Keeping the brain busy for as long as possible during your younger years and as an adult may be the key to warding off the disorder, which affects memory and personality as well as impairing reasoning.
The study, published in the Neurology journal, monitored 393 dementia-free people over 70 who either carried or didn't carry the gene APoE4, which increases the risk of the disease. They were divided into groups according to their educational history, how much they kept mentally active and whether or not they had the gene. Brain scans took place to identify the biomarkers of the disease too, such as beta-amyloid protein fragments, which are found in Alzheimer's patients.
Those with the gene who had at least 14 years of education and continued to keep their brains active, had lower levels of beta-amyloid than those who carried APoE4 and didn't exercise their minds.
Studying the group as a whole though, it was found education, occupation and mental and physical activity had little effect on the amount of beta-amyloid.
However lead scientist Dr Prashanthi Vemuri of the Mayo Clinic in Minnesota noted that people should continue to stimulate their brains. He added that "substantial evidence" showing such activities prevent age-related memory and thinking problems was evident.
"Recent studies have shown conflicting results about the value of physical and mental activity related to the risk of developing Alzheimer's disease, and we noticed that levels of education differed in those studies," he explained.
"When we looked specifically at the level of lifetime learning, we found that carriers of the APoE4 gene who had higher education and continued to learn through middle age had fewer amyloid deposition on imaging when compared to those who did not continue with intellectual activity in middle age."
Dr Simon Ridley, head of science at the charity Alzheimer's Research UK, also noted that there's more and more evidence mounting up that shows staying mentally active can help your brain in later life.
"As none of the volunteers in the study had symptoms of dementia, it is difficult to make conclusions about the long-term impact of these factors on dementia risk," he said.
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