Alzheimer's gene affects brain development in children

A gene variant linked to increased risk of Alzheimer's disease may affect memory and thinking skills in children, a study has found.

There are three variants of the apolipoprotein-E (APOE) gene – ε2, ε3, and ε4 – and people with ε4 are known to have an increased risk of developing Alzheimer's disease. The researchers found that the same ε4 variant also causes differences in children's brains in regions often associated with Alzheimer's.

'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 Professor Linda Chang, who led the research.

Researchers at the University of Hawaii studied 1187 children between the ages of three and 20, giving them brain scans, genetic tests and assessments of their memory and thinking. They evaluated these results against the APOE genotypes. As a copy of APOE is inherited from each parent, there are six possible combinations.

Children with any form of the ε4 genotype had differences in terms of their brain development when compared with children who had the other variants. For example, the hippocampus – a brain structure that plays a role in memory and is affected in the early stages of Alzheimer's disease – was about five percent smaller in children with the ε4ε2 genotype, compared with the more common ε3ε3 genotype.

'These findings mirror the smaller volumes and steeper decline of the hippocampus volume in the elderly who have the ε4 gene,' said Professor Chang.

Moreover, younger children with the ε4►ε4 or ε4ε2 genotype scored lower on some of the memory and thinking tests than the other children. However, these differences disappeared in children over eight years old.

Dr Ian Le Guillou, research officer at the Alzheimer's Society, noted the need for caution in interpreting the results. 'Although this study involved over 1000 children, there were less than 30 in the highest-risk group,' he said. As the APOE ε4 variant is relatively rare, he recommended that these results should be investigated in a larger group.

Furthermore, possessing the ε4 variant does not guarantee development of Alzheimer's disease, which is influenced by many factors. Dr Guillou recommended that further research should monitor how these brain differences progress in children over time.

The research was published in the journal Neurology.