Testing for Alzheimer's

Psychologists are searching for tests that can identify Alzheimer's disease even before symptoms appear.

To be effective, the medications currently available to treat Alzheimer's have to be used early on. But what's the best way to detect the disease before it's too late?

Psychologists have identified several promising tests:

  • Paired-associate learning test. In this test, people try to remember related pairs of words and unrelated pairs.For most people, it’s easier to remember the related word pairs. But people destined to develop Alzheimer’s disease don’t do any better when the words are related than when they’re not, according to findings from the Longitudinal Aging Study (PDF, 140 KB).

  • Perceptual identification task. People undergoing this test read words aloud as they appear briefly on a computer screen. Experimenters repeat some words to test for “priming,” a sense of familiarity that should allow test-takers to read those words faster. Priming doesn’t help people at high risk of developing Alzheimer’s, the Amsterdam researchers found. That’s a sign that these individuals aren’t learning as well as they should. 

  • Visual association test. In this test, people try to remember line drawings that have been illogically paired with other objects.Poor performance on this test suggests problems in episodic memory, according to the Amsterdam researchers.

  • Dichotic listening task. This test involves listening to information through headphones, with one stream of information going to the left ear and a different stream going to the right ear.People with early dementia do a better job of remembering information presented to the right ear, according to a study from Washington University's Alzheimer's Disease Research Center (PDF, 130 KB). The right ear is the default pathway for processing information.As dementia progresses, the researchers say, people have a harder time overriding the usual pathway and switching their attention to their left ears. As a result, the test is a good early-warning sign for Alzheimer’s.

Psychologists are also determining what tests aren’t as effective at predicting Alzheimer’s disease.

According to the Amsterdam researchers, for instance, the commonly used Mini Mental Status Exam is not as effective as other tests when it comes to predicting who will get Alzheimer’s.

The test can only distinguish between normal aging and Alzheimer’s when dementia is already in a more advanced state, they say.