A new study suggests that the relationship between brain shrinkage and memory loss in Alzheimer's disease changes across the age spectrum. The research is published in the August 10, 2011, online issue of Neurology®, the medical journal of the American Academy of Neurology.

"Those who are 85 and older make up the fastest growing population in the world," said study author Mark Bondi, Ph.D., with the University of California San Diego School of Medicine and VA San Diego Healthcare System. "Our study shows how age has a dramatic effect on the profile of brain atrophy and cognitive changes evident in Alzheimer's disease."

The study involved 105 people with Alzheimer's disease and 125 people who were free of dementia and recruited through the Alzheimer's Disease Neuroimaging Initiative. Participants were grouped into those who were between the ages of 60 and 75 and those age 80 years and older. All were given tests that measured language, attention and speed of processing information, executive function, and immediate and delayed ability to recall information.

Participants also underwent brain scans to measure the thickness of the outermost tissue layers in the cerebrum of the brain.

Even though the two groups had similar levels of overall cognitive impairment, researchers found that the pattern of changes associated with Alzheimer's disease appeared to be less noticeable in people over the age of 80 (very-old) compared to those between the ages of 69 and 75 (young-old). When compared to their healthy counterparts, executive function, immediate memory and attention/processing speed were less abnormal in those considered very old compared to those considered young-old. The very-old also showed less severe thinning of portions of cerebral cortex and the overall cerebrum than the young-old, as compared to their healthy counterparts. This is in part because these brain areas decrease in thickness due to age, so there are fewer differences between the healthy very-old brain and the very-old brain with Alzheimer's disease, Bondi said.

The study was supported by National Institute on Aging, the National Institutes of Health, the National Institute of Biomedical Imaging and Bioengineering, Abbott, AstraZeneca AB, Bayer Schering Pharma AG, Bristol-Myers Squibb, Eisai Global Clinical Development, Elan Corporation, Genentech, GE Healthcare, GlaxoSmithKline, Innogenetics, Johnson and Johnson, Eli Lilly and Co., Medpace, Inc., Merck and Co., Inc., Novartis AG, Pfizer Inc., F. Hoffman-La Roche, Schering-Plough, Synarc, Inc., Wyeth, the Alzheimer's Association and Alzheimer's Drug Discovery Foundation with participation from the U.S. Food and Drug Administration, the Northern California Institute for Research and Education and the Dana Foundation.