Rochester, Minnesota - When you think of dementia, most people automatically think of Alzheimer's disease, too. But, under a new definition of Alzheimer's, the two terms no longer will be considered interchangeable.

The new definition is part of a new framework for researching Alzheimer's disease that the Alzheimer's Association and the National Institute on Aging developed and released.

"Alzheimer's disease is one cause of dementia," Dr. Clifford Jack Jr., a Mayo Clinic radiologist and Alzheimer's researcher, says. "It's the most common cause, but it's certainly not the only cause. And that has been a source of major confusion."

Dr. Jack helped lead a team of scientists with the Alzheimer's Association and the National Institute on Aging release the new Alzheimer's research framework.

Currently, Alzheimer's is diagnosed by evaluating symptoms and cognitive behavior associated with the disease. But, Dr. Jack says, that can be misleading for research.

So, in the new research framework, Alzheimer's disease is not diagnosed based on symptoms. Instead, it is diagnosed by its neuropathology, referred to as plaques and tangles. This can be done at autopsy or using biomarkers when a person is still living. That means through cerebral spinal fluid or through brain imaging.

Dr. Jack says the change is significant.

"What we're saying is that symptoms are a consequence of the disease," he says. "They're not the definition of the disease. People can have the pathology in the brain and be symptom-free. They still have the disease even though they have no symptoms. If they have the pathology, they have the diseases. It's controversial in some circles because, historically, the presence of symptoms was the definition. Now we're saying [that's] no longer so."

Dr. Jack says changing the definition allows research to better target patients so clinical trials will be more effective.

He also says this change is significant because it can allow researchers to diagnose Alzheimer's disease before a patient has symptoms. This will allow scientists to develop treatments that stop Alzheimer's before symptoms develop, improving the quality of life for patients.

Dr. Jack says a good way to think of the shift is comparing it to how health care providers treat heart disease.

"The best way to treat cardiovascular disease is by giving an asymptomatic person statins, you know, for 20, 30 years, as opposed to waiting until that person has a stroke or heart attack, and then trying to treat [that]," he says. "So that's the ... and it's only by defining the disease in this way, biologically, that you can identify treatments that prevent the onset of symptoms."

Dr. Jack says he and the other scientists releasing the new framework hope it will create a common language for researchers to use in the short term.

"The long term is that these biomarkers – classifying people in this way, defining Alzheimer's disease in this way, using biomarkers to determine who actually gets into clinical trials – that will lead to more rapid development and identification of treatments," he says. "And, so, the long term is that this biomarker-based definition will lead more rapidly to effective treatments."