Awareness of memory impairment starts deteriorating about 2.6 years before a diagnosis of dementia, a new study shows.
Researchers also found that this deterioration is a manifestation of dementia-related pathology, such as tau tangles and gross cerebral infarcts.
“It’s important to try to understand what the process of dementia is and what it feels like from the inside out,” said lead author Robert Wilson, PhD, professor, Neuropsychology, Rush University Alzheimer Disease Center, Chicago, Illinois.
The analysis was based on data from three ongoing longitudinal clinical pathologic studies of older patients who at the time of enrollment were at least 50 years old and did not have cognitive impairment.
These studies included the Religious Orders Study, which began in 1994 and includes older Catholic nuns, priests, and brothers across the United States; the Rush Memory and Aging project, which got underway in 1997 and includes older people from the Chicago area; and the Minority Aging Research Study, which started in 2004 and enrolls older black people from metropolitan Chicago.
Every year, study participants underwent a battery of 19 cognitive tests, including measures of episodic memory, semantic memory, and working memory. At every annual exam, they were also asked how often they had trouble remembering things and how their memory compared to a decade before.
The researchers put together a composite rating of how participants thought their memory was and compared this with their actual performance on memory tests over time.
“We sort of got a measure of the mismatch between their rating and their performance each year,” said Dr Wilson. “Statistically, if that number is 0, it means there is a pretty good correspondence between their rating and performance. As it dips down below 0, they are over-rating their memory.”
The analysis included 2092 participants, who had a mean baseline age of 76.1 years and a mean of 7.7 years of follow-up. In this group, this “mismatch” measure at baseline was a mean of 0.016, which suggested no systematic tendency to overestimate or underestimate memory ability at that time.
Researchers looked at a subset of 239 participants with at least four annual evaluations who developed dementia. They determined that starting a mean of 2.6 years before their dementia onset, their episodic memory awareness began to sharply decline.
This article has kindly been shared with us by Medscape Medical News.