Genetic Changes Contribute to the Aging Brain

Hippocampal atrophy is a recognized biological marker of Alzheimer's disease.  An international team of researchers reports that genetic variabilities are linked to the shrinkage of the hippocampus. The team assessed genomic data and MRI scans over 9,000 people, ages 56 and 84 years.  The participants (both subjects presenting dementia and healthy subjects) were extracted from eight cohort studies in Europe and in North America. The researchers first identified 46 differences in the DNA sequences of the participants, thought to be related to a reduction in the volume of the hippocampus. Eighteen mutations located in different areas of chromosome 12 were found to be strongly linked to shrinkage of the hippocampus. The other links included a mutation on chromosome 2. Then a final mutation on chromosome 9 was also found to be involved in the hippocampal shrinkage in a third and younger sample. These results indicate that "as yet unidentified factors" trigger mutations in precise areas of the genome, causing the reduction of the hippocampal volume.