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

They compared changes over time on a range of cognitive tests between two groups: 68 cases who subsequently developed AD and 483 controls who remained nondemented.

The researchers evaluated test results to identify specific patterns of cognitive decline and to calculate the amount of decline on each test in patients with presymptomatic AD compared with those with normal aging.

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 complex goal-directed activities.)

"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 study may facilitate early detection of AD.

It has been 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 presymptomatic or preclinical AD. This would allow intervention before the first symptoms appear.

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

The study was supported in part by grants from the National Institute on Aging of the National Institutes of Health.

(Reference: Arch Gen Psychiatry. 2001;58:853-858)

In an accompanying editorial, Brent J. Small, Ph.D., from the University of South Florida in Tampa and colleagues write: "We are excited by the fact that in the past year, four studies have been published that have examined longitudinal changes in cognitive performance during the preclinical phase of AD.

"In the future, we may be able to identify persons at risk of developing AD and administer prophylactic treatments to achieve significant gains in delaying or stopping the progression of this disease."

(Reference: Arch Gen Psychiatry. 2001;58:859-860)

20-Sep-2001