Experts have often suggested that diet may play a role in the development of Alzheimer's disease but epidemiological data on diet and Alzheimer's is scarce and often contradictory and while individual foods and nutrients have been previously studied, general dietary patterns have not.
In order to address this lack of clinical data, researchers at Columbia University Medical Center, designed a prospective community-based study of 2,258 non-demented people in New York City.
The study was funded by the National Institute on Aging and the subjects drawn from the Washington Heights-Inwood Columbia Aging project.
The researchers led by Dr. Nikolaos Scarmeas gathered medical and neurological history for each of the participants and did a standardized physical and neurological exam, along with an in-person interview, to assess health and neuropsychological function.
The information was then used to diagnose a presence or absence of dementia.
The participants were reassessed approximately every 18 months for an average duration of 4 years.
The researchers also collected dietary data from each subject using a semi-quantitative food frequency questionnaire.
They determined a Mediterranean Diet score (0-9) based on a previously described method.
During the course of the study, 262 members of the study population were diagnosed with Alzheimer's disease.
The researchers say those who adhered to the Mediterranean diet had a significantly lower risk of developing Alzheimer's disease.
This benefit remained just as significant even after adjustments were made for factors such as age, gender, ethnicity, education, caloric intake, BMI, smoking and comorbid conditions.
The more people kept to a Mediterranean diet, the less likely they were to develop Alzheimer's and for each additional point on the Mediterranean diet scale, the risk of Alzheimer's dropped by almost 10%.
The study adds to the growing body of evidence that diet and lifestyle are very important risk factors for Alzheimer's disease.
The study is published in the Annals of Neurology.