Mediterranean diet and cognitive function in older age

Abstract

Background: Adherence to a Mediterranean diet may help prevent cognitive decline in older age, but studies are limited. We examined the association of adherence to the Mediterranean diet with cognitive function and decline.

Methods: We included 6174 participants, aged 65+ years, from the cognitive substudy of the Women's Health Study. Women provided dietary information in 1998 and completed a cognitive battery 5 years later, followed by two assessments at 2-year intervals. The primary outcomes were composite scores of global cognition and verbal memory. The alternate Mediterranean diet adherence nine-point score was constructed based on intakes of vegetables, fruits, legumes, whole grains, nuts, fish, red and processed meats, moderate alcohol, and the ratio of monounsaturated-to-saturated fats.

Results: After multivariable adjustment, the alternate Mediterranean diet score was not associated with trajectories of repeated cognitive scores (P for score quintiles medians-x-time interaction = 0.26 for global cognition and 0.40 for verbal memory), nor with overall global cognition and verbal memory at older ages, assessed by averaging the three cognitive measures (P trend = 0.63 and 0.44, respectively). Among alternate Mediterranean diet components, a higher monounsaturated-to-saturated fats ratio was associated with more favorable cognitive trajectories (P for ratio quintiles medians-x-time = 0.03 for global cognition and 0.05 for verbal memory). Greater whole grain intake was not associated with cognitive trajectories but was related to better averaged global cognition (P trend = 0.02).

Conclusions: In this large study of older women, we observed no association of the Mediterranean diet with cognitive decline. Relations between individual Mediterranean diet components, particularly whole grains, and cognitive function merit further study.

Figure 1. Alternate Mediterranean diet score and cognitive function over 4 years in the Women’s Health Study

Least square mean global cognitive scores (standardized scores, Figure 1A) and verbal memory scores (standardized scores, Figure 1B) at each time-point are plotted by quintiles of the alternate Mediterranean diet score. They were estimated by analysis of response profiles in a general linear model, adjusting for age at cognitive testing, treatment arm, Caucasian race, high education, high income, energy intake, vigorous exercise, BMI, smoking, diabetes, hypertension, hypercholesterolemia, hormone use and depression. Statistical inference was based on Wald test, examining linear trends across alternate Mediterranean diet score quintiles using a continuous variable in which participants in a given category were assigned the median value. Q1 to Q5 refer to consecutive quintiles of alternate Mediterranean diet score.

Figure 1. Alternate Mediterranean diet score and cognitive function over 4 years in the Women’s Health Study

Least square mean global cognitive scores (standardized scores, Figure 1A) and verbal memory scores (standardized scores, Figure 1B) at each time-point are plotted by quintiles of the alternate Mediterranean diet score. They were estimated by analysis of response profiles in a general linear model, adjusting for age at cognitive testing, treatment arm, Caucasian race, high education, high income, energy intake, vigorous exercise, BMI, smoking, diabetes, hypertension, hypercholesterolemia, hormone use and depression. Statistical inference was based on Wald test, examining linear trends across alternate Mediterranean diet score quintiles using a continuous variable in which participants in a given category were assigned the median value. Q1 to Q5 refer to consecutive quintiles of alternate Mediterranean diet score.

Figure 2. Alternate Mediterranean diet score components and cognitive function over 4 years in the Women’s Health Study

Least square mean global cognitive scores (standardized scores, Figure 2A) and verbal memory scores (standardized scores, Figure 2B) at each time-point are plotted by categories of alternate Mediterranean diet score components. They were estimated by analysis of response profiles in a general linear model, adjusting for age at cognitive testing, treatment arm, Caucasian race, high education, high income, energy intake, vigorous exercise, BMI, smoking, diabetes, hypertension, hypercholesterolemia, hormone use and depression. Fruits, vegetables, legumes, whole grains, nuts, red and processed meats, fish and alcohol intake were all introduced in the same multivariable-adjusted model. The monounsaturated-to-saturated fats ratio was modeled in a separate multivariable-adjusted model, adjusting additionally for alternate Mediterranean diet score food components not providing fats (e.g., fruits, vegetables, legumes, whole grains) and alcohol intake. Statistical inference was based on Wald test, examining linear trends across component categories using a continuous variable in which participants in a given category were assigned the median value. Q1 to Q5 refer to consecutive quintiles of intake of each alternate Mediterranean diet score component; legends correspond to Q1 to Q5 as indicated for fruits intake, unless otherwise noted. Abbreviations: m: month; w: week.

Figure 2. Alternate Mediterranean diet score components and cognitive function over 4 years in the Women’s Health Study

Least square mean global cognitive scores (standardized scores, Figure 2A) and verbal memory scores (standardized scores, Figure 2B) at each time-point are plotted by categories of alternate Mediterranean diet score components. They were estimated by analysis of response profiles in a general linear model, adjusting for age at cognitive testing, treatment arm, Caucasian race, high education, high income, energy intake, vigorous exercise, BMI, smoking, diabetes, hypertension, hypercholesterolemia, hormone use and depression. Fruits, vegetables, legumes, whole grains, nuts, red and processed meats, fish and alcohol intake were all introduced in the same multivariable-adjusted model. The monounsaturated-to-saturated fats ratio was modeled in a separate multivariable-adjusted model, adjusting additionally for alternate Mediterranean diet score food components not providing fats (e.g., fruits, vegetables, legumes, whole grains) and alcohol intake. Statistical inference was based on Wald test, examining linear trends across component categories using a continuous variable in which participants in a given category were assigned the median value. Q1 to Q5 refer to consecutive quintiles of intake of each alternate Mediterranean diet score component; legends correspond to Q1 to Q5 as indicated for fruits intake, unless otherwise noted. Abbreviations: m: month; w: week.