How Is Alzheimer's Disease Diagnosed?

Clinicians use a number of tools to diagnose possible Alzheimer's dementia (dementia that could be due to another condition) or probable Alzheimer's dementia (no other cause of dementia can be found). Some people with memory problems may have mild cognitive impairment (MCI), a condition that may lead to Alzheimer's disease. People with MCI have more memory problems than normal for people their age, but their symptoms are not as severe as those seen in Alzheimer's. Importantly, not all people with MCI go on to develop Alzheimer's disease, and some may even recover from MCI and regain normal cognition. This recovery may happen if MCI is due to a medicine's side effect or temporary depression, for example.

Tools for diagnosing probable Alzheimer's disease include a medical history, a physical exam, and tests-preferably over time-that measure memory, language skills, and other abilities related to brain functioning. Information provided by family members or other caregivers about changes in a person's day-to-day function and behavior also help in diagnosis.

Currently, the most definitive diagnosis of Alzheimer's is made after death, by examining brain tissue for plaques and tangles. However, in specialized research facilities such as NIA's network of Alzheimer's Disease Centers, clinicians may also use brain scans and biomarkers found in blood and cerebrospinal fluid to help diagnose Alzheimer's dementia in people, who may or may not be participating in a clinical trial.

Early, accurate diagnosis is crucial because it tells people whether they have Alzheimer's disease or something else. Stroke, tumor, Parkinson's disease, sleep disturbances, or side effects of medications are all known to affect cognitive function and memory, and some of these conditions are reversible. When Alzheimer's is diagnosed, knowing early on can help families plan for the future, while the person with the disorder can still participate in making decisions.

Researchers are developing tests using biomarkers to detect the disease before memory loss or cognitive impairment is evident. One day these tests could be used in general medical practice.