Alzheimer’s Disease and the Role of Biomarkers
Alzheimer’s disease is a neurodegenerative condition that can cause difficulties with thinking, memory, and physical decline. Biomarkers can help experts monitor its development, progression, and response to treatment.
Alzheimer’s disease (often abbreviated as “Alzheimer’s”) primarily affects the brain.
Neurodegeneration — the progressive deterioration of nerve cells — occurs in Alzheimer’s when abnormal protein deposits, called beta-amyloid plaques and tau tangles, form in the brain.
Alzheimer’s is the most common cause of dementia, marked by a significant decline in cognitive ability that impairs daily functioning. Because Alzheimer’s typically emerges later in life, its early symptoms are often mistaken for natural age-related changes.
For this reason, biomarkers are becoming increasingly important in the treatment of Alzheimer’s. These measurable indicators can aid in early diagnosis and allow doctors to personalize Alzheimer’s management plans through careful monitoring.
What Are Biomarkers?
Biomarkers, or biological markers, are measurable indicators of bodily function. They encompass a variety of biological factors, from the level of specific molecules to visible changes in the structure of organs and tissues.
In disease management, biomarkers act as “red flags” indicating that a disease process, such as Alzheimer’s, is occurring, progressing, or responding to treatment.
Types of Alzheimer’s Biomarkers
Healthcare professionals can monitor Alzheimer’s through several biomarkers, including the following:
Amyloid-beta
Amyloid-beta is a protein byproduct produced during natural cellular metabolism. Elevated levels of this protein in the body are considered precursors and indicators of Alzheimer’s disease processes. Amyloid-beta protein plaques visible on diagnostic imaging are a hallmark feature of Alzheimer’s.
Tau Protein
Tau protein plays a crucial role in stabilizing the structure of neurons. In Alzheimer’s, tau protein dysfunction can lead to abnormal structural “tangles” inside neurons, which promote cell death. Elevated tau protein levels or visible deposits of this protein can provide insights into the development and progression of Alzheimer’s.
Neurofilament Light (NFL)
NFL is another type of structural protein found in neurons. When neurons are damaged or die, this protein is released into the cerebrospinal fluid (CSF), the colorless liquid that surrounds the brain and spinal cord. The presence of NFL in a CSF sample can indicate neurodegenerative processes, such as Alzheimer’s, are occurring.
Inflammatory Markers
The body’s inflammatory response involves multiple measurable substances, such as cytokines, proteins, and chemokines. Some of these pro-inflammatory substances, including interleukin-6, tumor necrosis factor-alpha, and C-reactive protein, have been linked to the development, progression, and therapeutic response of Alzheimer’s.
Are There Blood Biomarkers for Alzheimer’s?
Most biomarkers for Alzheimer’s are detected through cerebrospinal fluid (CSF) analysis or diagnostic imaging techniques. However, blood biomarkers are an area of ongoing research.
According to a 2023 research review, phosphorylated tau (p-tau) in blood plasma may be a promising blood biomarker that accurately distinguishes Alzheimer’s from other neurodegenerative conditions. P-tau is a tau protein that has undergone phosphorylation, a process in which phosphates combine with amino acids to regulate cellular functions.
While no blood biomarkers are currently used routinely in clinical practice, many are under investigation. Other blood biomarkers being evaluated include those that screen for specific beta-amyloid proteins and inflammatory indicators.
How Can Biomarkers Help Diagnose Alzheimer’s?
Biomarkers can be crucial diagnostic tools in a comprehensive Alzheimer’s disease assessment. They can indicate disease-related changes in the body before physical symptoms become noticeable or structural changes in the brain are visible through other tests. Additionally, biomarkers provide precise, specific information that can help distinguish one disease from another.
For example, the presence of amyloid-beta plaques can indicate Alzheimer’s rather than another type of dementia, such as frontotemporal dementia. These features make biomarkers invaluable in the early detection of Alzheimer’s disease and in differentiating its early stages from other forms of dementia that may have similar onset features.
Are There Any Currently Available Tests Using Biomarkers?
The following biomarker tests are currently available for the diagnosis of Alzheimer’s disease:
CSF Testing
CSF tests involve analyzing a sample of cerebrospinal fluid to measure levels of amyloid-beta and tau protein.
Neuroimaging
Diagnostic imaging tools are used to detect visible changes in the brain, such as the buildup of amyloid-beta plaques or the presence of tau tangles. These tests can also reveal overall changes in brain structure related to disease processes, such as brain atrophy or a decrease in tissue size and integrity.
Common neuroimaging tests include:
- MRI scans
- CT scans
- Positron Emission Tomography (PET) scans
- Fluorodeoxyglucose (FDG)-PET scans
Genetic Risk Profiling
Several genes may be involved in the pathology of Alzheimer’s disease, including the APOE-e4 gene, which is associated with the highest risk in certain groups of people. Genetic profiling can help doctors determine whether you have genetic variations associated with Alzheimer’s.
What Types of Tests Are Still Being Studied?
Biomarkers for Alzheimer’s are an area of ongoing research. While blood biomarkers continue to be a priority due to their accessibility and affordability compared to current methods, new diagnostic imaging strategies, genetic screenings, and novel detection techniques are also being explored.
Some experts believe that artificial intelligence (AI) and machine learning will eventually play a significant role in biomarker screening and the prediction of Alzheimer’s.