What Is Alzheimer’s Disease and How Is It Diagnosed?

Alzheimer’s disease is a form of dementia characterized by abnormal protein clumps and tangles in the brain. It is a progressive – and for now, irreversible — disease that causes problems with memory, thinking and behavior.

What Is Alzheimer’s Disease?

Alzheimer’s disease is the most common type of dementia, a term used to describe memory loss and other cognitive issues. It accounts for 60 to 80 percent of dementia cases, and usually occurs in people 65 and older.

Alzheimer’s disease is not a normal part of aging. Rather, it is a degenerative brain disease that causes symptoms such as memory loss, impaired thinking, personality and mood changes, and eventually an inability to function.

Early Signs of Alzheimer’s Disease

Unable to learn new info: One of the most common early signs of Alzheimer’s disease is being unable to remember new information. Alzheimer’s usually begins in the area of the brain associated with learning, so having a hard time retaining newly learned information is typical at the onset.

Difficulty with math: Another symptom of Alzheimer’s includes difficulty with personal finances and numbers. If you’ve always been bad with math, then there’s no reason for alarm. But if you could previously balance your checkbook and now have difficulty with that or other simple mathematics, it could be a sign of the disease.

Forgetting words: Being unable to recall words for everyday objects.

Alzheimer’s Disease Symptoms and Stages

Because Alzheimer’s disease is a progressive degenerative disease, symptoms begin mildly and get worse over time. There are seven stages of Alzheimer’s disease, each with their own set of symptoms. (You can download the 7 stages chart and how to manage each stage here.)

As Alzheimer’s disease advances, so do the symptoms. Common Alzheimer’s symptoms include: forgetting names and words, losing things, difficulty planning and organizing, poor short-term memory, difficulty with math, forgetting details of your life, disorientation, mood and behavior changes including depression, withdrawal and agitation, inability to recognize faces, false suspicions about people, and eventually difficulty performing everyday tasks like dressing, walking, speaking and swallowing.

People with Alzheimer’s disease don’t always recognize that they are having memory issues. That’s why it’s important for loved ones to point out their concerns and act as a healthcare advocate at their doctor’s appointments.

How Is Alzheimer’s Disease Diagnosed?

Diagnosing Alzheimer’s and mild cognitive impairment, the stage that usually precedes Alzheimer’s, is an inexact science. Currently, an Alzheimer’s diagnosis is based on a series of tests and interviews that assess symptoms like memory loss. However, studies have shown that the tests used to diagnose Alzheimer’s are not precise.

Related: Alzheimer’s Tests: What Tests Are Available and How Accurate Are They?

According to a 2017 study published in Alzheimer’s & Dementia: Translational Research & Clinical Interventions, Alzheimer’s disease is misdiagnosed 24 percent of the time.

A group of researchers hopes to change that by looking at biomarkers, or the physical signs of Alzheimer’s in the brain, which could entirely change the way Alzheimer’s is diagnosed—and who gets a diagnosis.

Alzheimer’s-related changes in the brain often start decades before a patient gets noticeable symptoms. A diagnosis that relies on these physical changes would allow doctors to get a much faster picture of who will go on to develop the symptoms of Alzheimer’s.

Related: What is the Difference Between Dementia and Alzheimer’s? 

Alzheimer’s Changes in the Brain

What is Alzheimer’s disease from a biological perspective? A person with Alzheimer’s disease will have three distinct biomarkers, say researchers: an accumulation of brain beta-amyloid, the sticky protein that forms into plaques in Alzheimer’s disease; tau, another protein that forms into tangles that block neuron communication in Alzheimer’s disease; and overall neurodegeneration, which can result from a number of causes, like natural aging or brain injury.

Under the new proposed diagnostic criteria, developed by the National Institute on Aging and the Alzheimer’s Association, only a person with both tau and beta-amyloid would be officially diagnosed with Alzheimer’s disease.

“We have to focus on biological or physical targets to zero in on potential treatments for Alzheimer’s,” explained Eliezer Masliah, M.D., director of the Division of Neuroscience at the NIA. “By shifting the discussion to neuropathologic changes detected in biomarkers to define Alzheimer’s, as we look at symptoms and the range of influences on development of Alzheimer’s, I think we have a better shot at finding therapies, and sooner.”

While the new diagnosis criteria help explain what is Alzheimer’s, they aren’t meant to answer everything about how Alzheimer’s works.

We still don’t know what exactly causes the symptoms of Alzheimer’s, though most scientists believe it’s a combination of beta-amyloid and tau tangles. However, by classifying people early, scientists should be able to track whether amyloid and tau build-up just happens to occur alongside the disease, or whether it causes Alzheimer’s in the first place.

“With the aging of the global population, and the ever-escalating cost of care for people with dementia, new methods are desperately needed to improve the process of therapy development and increase the likelihood of success,” said Maria Carrillo, Ph.D., Alzheimer’s Association chief science officer. “This new research framework is an enormous step in the right direction for Alzheimer’s research.”

These new guidelines appeared in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.