The first new U.S. diagnostic guidelines for Alzheimer's disease released in 27 years paint the disorder as a disease that occurs gradually over many years, starting with changes in the brain, then mild memory problems and finally progressing to full-blown dementia.
Released on Tuesday by the National Institute on Aging and the Alzheimer's Association, the guidelines officially recognize mild cognitive impairment or MCI -- first described more than a decade ago -- as a precursor to the disease.
And they add a new research category known as preclinical Alzheimer's, the earliest stage of the disease when clumps of a protein called amyloid are just beginning to form in the brains of people who are otherwise healthy.
This preclinical stage about 10 years before dementia sets in is seen as the best place to intervene in the disease. It is why new imaging agents for PET scans, spinal fluid tests and other so-called biomarkers that predict Alzheimer's are becoming so important to researchers and drug companies.
The notion of different stages of the disease marks a stark contrast from the last set of guidelines published by government researchers in 1984, which only recognized the dementia phase of Alzheimer's -- in which people lose their memories and the ability to care for themselves.
"The biggest difference between then and now is we now think of this process as a continuum that started many years before we make the diagnosis of dementia," Dr. Guy McKhann of Johns Hopkins University School of Medicine, who worked on the new guidelines, told a media briefing.
Including earlier phases of the disease is important in advancing Alzheimer's research, said Dr. Reisa Sperling of Brigham and Women's Hospital in Boston, who led the group that wrote the guidelines for preclinical Alzheimer's.
"If we are ever really going to move toward prevention of Alzheimer's disease, we have to include people who don't yet have symptoms," Sperling said in a telephone interview.
Saying the 'A' Word
"I think the real piece of that is not being afraid to say the 'A' word (Alzheimer's)," said Sperling, who acknowledged that the diagnosis is frightening.
"I believe what changed in cancer 10 or 20 years ago is when people became less afraid of using the 'C' word (cancer). I think we have to move to the same thing in Alzheimer's disease," she said.
Sperling said being able to diagnose someone with preclinical Alzheimer's will allow for much earlier treatment and prevention efforts, in much the same way as people with high cholesterol take statin drugs to prevent heart disease.
Both Sperling and Marilyn Albert of Johns Hopkins University School of Medicine in Baltimore, who worked on the guidelines for mild cognitive impairment, said biomarker tests, while promising, are not ready for prime time.
"The reason we think they should not be used in the doctor's office now is there is not a lot of standardization. We don't have a very good sense of what we call a cutoff point -- of what is normal and what is not," Albert said.
In January, advisers to the U.S. Food and Drug Administration rejected an Eli Lilly imaging agent, saying more data is needed before it can be approved for helping doctors rule out the presence of plaque linked to Alzheimer's disease.
Dr. John Ringman, an Alzheimer's researcher at the University of California, Los Angeles, who was not involved in drafting the guidelines, said defining the earlier phases of the disease gives researchers a common vocabulary.
"It's really a language researchers can use to talk to each other," he said.
Ringman said this will help companies select patients in earlier stages of the disease for clinical trials.
Many researchers believe most Alzheimer's drugs have failed because they were tried in people whose disease was too advanced to do any good.