When protein beta-amyloid in the brain that is linked to Alzheimer's disease is at high levels, it may affect brain performance even in healthy adults, according to a study published in the February 1, 2012, online issue of Neurology®, the medical journal of the American Academy of Neurology.
"In our study, we observed that even in adults with apparently good cognitive health, increasing amounts of beta-amyloid in the brain are related to subtle changes in memory and mental function," said study author Denise C. Park, PhD, of the Center for Vital Longevity at the University of Texas at Dallas.
For the study, 137 people between the ages of 30 and 89 who were highly educated and free of dementia underwent brain scans. Participants were also tested for the APOE gene, which has been linked to a higher risk of Alzheimer's disease.
The study found that the amount of beta-amyloid in people's brains increased with age and that about 20 percent of adults age 60 and older had significantly elevated levels of beta-amyloid. Higher amounts of beta-amyloid detected on brain scans were linked with lower test scores related to working memory, reasoning and speed of processing information.
In the group with higher levels of beta-amyloid, 38 percent of people had the Alzheimer's risk allele of the APOE gene compared to 15 percent of people who did not have higher levels of beta-amyloid.
"A key question for future research is whether some adults with high levels of beta-amyloid will maintain good mental function for a long period of time and whether higher beta-amyloid deposits in healthy adults always predetermines cognitive decline," said Park.