"These results are exciting because if we can identify the genes that are responsible for memory, they may lead us to identifying more of the genes that contribute to Alzheimer's disease," said study authors Joseph H. Lee, DrPH, and Richard Mayeux, MD, MSc, of the Taub Institute at Columbia University in New York, N.Y.
The researchers studied 1,036 people from 266 families, mainly in the Dominican Republic and Puerto Rico. Most of the families had more than one person living with Alzheimer's disease in the extended family, including siblings, aunts, uncles, cousins and others.
All of the study participants were tested for memory, attention, abstract reasoning, language and visual-spatial ability. The results were then analyzed to determine how much of the individual's ability in those areas was due to genetics. Memory performance was found to be strongly influenced by genetics.
"We found that about half of the variation in memory performance among individuals is due to genetics," Mayeux said. "The other half is due to environmental factors such as education. Considering that even with dominant traits, such as a genetic mutation that leads to early onset Alzheimer's, the genetic influence actually amounts to about 80 percent, this shows that memory performance has a strong genetic influence."
The influence of genetics was not as strong in the areas of attention, abstract reasoning, language and visual-spatial ability. The result with memory performance was found even after excluding the memory scores for the people with Alzheimer's.