Medicine

Doctors Can't Definitively Diagnose Alzheimer's Until After Death

Alzheimer's disease (AD) is the sixth leading cause of death in the United States, affecting one in nine seniors — at least, we think. The only way doctors can diagnose the disease beyond a shadow of a doubt is with an autopsy. That's why researchers are hard at work developing tests that can not only definitively diagnose the disease, but catch it early, when there's still a chance to help.

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Doing The Best We Can

Doctors will still diagnose Alzheimer's disease, just not with 100 percent certainty. While a person is still alive, they'll perform a battery of physical and cognitive tests to determine whether their dementia is likely from AD — in which case they may diagnose "possible" or "probable Alzheimer's dementia" — or from some other problem. But that requires visible symptoms that may only show up when it's too late to start preventative measures. There's no cure for the disease, but some therapies are showing promise in at least slowing its progress.

The reason a definitive diagnosis requires an autopsy is that the disease's defining characteristics are microscopic changes in the brain tissue itself. During an autopsy, diseased brain tissue under the microscope may show plaques, abnormal clusters of beta-amyloid protein fragments that build up between nerve cells. Dying nerve cells also contain tangles, twisted strands of tau proteins that keep nutrients from moving through the cells. Overall, brains with Alzheimer's have fewer nerve cells and synapses than healthy brains, and can often look smaller and shriveled.

A Brighter Future

Luckily, plaques and tangles leave telltale signs in the blood. If researchers could come up with a blood test for these markers, doctors might be able to diagnose Alzheimer's definitively — and much, much sooner. In 2014, Georgetown University researchers announced the development of a test that could predict with 90 percent accuracy if a healthy person would develop either mild cognitive impairment or Alzheimer's disease within three years.

And in 2017, a team from Lancaster University in England successfully used "vibrational spectroscopy" — a technique that analyzes everything in a biological sample by creating a light spectrum "fingerprint" — to not only diagnose Alzheimer's disease in a large number of patients, but accurately differentiate between it and other similar diseases. There's still a long road and more breakthroughs ahead for Alzheimer's diagnosis, but the future is looking brighter.

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Alzheimer's And The Brain

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Key Facts In This Video

  1. Dementia involves a decline in cognitive skills used to perform everyday activities. 60-80% of dementia cases are Alzheimer's disease. 02:22

  2. Here's how chromosome 21 may play a role. 09:19

  3. Physical activity, a heart-healthy diet, learning a second language, being social, protecting your head, and intellectual activities all may lower your risk for AD. 12:19

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