Identifying Alzheimer’s in Adulthood

A study published in the journal Neurology suggests that risk factors for sporadic (idiopathic) Alzheimer’s disease can be evaluated in early adulthood. Unlike Familial Alzheimer’s Disease (FAD), which is caused by three genetic mutations, tests did not previously exist for sporadic Alzheimer’s because it is caused by genetic and environmental factors. The genetic risks for sporadic Alzheimer’s may make a person more susceptible to cognitive decline and a diagnosis of Alzheimer’s or dementia. Sporadic Alzheimer’s currently accounts for 95% of all Alzheimer’s cases, making this study a major breakthrough.

These genetic risk factors impact the size of the hippocampus, a brain region synonymous with “memory storage”.  One of the tests that the study found may be useful in identifying Alzheimer’s is to examine the person’s hippocampus. However, Elizabeth Mormino, researcher at Massachusetts General Hospital and lead author of the study, admitted that they cannot guarantee that those participants with smaller hippocampal volumes will develop Alzheimer’s, as that sort of extended follow-up had not been done.

Based off of this idea, the study used a Magnetic Resonance Imaging (MRI) machine to look at the hippocampi of 166 people with dementia and 1026 people who were cognitively healthy. Participants were, on average, 75 years old and also underwent a DNA test for specific gene variants associated with the development of Alzheimer’s disease, which is known as a polygenic risk score.

The research team found a small association between the polygenic risk score and hippocampal volume in the group of older adults. They also calculated the polygenic risk score and hippocampal volume for 1322 healthy adults between the ages of 18 and 35, and found a small association in this group as well. Although the association is small (polygenic risk score accounted for .2% of the variance in hippocampal volume), this link is evidence that Alzheimer’s risk may be identifiable decades before clinical symptoms are present.

Even though this association is not a guarantee that an individual will develop Alzheimer’s disease, Mormino notes that these preliminary findings help to inform their understanding of the underlying mechanisms of the disease. This study is another step on the path to a cure.

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