(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 as a "spectrum" disease that would include even mild memory and behavioral symptoms.
The idea, proposed by the Alzheimer's Association and the National Institutes of Health, would create three stages of Alzheimer's, 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.
Current therapies usually don't make much difference. 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.
"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.
The newly expanded stages of Alzheimer's are meant to cover the full spectrum of the disease as it progresses over the years.
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.
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.
While it does not cripple a person's ability to function throughout the day, these differences are often noticed by friends and family members.
Not all cases of mild cognitive impairment develop into Alzheimer's. These problems could stem from other factors such as a drug's side effects or vascular disease.
This second stage, for now, is largely restricted to research, but could be used in specialized clinical settings.
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."