21 Apr Effect of Mediterranean Diet on Cognitive Function in Patients with Age-Related Eye Disease

MedicalResearch.com Interview with:

Dr. Chew

Emily Y. Chew, M.D.
Director of the Division of Epidemiology and Clinical Applications
Deputy Clinical Director at the National Eye Institute (NEI),
National Institutes of Health 

MedicalResearch.com: What is the background for this study?

Response: Dementia is a common disorder that was estimated to have a worldwide prevalence of 44 million in 2016 and is projected to hit 115 million by 2050. Many phase 3 trials of various therapies have failed and we have no treatment currently available for the prevention or reduction of the course of dementia. A slow neurocognitive decline throughout life is part of the normal process of aging. However, there is a subset of individuals who may have accelerated aging and is at high risk of development dementia. If the course of such accelerated decline could be altered in any way, it would be important to evaluate. The role of diet with biologic aging has been studied and diet has been also found to be associated with age-related conditions linked to dementia, including cardiovascular disease and diabetes.

We were interested in the cognitive function of our participants who had another neurodegenerative disease, age-related macular degeneration (AMD). We had conducted two randomized controlled clinical trials designed to evaluate the role of oral supplements for the treatment of AMD. We also studied cognitive function in both clinical trials of nearly 8,000 participants who were followed for 10 years. We also evaluated the dietary habits of the participants with food frequency questionnaires (FFQ) at baseline. Cognitive function testing was conducted in the first study, the Age-Related Eye Disease Study (AREDS) near the end of the clinical trial while the AREDS2, the second study, evaluated cognitive function testing at baseline and every 2 years until year 6. AREDS study evaluated cognitive function with in-clinic study visits while AREDS2 was conducted using telephone interviews.

Our aim was to determine whether closer adherence to the alternative Mediterranean diet (aMED) was associated with impaired cognitive function these two studies. We were interested in the particular components of the Mediterranean diet that may be important. We also evaluated the interaction of genetics with the diet.   

MedicalResearch.com: What are the main findings?

Response: Mediterranean diet adherence was associated with decreased risk of cognitive impairment. There was a dose response relationship in that the higher the adherence, the better the beneficial effect. The results were consistent between the two clinical trials of persons who did not have cognitive impairment at the baseline of the study but did have varying degrees of severity of AMD. The strength of this relationship of diet with cognitive function was fairly large with 40 to 50 % reduction.

Higher fish consumption was associated with decreased risk of cognitive impairment and slower cognitive decline. Fish may be the component that drives the effects of the Mediterranean diet on cognitive function to a certain extent.   But in general, the Mediterranean diet with all its components may play a very important role in cognitive function.

MedicalResearch.com: What role did the ApoE gene have on the results?

Response: Although APOE risk haplotypes were significantly associated with faster decline in cognitive impairment scores (p<0.0001) in general, APOE status did not influence the association of the Mediterranean diet with decreased risk of cognitive impairment and nor did it have an influence on the association of fish consumption with decreased risk of cognitive impairment and slower cognitive decline. 

MedicalResearch.com: What should readers take away from your report?

Response: It is important to consider possible modification with your diet. These are not the results of a randomized trial but the data are quite compelling. And other studies have supported this theory that you are what you eat. Eating fish twice a week has beneficial effects and having a Mediterranean diet has been demonstrated to reduce the risk of heart disease and impairment in cognition.

MedicalResearch.com: What recommendations do you have for future research as a result of this study?

Response:  This is a study of association so it would be important to have randomized controlled clinical trials to test the effect of a Mediterranean Diet on cognitive function. A randomized trial (PREDIMED) conducted in Spain with comparisons between Mediterranean diet vs. low fat diet found that participants randomized to a Mediterranean diet had higher cognitive function scores after 6.5 years than those randomized to a low-fat control diet. The NIH is also supporting the Mediterranean-DASH Diet Intervention for Neurodegenerative Delay (MIND) Study. This is a Phase III randomized controlled trial designed to test the effects of a 3-year intervention of a hybrid of the Mediterranean and DASH diets, called MIND, on cognitive decline among 600 individuals 65+ years without cognitive impairment who are overweight and have suboptimal diets, as described the clinicaltrials.gov. That would be the gold standard for establishing a potential treatment for cognitive impairment. This study is done in persons who are high risk of developing cognitive decline. 

I have no financial disclosures or other relevant disclosures to report.

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Last Updated on April 21, 2020 by Marie Benz MD FAAD