In a new study, researchers found that biological and anatomical brain changes linked to Alzheimer’s disease that occur three to 10 years, some even more than 30 years, before the disease’s first recognizable symptoms appear.
The finding shows it may be possible to use brain imaging to assess the risk of Alzheimer’s disease at least 10 years or more before the most common symptoms.
The research was conducted by scientists at Johns Hopkins.
In the study, the team examined medical records collected from 290 people age 40 and older.
Most of the 290 people had at least one first degree relative with dementia of the Alzheimer’s disease type, putting them at higher than usual risk.
The scientists performed MRI brain scans of study participants every two years between 1995 and 2005.
They also did five standard tests of memory, learning, reading, and attention annually from 1995 to 2013.
At the end of the study period, 209 participants remained cognitively normal, and 81 were diagnosed with mild cognitive impairment or dementia due to Alzheimer’s disease.
The team found in the 81 people who developed cognitive problems or dementia, there were subtle changes in cognitive test scores 11 to 15 years before the onset of clear cognitive impairment.
They also found increases in the rate of change of a protein called Tau, which has long been considered a marker of Alzheimer’s disease in cerebrospinal fluid an average of 34.4 years and 13 years before the beginning of cognitive impairment.
In addition, the scientists detected slight decreases in the size of the medial temporal lobe, an area of the brain responsible for memory, between 3 and 9 years before cognitive impairment was apparent.
The team cautions that brain changes vary widely in people and that their research findings reflect an average level of such changes in a small group of patients.
But the work could lead eventually to a test to determine an individual’s relative risk for Alzheimer’s disease and to guide the use of treatments when and if they are developed.
One author of the study is Laurent Younes, Ph.D., professor and chair of the Department of Applied Mathematics and Statistics at The Johns Hopkins University
The study is published in Frontiers in Aging Neuroscience.
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