A biological marker (biomarker) is a measurable substance in an organism whose presence is indicative of some phenomenon such as disease or infection. Biomarkers can help doctors and scientists diagnose diseases and health conditions, find health risks in a person, monitor responses to treatment, and see how a person's disease or health condition changes over time.

Biomarkers can show early indications of biological changes associated with Alzheimer’s disease (AD). AD may begin causing gradual changes in the brain some 10-20 years before the onset of symptoms.  

The best hope of stopping AD is before symptoms appear, and the need for earlier treatment makes biomarkers so important.


A series of brain scans.

Biomarkers and Alzheimer’s Disease

Scientists are searching for an “AD signature” using biomarkers. Said another way, scientists are looking for earlier signs of AD that aren’t visible to the naked eye by studying many types of biomarkers. In the future, a biomarker test could:

  • Allow for a proper clinical diagnosis earlier before symptoms are visible.
  • Provide reliable measures of how the disease progress in a particular patient.
  • Guide treatment decisions.  When drugs become available, determining such things as who needs treatment, when to start, and which drugs and treatment strategies are most likely to be successful.
  • Be used by doctors to monitor response to treatment.

It is now widely accepted that distinct subtypes of Alzheimer’s exist. Biomarkers may help distinguish between these different types of the disease and help inform optimal patient-specific treatment options.


What types of biomarkers are being studied? 

In Alzheimer's and other forms of dementiaprimary biomarkers are toxic proteins associated with the disease – like amyloid-beta and tau. These can be detected using neuroimaging scans such as PET or MRI, or by testing the cerebrospinal fluid or more recently, blood.  

The goal is to find the least invasive, earliest measures that might be able to detect the probability of disease. More novel biomarker assessments are being developed that use the eye to detect changes in the brain as well as driving or walking patterns that may serve as earlier detectors of disease.


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