Memory Can Decline Quickly Even Before Alzheimer’s Is Diagnosed

March 25, 2010 — Patients with mild cognitive impairment decline twice as fast each year compared with those with no cognitive problems, report researchers. Patients with Alzheimer’s disease decline roughly 4 times faster.

“The differences in rate of cognitive decline between Alzheimer’s disease and mild cognitive impairment underscore the clinical relevance of the progression to dementia,” report the researchers led by Robert Wilson, PhD, from Rush University Medical Center in Chicago, Illinois.

“While mild cognitive impairment and dementia clearly exist on a continuum, the accelerating cognitive deterioration in dementia is highly relevant to clinicians counseling patients and families with dementia,” they report.

The study is published in the March 23 issue of Neurology.

“The findings have important implications for understanding the relationships between the clinical manifestations and the pathology of Alzheimer disease,” David Knopman, MD, from the Mayo Clinic in Rochester, Minnesota, said in an accompanying editorial.

Investigators used data from the Chicago Health and Aging Project, a population-based study of people with an average age of 79 years, to quantify rates of decline in patients with incident Alzheimer’s disease or mild cognitive impairment. The work included more than 1150 people. Of these, 149 had Alzheimer’s disease, 395 had mild cognitive impairment, and 614 people had no memory problems.

Researchers administered 4 cognitive tests, from which they derived a composite measure of global cognitive function, first at the beginning of the study and then again every 3 years. The average follow-up was 5.5 years and up to 11 years.

Dr. Wilson and his team found the annual rate of decline was higher among patients with mild cognitive impairment and higher still among patients with Alzheimer’s disease.

Table. Composite Measure of Global Cognitive Decline

The result did not vary by race, sex, or age, they report.

Alzheimer’s disease has a devastating impact on cognition, even in its prodromal stages with comparable effects in African American and white people,” they noted.

The changes in rate of decline occur as the brain atrophies due to disease, editorialist Dr. Knopman added in a news release; first, decline occurs mainly in the hippocampus during the initial symptomatic stage and then in the temporal, parietal, and frontal cortex during the dementing illness phase of Alzheimer’s disease.

“The findings from the Chicago Health and Aging Project, combined with recent anatomical imaging results, provides a unique view of the spectrum of mild cognitive impairment and dementia of the Alzheimer’s type,” Dr. Knopman said in his editorial.

Other recent work reported by Medscape Neurology has focused on the concept of the continuum of disease in dementia. In a report published in the January issue of Alzheimer’s & Dementia, researchers led by Barry Reisberg, MD, from New York University in New York City, showed subjects who had subjective memory complaints but who were otherwise mentally healthy were 4.5 times more likely to develop mild cognitive impairment or dementia within about 7 years (2010;6:11-24).

This study was funded by the National Institute on Aging and the National Institute of Environmental Health Sciences. Coauthor Dr. Neelum Aggarwal has served on a scientific advisory board for Pfizer. Editorialist Dr. David Knopman serves on a Data Safety Monitoring Board for Lilly and is an investigator for clinical trials sponsored by Baxter, Elan, and Forest Pharmaceuticals. He also served as a consultant to GlaxoSmithKline for an Alzheimer agent.

SOURCE: www.medscape.com