Neurologists Discover Brain Area Shrinking Is Linked to Memory Loss

Age-related memory loss comes in many forms. New research from Harvard suggests that these different forms of dementia, including Alzheimer's disease, may all be linked to shrinkage in one specific region of the brain.

Alzheimer's affects an estimated 5.8 million Americans, according to the Centers for Disease Control and Prevention, and is the most common form of dementia and age-associated memory loss. However, it is not the only form.

Scientists don't yet fully understand the direct causes of the disease in most patients, but we do know that Alzheimer's development is associated with the build-up of abnormal proteins in the brain—such as tau proteins and amyloid plaques—as well as changes in brain structure and function.

The last few years have seen dramatic developments in the field of Alzheimer's research and drug discovery. But distinguishing between Alzheimer's and other forms of cognitive decline is necessary to ensure rapid delivery of effective treatment.

To better understand the molecular underpinnings of these various diseases, Bernard Hanseeuw from Harvard Medical School recruited 128 participants with an average age of 72. The participants were required to have no thinking or memory problems at the start of the study.

Over the seven-year study period, each participant underwent several types of brain scan to measure specific biomarkers of Alzheimer's—such as amyloid plaques and tau protein tangles—as well as the volume of the hippocampus, an area of the brain involved in learning and memory. The participants were also required to undergo annual cognitive evaluations.

Looking at these results, shrinkage in the hippocampus was associated with faster cognitive decline, irrespective of whether the participants were showing biomarkers for early Alzheimer's. Indeed, on its own, shrinkage in the hippocampus accounted for 10 percent of the difference in the extent of cognitive decline between participants.

"These results emphasize that dementia is a complex condition with many underlying causes and suggest that types of dementia other than Alzheimer's disease may contribute to shrinkage in the hippocampus and cognitive decline," Hanseeuw said. "[Our studies] suggest that neurodegenerative diseases other than Alzheimer's are contributing to this decline, and measuring the hippocampus volume may help us evaluate these causes that are currently difficult to measure. This could help us better predict...people's trajectories of cognitive decline."

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