A proposed new definition of Alzheimer’s disease unveiled Tuesday represents “a major evolution in how we think about Alzheimer’s,” according to the Alzheimer’s Association, but it will “increase dramatically” the number of people considered to have the disease, according to one researcher involved in its development.

“NIA-AA Research Framework: Towards a Biological Definition of Alzheimer’s Disease,” by the National Institute on Aging and the Alzheimer’s Association, was published in the April issue of Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.

The new definition includes those who have certain measurable changes in their brains in addition to those now thought to have the disease, who have outward signs of memory loss and other cognitive and behavioral symptoms. The change in definition, the researchers said, recognizes that Alzheimer’s disease may begin decades before those outward signs of decline appear.

The authors said they “take the position that biomarker evidence of Alzheimer’s disease indicates the presence of the disease whether or not symptoms are present, just as an abnormal HbA1C indicates the presence of diabetes whether or not symptoms are present.”

This type of approach also is used to define bone mineral density, hypertension and other conditions, they noted.

But it also will “increase dramatically” the number of people considered to have Alzheimer’s disease, Clifford R. Jack Jr., M.D., of the Mayo Clinic in Rochester, NY, who was the first author on the paper, told the Associated Press.

Once validated, the new way of thinking about Alzheimer’s could speed the development of drugs and other treatments for the disease, because the disease process and the sequence of events that occur before cognitive impairment will be better understood, according to the researchers.

For now, the framework is intended only for use by researchers in clinical, observational and natural history studies, not for clinicians, they said. And its use should not restrict alternative approaches to Alzheimer’s research, the authors added.

“It is called a ‘research framework because it needs to be thoroughly examined — and modified, if needed — before being adopted into general clinical practice,” Jack said. “Importantly, this framework should be examined in diverse populations.”