Washington, Apr 16 (IANS): A quartet of genes, identified in the first ever genetic analysis of more than 9,000 people, may speed shrinkage of a brain region involved in making new memories, says recent research.

The brain area, known as the hippocampus, normally shrinks with age, but if the process speeds up, it could increase vulnerability to Alzheimer's disease, say two new studies.

The second study, also conducted by a team of 80 scientists from eight countries, co-led by University of California-Davis neurology professor Charles DeCarli, identified two genes tied with a fully developed intracranial (brain) volume, the journal Nature Genetics reported.

The gene variants identified in the first study do not cause Alzheimer's, but they may rob the hippocampus of a kind of "reserve" against the disease, which is known to cause cell destruction and dramatic shrinkage of this key brain site. The result is severe loss of memory and cognitive ability, said a university statement.

Looked at another way, if a person with one of these variants did get Alzheimer's, the disease would attack an already compromised hippocampus and so would lead to a more severe condition at a younger age than otherwise, the research suggested.

"This is definitely a case of 'bigger is better'," said DeCarli. "We already know that Alzheimer's disease causes much of its damage by shrinking hippocampus volume. If someone loses a greater-than-average amount of volume due to the gene variants we've identified, the hippocampus is more vulnerable to Alzheimer's."