The finding, published in the early online addition of Annals of Neurology, comes from a study of 2,258 older adults in New York. At the study's start, participants were in their 70s, on average, and none had dementia. Alzheimer's disease is the most common form of dementia in seniors.
Participants took a 61-item survey about the foods they typically ate. They also took a battery of tests every 1.5 years for four years to screen for Alzheimer's. Those tests covered mental skills including memory, language, and reasoning.
Participants weren't asked to change their eating habits. During the study, the group had 262 cases of Alzheimer's, with fewer cases seen in participants on Mediterranean-style diets.
Lower Rates of Alzheimer's Disease
"The main finding of the study is that higher adherence to a Mediterranean diet type of food consumption is associated with decreased risk for developing Alzheimer's disease," neurologist Nikoloas Scarmeas, M.D., tells WebMD.
Scarmeas, who worked on the study, is an assistant professor of neurology at New York's Columbia University Medical Center.
Based on participants' food surveys, Scarmeas and colleagues gave each participant a score for adherence to a Mediterranean-style diet.
Scores ranged from 0-9, with higher scores showing greater adherence to a Mediterranean diet.
Compared with those with the lowest scores, those with middle scores were 15 percent less likely to have been found to have developed Alzheimer's disease, and those with the highest scores were 40 percent less likely to have been found to have Alzheimer's disease.
Adjusting for age, ethnicity, education, genetic factors linked to Alzheimer's disease, and caloric intake didn't change the results.
What Did They Eat?
The Mediterranean diet included high intake of certain foods:
The Mediterranean diet also includes moderate amounts of fish of all types, low intake of meat and poultry, low-to-moderate amounts of dairy products, and a moderate amount of alcohol (usually wine served at meals).