The findings showed that each one of several lifestyle factors - a healthy body mass index, physical activity and a Mediterranean diet - were linked to lower levels of plaques and tangles on the brain scans. Plaque, deposits of a toxic protein called beta-amyloid in the spaces between nerve cells in the brain; and tangles, knotted threads of the tau protein found within brain cells, are considered the key indicators of Alzheimer's.
The Mediterranean diet is rich in fruits, vegetables, legumes, cereals and fish and low in meat and dairy, and characterised by a high ratio of monounsaturated to saturated fats, and mild to moderate alcohol consumption.
Earlier studies have linked a healthy lifestyle to delays in the onset of Alzheimer's disease.
However, the new study is the first to demonstrate how lifestyle factors directly influence abnormal proteins in people with subtle memory loss who have not yet been diagnosed with dementia, the researchers said. "The study reinforces the importance of living a healthy life to prevent Alzheimer's, even before the development of clinically significant dementia," said lead author David Merrill, Psychiatrist at the University of California, Los Angeles.
Healthy lifestyle factors have also been shown to be related to reduced shrinking of the brain and lower rates of atrophy in people with Alzheimer's.
Older age is the leading non-modifiable risk factor for Alzheimer's disease.
"The fact that we could detect this influence of lifestyle at a molecular level before the beginning of serious memory problems surprised us," Merrill added.
In the study, 44 adults ranging in age from 40 to 85 with mild memory changes but no dementia underwent an experimental type of positron emission tomography (PET) scan to measure the level of plaque and tangles in the brain.
Researchers also collected information on participants' body mass index, levels of physical activity, diet and other lifestyle factors.
"The work lends key insight not only into the ability of patients to prevent Alzheimer's disease, but also physicians' ability to detect and image these changes," Merrill noted in the paper appearing in the American Journal of Geriatric Psychiatry.