In a new study, researchers found that brain changes linked to Alzheimer’s disease can appear 3 to 10 years—some even more than 30 years—before the disease’s symptoms appear.
They suggest that it may be possible to use brain imaging and spinal fluid analysis to assess the risk of Alzheimer’s disease at least 10 years before the most common symptoms.
The research was conducted by a team from Johns Hopkins University.
In the study, the team examined medical records collected from 290 people age 40 and older who were at risk for Alzheimer’s disease.
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 team also collected cerebrospinal fluid and 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.
All 290 participants were cognitively normal when the study began, so the scientists were able to track various biological and clinical features linked to Alzheimer’s disease years before the appearance of symptoms.
By the time of their last appointment with the team, 209 participants remained cognitively normal, and 81 were diagnosed with mild cognitive impairment or dementia due to Alzheimer’s disease.
In these 81 people, the team found 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 in cerebrospinal fluid an average of 34.4 years (for total Tau) and 13 years (for a modified version called p-tau) before the beginning of Alzheimer’s symptoms.
Tau is a major biomarker of Alzheimer’s disease.
The team cautions that brain changes can vary widely in people. Their findings reflect an average level of such changes in a small group of research subjects.
The work may lead to a new test to determine a person’s relative risk for Alzheimer’s disease and to guide treatments.
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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