Research on Alzheimer’s disease has long been focused on the elderly, particularly on the proteins that build up in the brain of people as they age. A new study published July 13 in the journal Neurology says changes in the brain associated with the illness can be seen as early as childhood in some people who have a heightened genetic risk for Alzheimer’s.
The study looked at a database of 1,187 healthy children and young adults aged 3 to 20 years. Brain imaging and cognitive testing data were available on all participants. All had been tested for variants of the gene associated with Alzheimer’s, the apolipoprotein E (APOE).
Everyone has two copies of the APOE gene, inheriting one from each parent. The study researchers found that some people have a variation of at least one copy of the gene, called the e4 variant, which is the version most associated with a heightened risk of Alzheimer’s. In these people the size of the brain region known as the hippocampus was significantly smaller than in the other study participants. The hippocampus is the part of the brain responsible for memory formation. Children with two copies of the e4 variants performed particularly poorly on memory tests.
People with at least one copy of the e4 variant also had smaller regions of the cerebral cortex that are involved in tasks such as decision-making and object recognition. Linda Chang of the University of Hawaii in Manoa and the lead author for the study said these kinds of brain structure changes are often “thought to be a result of Alzheimer’s disease.” However, they “might be present already in childhood.”
Comparing test scores and genetic traits provided inconsistent results. For example, those with the lowest scores on attention tests were from children who had one e4 and one e2 variant, which is a trait that is thought to protect against Alzheimer’s. However, the researchers say more work is needed to test children who carry e2, which is the least-common version of the APOE gene.
The results “do not have immediate implications” clinically, according to developmental cognitive neuroscientist Rebecca Knickmeyer, who was not involved in the study. However, they do add to the growing body of knowledge that suggests that Alzheimer’s is a developmental condition that may start early.