Alzheimer's gene may shrink brain regions in childhood: study

Washington: A gene associated with Alzheimer's disease may shrink brain regions and reduce thinking skills as early as childhood, a finding that may help researchers develop ways to prevent the disease from occurring, according to a new study.

Prior studies showed that people with the epsilon (e) 4 mvariant of the apolipoprotein-E gene are more likely to develop Alzheimer's disease than people with the other two variants of the gene, e2 and e3, researchers said.

"Studying these genes in young children may ultimately give us early indications of who may be at risk for dementia in the future and possibly even help us develop ways to prevent the disease from occurring or to delay the start of the disease," said Linda Chang from University of Hawaii in the US.

For the study, 1,187 children ages three to 20 years had genetic tests and brain scans and took tests of thinking and memory skills. The children had no brain disorders or other problems that would affect their brain development, such as prenatal drug exposure.

Each person receives one copy of the gene (e2, e3 or e4)  from each parent, so there are six possible gene variants: e2e2, e3e3, e4e4, e2e3, e2e4 and e3e4.

The study found that children with any form of the e4 gene had differences in their brain development compared to children with e2 and e3 forms of the gene. The differences were seen in areas of the brain that are often affected by Alzheimer's disease, researchers said.

In children with the e2e4 genotype, the size of the hippocampus, a brain region that plays a role in memory, was approximately 5 per cent smaller than the hippocampi in the children with the most common genotype (e3e3), they said.

Children younger than 8 and with the e4e4 genotype typically had lower measures on a brain scan that shows the structural integrity of the hippocampus, researchers said.

"These findings mirror the smaller volumes and steeper decline of the hippocampus volume in the elderly who have the e4 gene," said Chang.

In addition, some of the children with e4e4 or e4e2 genotype also had lower scores on some of the tests of memory and thinking skills, researchers said.

Specifically, the youngest e4e4 children had up to 50 per cent lower scores on tests of executive function and working memory, while some of the youngest e2e4 children had up to 50 per cent lower scores on tests of attention, they said.

However, children older than 8 with these two genotypes had similar and normal test scores compared to the other children.

The findings were published in the journal Neurology.