Maintaining a healthy lifestyle by staying mentally sharp and physically active in middle age can only delay symptoms of Alzheimer's disease, a recent study claims.

A research team headed by Prashanthi Vemuri at Mayo Clinic in Rochester, Minn., recruited 393 participants from the Mayo Clinic Study of Aging who were between the ages of 70 and 89. None of the participants were diagnosed with dementia, but 53 had signs of slight cognitive decline. Some of the participants carried the gene that has been linked to Alzheimer's, called APOE4. Experts have estimated that about 20 percent of the population has the APOE4 gene.

The team divided the sample into two groups based on whether or not the participants had at least 14 years of education. All of the participants underwent MRI and PET scans to check for signs of dementia, which would manifest in the form of amyloid protein plaques, and filled out questionnaires about their mental and physical activity levels.

"There is substantial evidence that these activities help to delay the onset of memory and thinking problems," Vemuri said in a news release.

The researchers found that overall, physical and mental activity levels, as well as education levels, had no effects on the amount of amyloid plaques that had built up in the brain. When the team factored in the APOE4 gene, they found that higher education and mental activity later on in life were linked to a reduced amount of amyloid plaque buildup. Despite these findings, the researchers noted that education and mental activity levels cannot prevent the onset of Alzheimer's.

"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," Vemuri said. "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."

The researchers could not determine why or how education and mental activity delayed symptoms of dementia and stressed the importance of conducting more studies to understand how higher education can benefit the brain.

Anja Soldan at Johns Hopkins University in Baltimore, who was not involved with the research, advised people to remain mentally stimulated regardless of the study's findings.

"Find something that you enjoy, and try exposing yourself to new things that are challenging," Soldan told Reuters Health.

The study's findings were published in the Feb. 24 issue of the journal Neurology.