Editor's note: Larry King returns to CNN with an emotional look at how people cope with Alzheimers disease. Don't miss "Unthinkable: the Alzheimer's Epidemic," Sunday night, May 1st at 8 ET on CNN.

(CNN) -- Alzheimer's disease begins long before family and friends notice differences in the patient's memory and behavior, doctors who treat the condition said Monday. By the time an official diagnosis is made, the person's function is usually significantly impaired and treatment rarely helps.

Doctors are suggesting a redefinition of Alzheimer's that would include even mild memory and behavioral symptoms. Disease experts expect an increase in the number of patients receiving the Alzheimer's diagnosis as a result of the change.

The idea, proposed by the Alzheimer's Association and the National Institutes of Health, would define Alzheimer's as a "spectrum" disease, creating three stages ranging from lesser to greater severity in hopes that the devastating neurological condition could be detected earlier.

In the U.S., 5.4 million people have an Alzheimer's diagnosis. By 2050, that number is expected to more than triple.

The aim of identifying the disease earlier is to get patients in the pipeline for research for future treatment. When the disease isn't identified until later in its progression, patients are more impaired and treatments are even less effective, doctors said. Current therapies usually don't make much difference, doctors acknowledged in a media briefing Monday.

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"It's critically important when we have effective drugs to intervene as quickly as possible," said Marilyn Albert, professor of neurology at Johns Hopkins University School of Medicine, who helped formulate the new guidelines. "There could be drugs available now, but we're using them too late in the disease course.

"The goal in the field is to find people earlier, so when new treatments are developed, we can use them."

The new guidelines appear Tuesday in the journal Alzheimer's & Dementia.

The original criteria for Alzheimer's disease, written in 1984, defined the disease in a single stage and assumed people who didn't have symptoms did not have the disease. This original definition addressed only later stages of the disease, when it ravages the patient's ability to function.

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The newly expanded stages of Alzheimer's are meant to cover the full spectrum of the disease as it progresses over the years.

"For people working with Alzheimer's patients day-to-day, it doesn't make a huge difference in practice right now," said Dr. Neil Kremen, unit chief at the Geriatric Psychiatry Inpatient Unit at Zucker Hillside Hospital in New York.

Most doctors working with Alzheimer's have already accepted that the disease is a progression.

"People who work in the field have known this," he said about various stages of Alzheimer's. "It has been accepted. It was never codified into a standard guideline. In some sense, it's the formalization of things that people already know."

The stages have been divided into preclinical Alzheimer's, mild cognitive impairment and dementia.

First stage: Preclinical Alzheimer's disease

This stage is for research purposes only and will have no effect in your doctor's office.

The idea is that patients could be developing Alzheimer's, even when they are free of cognitive or memory problems.

This stage is to help researchers determine whether there is a biological change caused by Alzheimer's that can be detected through blood, spinal fluid test or neuroimaging. Right now, there is no test that accurately predict whether a person will develop Alzheimer's disease.

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While studies show that Alzheimer's patients experience changes in the brain -- the buildup of amyloid protein tangles and nerve cell changes -- it is unknown whether this means an inevitable progression to Alzheimer's dementia.

"Changes in their brain can be measured, but we can't predict for sure whether they're going to have the clinical disease," said Dr. Creighton Phelps, director of the Alzheimer's Disease Centers Program of the National Institutes of Health.

These tests are used only in research settings.

Scientists are working to develop a more definitive test or a scan to determine Alzheimer's risk.

Second stage: Mild cognitive impairment (MCI)

Long before a person gets an Alzheimer's diagnosis, he or she may show small changes in memory, behavior and thinking. This is called mild cognitive impairment.

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While it does not cripple a person's ability to function throughout the day, these differences are often noticed by friends and family members.

Some patients in this stage are already observed by their doctors as "probable Alzheimer's."

This is a gray area because not all memory problems are Alzheimer's-related. Cognitive difficulties could stem from other factors such as a drug's side effects or vascular disease.

This stage could be used in specialized Alzheimer's clinics. A specialist might determine that the cognitive problems are caused by underlying Alzheimer's disease after a comprehensive exam, based on the disease process and symptoms, said Dr. John C. Morris, director and principal investigator of the Alzheimer's Disease Research Center at the Washington University School of Medicine.

But there are no blood or medical tests available in doctors' offices to confirm whether the mild cognitive impairment is because of Alzheimer's.

Third stage: Dementia because of Alzheimer's

This is the stage when memory, thinking and behavioral symptoms have become so damaging that the patient's ability to function is hindered.

The disease is not solely restricted to memory problems. The new guidelines include other symptoms such as difficulty finding words, visual and spatial problems, impaired reasoning and judgment.

This is the stage that people are most familiar with. The patient eventually becomes unable to carry out basic daily tasks -- eating, bathroom-related functions and is fully dependent on others for basic care.

The purpose of setting out these updated stages of Alzheimer's is aimed at the future, Creighton said, to "define a research strategy for people who may be at risk for Alzheimer's."

Resources:

Alzheimer's Association

National Institute on Aging

Caring.com -- Simplifying caregiving, supporting caregivers

