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Cognitive Tests May Identify People At Risk Of Developing Alzheimer's Disease

CHICAGO, IL -- September 19, 2001 -- Cognitive tests may identify patients at risk for progression to Alzheimer's disease (AD) years prior to the onset of dementia, according to an article in the September issue of the Archives of General Psychiatry, a member of the Journal of the American Medical Association family of journals.

Peijun Chen, M.D., from the University of Pittsburgh Graduate School of Public Health, and colleagues completed a 10-year follow-up study of 551 people older than 65 who had no evidence of dementia at the time of study enrollment.

The authors compared changes over time on a spectrum of cognitive tests between two groups: 68 cases who subsequently developed systematic AD and 483 controls who remained non-demented. The researchers evaluated test results to identify specific patterns of cognitive decline and to calculate the degree of decline on each test in patients with pre-symptomatic AD compared with those with normal aging.

The researchers found that two cognitive functions, memory and executive dysfunction, showed the greatest decline over time in individuals who clinically manifested AD 1.5 years later. Executive functions control the execution of complex, goal-directed activities. "In our sample, cognitive decline in pre-symptomatic AD was not uniform across cognitive domains. Memory functions ... and executive functions ... declined the most prominently," the researchers state.

"Because memory deficit is a cardinal diagnostic feature of AD, it was confirmatory rather than surprising to find in our own study, as in those of others, that early memory impairment was associated with subsequent onset of AD. However, consensus is lacking on the sequence of the cognitive deficits that follow, precede or coexist with memory impairment during progression of the disease, particularly early in the course," the authors comment. The researchers suggest that their research may facilitate early detection of AD.

According to background information in the article, it is difficult to determine how long the underlying pathological disorder has been present before Alzheimer's disease is clinically manifested. If physicians had a reliable, objective means of detecting AD early, very mild cognitive impairments could be identified as signs of pre-symptomatic or pre-clinical AD. This would allow intervention before the first symptoms appear.

"These findings might help us understand the underlying evolution of the early neuro-degenerative process. They highlight the importance of executive dysfunction early in the disease process and might facilitate early detection of AD," the authors conclude.

SOURCE: Archives of General Psychiatry

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