Changes in the genes we carry can have a big impact on our risk of getting certain diseases. A variant of the apolipoprotein (APOE) gene is the most common genetic factor linked to Alzheimer’s disease development that we know of. There are three (or more) major classes of APOE gene variants, referred to as APOE2, APOE3, and APOE4. Now scientists have found that people who carry the APOE4 gene are not only at risk of developing Alzheimer’s disease. They may also experience problems with attention and memory, even when there are no obvious signs of illness. The findings have been outlined in Scientific Reports.
In this study, 60 volunteers aged 40 to 61, who had different combinations of the APOE4 gene and normal hearing had to listen to 92 audio clips. One group of people carried APOE4 genes, another carried a combination of APOE4 and APOE3 genes, and the last group had APOE3 genes. They all fell in the normal range on their cognitive tests.
While listening to the audio clips, the participants noted whether the sound they heard was in their left, right, or in both ears. Incorrect assessments were replayed. Then they got a one hour break and repeated the listening, but also had to acknowledge another sound at the end of the clips, which they were told about. They pressed a button when they heard the new sound, and each clip was played twice - first without the new tone, then with.
All of the study participants could learn the new information and remember which ears heard the clip. But, the additional sound at the end was harder for the people with APOE4 to identify. The APOE4 carriers seemed to have a tougher time remembering information they’d just learned, and maybe greater difficulty accessing knowledge.
This work could lead to the development of new ways to detect individuals at risk.
"For some reason, people with the APOE4 gene were not able to take advantage of information they learned earlier, such as the expected location of the clip, to boost their performance," explained senior study author Dr. Claude Alain, a senior author on the paper and senior scientist at Baycrest Centre for Geriatric Care. "This study shows we have a test that is sensitive to capture problems or challenges faced by individuals with this gene, before their deficits are observed on a standard neuropsychological assessment."
"The research could lead to more sensitive methods of detecting Alzheimer's disease in its very earliest stages, the time at which treatments are most likely to be effective," said senior author Dr. Chris Butler, an associate professor in clinical neurosciences at the University of Oxford. "I was delighted to carry out this work with researchers from Baycrest."
Learn more about how the APOE4 plays a role in Alzheimer’s from the video above by Cell Press.