Because preventive therapies for Alzheimer's will likely be more effective the earlier they are begun, the ability to identify people at high risk of the disease many years before symptoms are expressed will be important for its eventual prevention, the researchers say.
Karen Gosche, PhD, and her colleagues found that shrinkage of the hippocampus, a region of the brain showing some of the first signs of Alzheimer's disease, occurs very early in the disease process -- long before the illness spreads to the cerebral cortex and results in cognitive and memory impairment. Dr. Gosche, president of NeuroImaging Research, Inc. in Alachua, FL, conducted the study while she was a doctoral candidate in Aging Studies at USF.
"The findings suggest that MRI measures of the hippocampus may help us to identify individuals who will develop Alzheimer's disease decades in the future," said James Mortimer, PhD, director of the USF Institute on Aging and one of the co-authors of the study.
Postmortem MRI brain scans of 56 participants of the Nun Study were analyzed. Smaller volumes of the hippocampus seen on the scans could correctly identify older Catholic sisters who were cognitively normal before they died but fulfilled pathological criteria for fully developed Alzheimer's disease at autopsy. In addition, the smaller hippocampal volumes were an indicator of milder pathological changes -- the accumulation of senile plaques and neurofibrillary tangles -- believed to occur decades before the appearance of symptoms such as memory loss.
The volume of the hippocampus was measured with a new computer program that reduces the time required to compute this volume from more than a half hour to a couple of minutes. Previous methods required tracing of this structure by hand, which restricted its application to research studies.
The findings suggest hippocampal volume could be valuable in predicting who is likely to develop Alzheimer's disease, but the researchers emphasize that applying the technique to MRI brain scans of living people will require further study.
The Nun Study, begun in 1992, is a study of 678 Catholic sisters, initially 75 to 102 years of age, who are evaluated annually and who have agreed to brain donation at the time of death. It is one of the first large autopsy studies to include normal as well as demented participants.
The Nun Study is directed by David Snowdon, PhD, of the University of Kentucky. Dr. Snowdon is a co-author of the current article along with William Markesbery, MD, director of the Sanders-Brown Center on Aging, and Charles Smith, MD, of the Department of Neurology at the University of Kentucky.