Discoveries May Improve Identification of Alzheimer’s in African Americans
There’s some much-needed good news on the science horizon when it comes to older African Americans and Alzheimer’s disease, according to MedPage Today. This is a particularly salient development because African Americans have a significantly higher risk of Alzheimer’s disease, perhaps even twice as high than their non-Hispanic white counterparts.
In a study published in JAMA Network on Jan. 7 researchers from Washington University School of Medicine in St. Louis shared their findings that a common Alzheimer’s biomarker has a lower concentration in African Americans with a genetic predisposition to Alzheimer’s compared with whites with the exact same genetic predisposition. This specific genetic predisposition involves the APOE4 allele, or subtype, of the APOE gene. The APOE4 allele, which is found in roughly 10-15 percent of the population, increases the risk of Alzheimer’s and lowers the age of onset.
This understanding presents the possibility that healthcare providers may be failing to identify Alzheimer’s in African Americans when individual biomarkers are falling below the disease-indicator scale, a scale that is correlated primarily with how the biomarker manifests in whites.
A biomarker, short for a biological marker, is a predictable, measurable and accurate medical sign – such as body temperature, pulse, blood pressure, cholesterol and hormone levels, to name a few common ones – that’s used by healthcare professionals to confirm the presence of illness or health in a patient. Externally observable and quantifiable, biomarkers stand in contrast to symptoms, which are subjectively experienced and described by a patient, and that’s what makes biomarkers so useful and important.
One of the biomarkers for identifying Alzheimer’s disease is the concentration, or levels, of a protein called “tau” in the cerebrospinal fluid. Cerebrospinal fluid is the colorless liquid that surrounds the brain and spinal cord.
In healthy brains, tau protein provides structure and support for the transport of nutrients and molecules within the neurons. Neurons are highly-specialized nerve cells that form the foundation of our nervous system. Together, billions of neurons create a sophisticated intercellular communication network that sends and receives electrochemical signals within and between the brain, spinal cord and the rest of the body.
In an Alzheimer’s-affected brain, abnormally-high levels of tau protein accumulate and form clumps, known as “neurofibrillary tangles,” inside neurons. The neurofibrillary tangles obstruct transportation within the nerve cells which in turn blocks communication between neurons, contributing to the symptoms of cognitive decline. The tangles are one of three types of structural brain changes characteristic of Alzheimer’s, the other two being beta-amyloid plaques (protein clumps between the neurons) and chronic inflammation.
The study found no differences between African Americans and whites in cerebrospinal fluid concentrations of beta-amyloid protein.
Lead study co-author John Morris told MedPage Today that race-specific analyses and biomarker cut-offs are needed when it comes to tau protein level biomarkers. These tau protein biomarker differences, he said, may also be indicators of differences in the underlying biological mechanisms of Alzheimer’s disease as it occurs in African Americans compared with whites.
And finally, the findings “underscore the fact that, as a research community, we need to do a much better job of being welcoming to people of color,” Morris said. “Almost everything we’ve learned about Alzheimer’s disease in the past 35 years has come from studies in research participants who were almost totally white.”