September 22, 2008
Older people who perform inconsistently on memory tests may be at increased risk for Alzheimer's disease, a preliminary new study suggest.
Most memory testing ranks individuals on a scale that compares them against healthy individuals. This approach, however, does not take into account variations in testing that occur with a single individual. Some people may show a lot of individual variation in memory and thinking tests over many months.
The current study, published in The Journal of the American Medical Association, aimed to look at whether individual variation in memory tests in a single individual predicted the later onset of Alzheimer's.
Researchers at the Albert Einstein College of Medicine in New York evaluated 897 individuals, age 70 or older. All were part of The Einstein Aging Study, an ongoing study of aging and dementia of people living in a New York Bronx neighborhood.
Every 12 to 18 months, the study participants underwent detailed neurological and neuropsychological evaluations. The researchers included tests for verbal IQ, attention, memory, and executive function, a measure of how well people can think and sort information. The tests were designed to measure the function of various parts of the brain involved in recall, memory and thinking.
Of the 897 participants, 61 people, or 6.8 percent, developed dementia during an average follow-up period of 3.3 years. Of those, 47 participants had Alzheimer's, and 18 had dementia related to blood-vessel problems in the brain. During the study, 128 individuals died, which would be expected for people this age. Of those, 18 had developed dementia.
The researchers found that people who performed inconsistently on the memory tests were at increased risk of developing Alzheimer's and other forms of dementia. They note that further testing in greater numbers of people of varying ages and physical conditions is required to confirm these findings. However, the findings do open up the possibility that charting an individual's performance on a variety of memory and thinking tests over time may offer new windows into diagnosing dementia earlier.
Current memory and thinking tests may detect problems up to seven years prior to the onset of Alzheimer's. Some people are found to have mild cognitive impairment, a form of memory loss that often precedes Alzheimer's. Alzheimer's may be a disease that takes many years, and even decades, to unfold, researchers speculate.
Developing better ways to test for Alzheimer's disease more accurately and at an even earlier stage is important. Experimental treatments for Alzheimer's now under development may be most effective in the very earliest stages of the disease process.
Roee Holtzer; Joe Verghese; Cuiling Wang; Charles B. Hall; Richard B. Lipton: "Within-Person Across-Neuropsychological Test Variability and Incident Dementia." Journal of the American Medical Association, Volume 300, Number 7, August 20, 2008, pages 823-830.