It may soon be easier to predict which patients 65 and older will develop Alzheimer's disease and other dementias, researchers said.
A 15-point index including both conventional and newly identified risk factors for the conditions correctly classified 88 percent of patients according to their risk of developing dementia within six years, Deborah Barnes of the University of California San Francisco and colleagues reported online in Neurology.
More than half of patients with a high score -- 56 percent of them -- developed some form of dementia, compared with 4.2 percent of those with a low score and 22.8 percent of those who fell in between.
The possibility that a tool could pinpoint the risk of developing Alzheimer's disease is an intriguing concept, especially since it is now estimated that every 70 seconds someone develops the condition, according to the Alzheimer's Association. The association further estimates that about 5.3 million Americans are living with Alzheimer's.
The factors included in the index that best predicted whether a patient would develop dementia were older age, lower scores on two tests of cognitive function, presence of at least one of the known genetic variations linked to Alzheimer's, below-normal weight, abstinence from alcohol, a history of coronary artery bypass surgery, and a slow time putting on and buttoning a shirt -- a test of fine motor function.
The researchers also included in the index certain changes in the brain and arteries that could be detected through medical imaging.
A low score on the index might reassure patients and their families, the researchers said, and a high score might aid patients in making preparations for the future.
But Zaven Khachaturian, president and CEO of the Lou Ruvo Brain Institute in Las Vegas and a widely recognized authority in Alzheimer's Disease, said that before the tool could be used in clinical practice, physicians and patients would need more information about how to interpret the scores.
"At this stage, it would be prudent to use this test as a research tool, rather than as means to manage patients in general medical practice until further validation of the predictive utility of the test," he said.
Still, there are currently no tools to predict dementia risk late in life, Barnes and her colleagues said. A midlife index exists, but it assesses risk over the next 20 years.
To fill the gap, the investigators used data from 3,375 patients 65 and older who took part in the Cardiovascular Health Cognition Study. All were free from dementia at the beginning of the research.
Through six years of follow-up, 14 percent developed some form of dementia. Of those, 51 percent were diagnosed with Alzheimer's disease, 13 percent with vascular dementia, 31 percent with mixed dementia, and 5 percent with other types.
The index correctly identified patients who would experience dementia 56 percent of the time, and it was able to correctly rule out a person for dementia 90 percent of the time. All told, the test yielded the correct answer 88 percent of the time over the six years encompassed by the research.