New York: For the first time in 25 years, medical experts are proposing a major change in the criteria for Alzheimer's disease, part of a new movement to diagnose and, eventually, treat the disease earlier.
The new diagnostic guidelines, presented Tuesday at an international Alzheimer's meeting in Hawaii, would mean that new technology like brain scans would be used to detect the disease even before there are evident memory problems or other symptoms.
If the guidelines are adopted in the fall, as expected, some experts predict a two- to threefold increase in the number of people with Alzheimer's disease. Many more people would be told they probably are on their way to getting it. The Alzheimer's Association says 5.3 million Americans now have the disease.
The changes could also help drug companies that are, for the first time, developing new drugs to try to attack the disease earlier. So far, there are no drugs that alter the course of the disease.
Development of the guidelines, by panels of experts convened by the National Institute on Aging and the Alzheimer's Association, began a year ago because, with a new understanding of the disease and new ways of detection, it was becoming clear that the old method of diagnosing Alzheimer's was sorely outdated.
The current formal criteria for diagnosing Alzheimer's require steadily progressing dementia -- memory loss and an inability to carry out day-to-day activities, like dressing or bathing -- along with a pathologist's report of plaque and another abnormality, known as tangles, in the brain after death.
But researchers are now convinced that the disease is present a decade or more before dementia.
"Our thinking has changed dramatically," said Dr. Paul Aisen, an Alzheimer's researcher at the University of California, San Diego, and a member of one of the groups formulating the new guidelines. "We now view dementia as a late stage in the process."
The new guidelines include criteria for three stages of the disease: preclinical disease, mild cognitive impairment due to Alzheimer's disease and, lastly, Alzheimer's dementia. The guidelines should make diagnosing the final stage of the disease in people who have dementia more definitive. But, the guidelines also say that the earlier a diagnosis is made the less certain it is. And so the new effort to diagnose the disease earlier could, at least initially, lead to more mistaken diagnoses.
Under the new guidelines, for the first time, diagnoses will aim to identify the disease as it is developing by using results from so-called biomarkers -- tests like brain scans, M.R.I. scans and spinal taps that reveal telltale brain changes.
The biomarkers were developed and tested only recently and none have been formally approved for Alzheimer's diagnosis. One of the newest, a PET scan, shows plaque in the brain -- a unique sign of Alzheimer's brain pathology. The others provide strong indications that Alzheimer's is present, even when patients do not yet have dementia or even much memory loss.
Dr. Aisen says he foresees a day when people in their 50s routinely have biomarker tests for Alzheimer's and, if the tests indicate the disease is brewing, take drugs to halt it. That is a ways off but, he said, but "it's where we are heading."
"This is a major advance," said Dr. John Morris, an Alzheimer's researcher at Washington University in St. Louis who helped formulate the guidelines. "We used to say we did not know for certain it was Alzheimer's until the brain is examined on autopsy."
Dr. Ronald Petersen, an Alzheimer's researcher at the Mayo Clinic in Minnesota and chairman of the Alzheimer's Association's medical and scientific advisory council, said adding biomarkers to a diagnosis would be a big improvement.
Today, he says, when a patient comes with memory problems, doctors might say that the person has a chance of developing Alzheimer's in the next decade, a chance of not getting much worse for several years, and a chance of actually getting better.
Tests like brain scans, Dr. Petersen said, "will allow us to be much more definitive." If the tests show changes characteristic of Alzheimer's disease, a doctor can say, "I think you are on the Alzheimer's road."
That can be a difficult conversation, but it can allow patients and their families to plan. "At least it's a conversation the physician can have with the patient," Dr. Petersen said.
Alzheimer's experts welcomed the new criteria.
"Over all, I think this is a giant step in the right direction," said Dr. P. Murali Doraiswamy, a psychiatry professor and Alzheimer's disease researcher at Duke University who was not involved with making the guidelines. "It moves us closer to the cause of the disease rather than just looking at symptoms."
But, he added, it also is a huge change.
"This has implications for everybody alive, anybody who is getting older," Dr. Doraiswamy said. Among other things, he said, it will encourage a lot more testing. And, Dr. Doraiswamy said, "diagnosis rates, like testing rates, only go in one direction -- up."
Doctors will have to learn new terms -- preclinical Alzheimer's; prodromal, or early stage, Alzheimer's. Patients going to see a doctor with memory problems might be offered biomarker tests, which can be expensive.
The ripple extends beyond doctors and patients, Dr. Doraiswamy said. The new diagnostic criteria also have consequences for lawyers, insurance companies and workers' compensation programs.
And, he said, people have to be prepared for unintended consequences, which always occur when the diagnosis of a disease is changed. For now, he said: "We ought to be cautious that we don't stimulate all this testing before we can give people something to manage their disease. There is no point in giving them just a label."