the investigators evaluated 1,255 study participants, including 173 African Americans, from January 1, 2004, to December 31, 2015, at the Knight Alzheimer Disease Research Center at Washington University, and completed a magnetic resonance imaging study of the brain and/or positron emission tomography of the brain with Pittsburgh compound B (radioligand for aggregated amyloid-β) and/or CSF assays for the concentrations of amyloid-β42, total tau, and phosphorylated tau₁₈₁.
• They conducted independent cross-sectional analyses from April 22, 2016, to August 27, 2018, for each biomarker modality with an analysis of variance or analysis of covariance including age, sex, educational level, race, APOE ε4 allele status, and clinical status (normal cognition or dementia).
• They conducted all biomarker assessments without knowledge of the clinical status of the participating individuals.
• Hippocampal volumes adjusted for differences in intracranial volumes, global cerebral amyloid burden as transformed into standardized uptake value ratios (partial volume corrected), and CSF concentrations of amyloid-β42, total tau, and phosphorylated tau₁₈₁ were the primary consequences.

Results

• They observed that 67.1% of African American study participants and 66.9% of non-Hispanic white candidates had normal cognition.
• They found no racial differences in the frequency of cerebral ischemic lesions noted on consequences of brain magnetic resonance imaging, mean cortical standardized uptake value ratios for Pittsburgh compound B, or for amyloid-β42 concentrations in CSF.
• Mean (SE) total hippocampal volumes were lower for African American individuals vs white participants in those with a recorded family history of dementia.
• The researchers observed that mean (SE) CSF concentrations of total tau were lower in African American participants vs white individuals, as were mean (SE) concentrations of phosphorylated tau₁₈₁.
• A notable race by APOE ε4 interaction for both CSF total tau and phosphorylated tau₁₈₁ was observed such that only APOE ε4–positive candidates exhibited the racial variations.