Newswise, July 29, 2016– A gene associated with Alzheimer’s
disease and recovery after brain injury may show its effects on the brain and
thinking skills as early as childhood, according to a study published in the
July 13, 2016, online issue of Neurology®, the medical journal of the
American Academy of Neurology.
Prior studies showed that people with the epsilon(ε)4 variant
of the apolipoprotein-E gene are more likely to develop Alzheimer’s disease
than people with the other two variants of the gene, ε2 and ε3.
“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 study author Linda Chang, MD, of the University of
Hawaii in Honolulu and a Fellow of the American Academy of Neurology.
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 (ε2, ε3 or ε4) from
each parent, so there are six possible gene variants: ε2ε2, ε3ε3, ε4ε4, ε2ε3,
ε2ε4 and ε3ε4.
The study found that children with any form of the ε4 gene had
differences in their brain development compared to children with ε2 and ε3
forms of the gene. The differences were seen in areas of the brain that are
often affected by Alzheimer’s disease.
In children with the ε2ε4 genotype, the size of the
hippocampus, a brain region that plays a role in memory, was approximately 5
percent smaller than the hippocampi in the children with the most common
genotype (ε3ε3).
Children younger than 8 and with the ε4ε4 genotype typically
had lower measures on a brain scan that shows the structural integrity of the
hippocampus.
“These findings mirror the smaller volumes and steeper decline
of the hippocampus volume in the elderly who have the ε4 gene,” Chang said.
In addition, some of the children with ε4ε4 or ε4ε2 genotype
also had lower scores on some of the tests of memory and thinking skills.
Specifically, the youngest ε4ε4 children had up to 50 percent
lower scores on tests of executive function and working memory, while some of
the youngest ε2ε4 children had up to 50 percent lower scores on tests of
attention.
However, children older than 8 with these two genotypes had
similar and normal test scores compared to the other children.
Limitations of the study include that it was cross-sectional,
meaning that the information is from one point in time for each child, and that
some of the rarer gene variants, such as ε4ε4 and ε2ε4, and age groups did not
include many children.
The study was supported by the National Institutes of Health,
including the National Institute on Drug Abuse and the Eunice Kennedy Shriver
National Institute on Child Health and Human Development.
The American Academy of Neurology, the world’s largest
association of 30,000 neurologists and neuroscience professionals, is dedicated
to promoting the highest quality patient-centered neurologic care.
A neurologist is a doctor with specialized training in
diagnosing, treating and managing disorders of the brain and nervous system
such as Alzheimer’s disease, stroke, migraine, multiple sclerosis, brain
injury, Parkinson’s disease and epilepsy.
For more information about the American Academy of Neurology,
visit http://www.aan.com or
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