Diet Associated With Lower Risk of Cognitive Impairment

April 16, 2020

Consumption of whole fruits, vegetables, whole grains, nuts, legumes, fish and olive oil, as well as reduced consumption of red meat and alcohol was observed to assist in preserving cognitive function.

Tiarnan D. Keenan, MD, PhD

Analysis of data from the Age-Related Eye Disease Study (AREDS) and AREDS2, published in Alzheimer’s and Dementia by researchers at the National Eye Institute (NEI), suggest dietary factors can play a role in slowing cognitive decline. More specifically, diets that include high consumption of vegetables, whole grains, fish, and olive oil correlate with higher cognitive function.1

The risk of cognitive impairment was found in participants with the greatest adherence to the alternative Mediterranean diet (aMED). The odds ratio (OR) for cognitive impairment in patients with the greatest adherence to aMED was 0.36 (P = .0001) for a Modified Mini-Mental State Examination (3MS) score <80, 0.56 for composite score (P = .001), as well as 0.56 for Telephone Interview Cognitive Status-Modified (TICS-M) score <30 and 0.48 for composite score (P <.0001 for both) compared with those in the lowest adherence tertile.2 The diet consisted of 9 components, including consumption of whole fruits, vegetables, whole grains, nuts, legumes, fish, and olive oil, in addition to reduced consumption of red meat and alcohol.

The regression estimates in aMED tertile 3—participants with the greatest adherence—were +1.3 (P <.0001) versus +1.0 (P <.0001) in the lowest adherence group. Although the numerical differences in cognitive function scores between participants with the highest versus lowest adherence to aMED were relatively small, the belief is that over a large population size, the effect clearly shows a correlation between cognition, neural health and diet, according to the investigators, including Tiarnán D. Keenan, MD, PhD, staff clinician, Division of Epidemiology and Clinical Applications, NEI.

In AREDS2, the rate of cognitive decline over 5 to 10 years was not significantly different by the Mediterraneon diet (aMED), but was signifcantly slower (P = .019) with higher fish intake.

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“Closer adherence to a Mediterranean diet was associated with lower risk of cognitive impairment but not cognitive decline,” Keenan et al. wrote. “However, higher fish consumption was significantly associated with slower cognitive decline. APOE genotype did not influence these relationships.”

AREDS (NCT00594672) and AREDS2 (NCT00345176) were 2 prospective studies that examined the effect of vitamins on age-related macular degeneration (AMD) around 4000 participants. AREDS contained patients with and without AMD while AREDS2 contained only those with AMD. Additionally, AREDS aimed to determine the clinical course and prognosis of AMD and cataracts, as well as possible risk factors with the development of AMD and cataracts.

Each patient was assessed on diet at the start of both studies. Cognitive function at 5 years was observed in AREDS, while cognitive function was assessed at baseline and again 2, 4 and 10 years later in AREDS2.

Each patient was evaluated on cognitive impairment from results on 3MS. Average consumption of each aMED component was answered on a questionnaire by patients and evaluated by researchers.

In addition to a lower risk of cognitive impairment in participants with the greatest adherence to aMED, researchers also found that participants with the APOE gene, on average, had lower cognitive function scores and greater decline than those without the gene (P <.0001).

Linked with a higher risk for Alzheimer disease (AD), researchers noted the benefits of close adherence to a Mediterranean diet were similar for people with and without the APOE gene (interaction P = .80 for TICS-M; interaction P = .51 for composite). These results indicated that there is no correlation between the effects of diet on cognition and risk of AD.

“These findings may help inform evidence-based dietary recommendations to maximize cognitive reserve against dementia,” Keenan and colleagues concluded. “Using the same data, future analyses will evaluate individual nutrients that may be responsible for the inverse association between the diet and cognitive function found in these 2 studies.”

REFERENCES

1. Diet may help preserve cognitive function [news release]. Bethesda, MD: National Institutes of Health; Published April 14, 2020. Accessed April 15, 2020. nih.gov/news-events/news-releases/diet-may-help-preserve-cognitive-function

2. Keenan, TD, Agron E, Mares JA, et al. Adherence to a Mediterranean diet and cognitive function in the Age-Related Eye Disease Studies 1 & Alzheimers Dement. Published online April 13, 2020. doi: 10.1002/alz.12077