November 01, 2015

Alzheimer's biomarkers

Identifying early clues

ScansWhen you think of Alzheimer's disease, you might think of the characteristic signs and symptoms of late-stage dementia, such as profound memory loss and the inability to carry out simple daily activities.

But more and more, scientists are coming to believe that thedisease starts long before signs and symptoms appear. This phase is referred to as preclinical Alzheimer's disease. By the time people become aware of the signs and symptoms of dementia, the disease is already well-established.

Many Alzheimer's researchers are now focusing their efforts on trying to detect the disease in its earliest stages. The hope is that early detection will allow for the development of more-targeted and more-effective treatments — before irreparable harm has been done to the brain.

Looking for signs

Until recently, Alzheimer's disease could only be diagnosed with complete accuracy after death. Microscopic ­examination of the brain during autopsy reveals an overabundance of abnormal structures in the brain. These classic characteristics include clumps of amyloid protein (amyloid-beta plaques) around nerve cells and clusters of tangled protein threads (neurofibrillary tangles) within the nerve cells.

Plaques and tangles are considered biomarkers of Alzheimer's disease. A biomarker is a measurable substance in the body that acts as a signpost, often for the presence of disease — although it also can be used to mark a normal biologic process or a response to therapy. For example, elevated cholesterol levels are a biomarker for cardiovascular disease.

What's exciting about the new research is that scientists are finding a number of biomarkers...