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Healthy eating and reduced risk of cognitive decline
 
 
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".....first study to investigate the association between diet quality and cognitive impairment in a large multinational cohort of middle-aged and elderly people at high CV risk.....we report that higher diet quality is associated with a reduced risk of cognitive decline. Improved diet quality represents an important potential target for reducing the global burden of cognitive decline.......Foods rich in omega-3 fatty acids, vitamins C and E, folate, and other carotenoids may alter inflammatory pathways via reductions in oxidative stress and lipid per oxidation......Modifying risk factors for covert stroke such as hypertension, independent of diet quality, could also indirectly modify cognitive decline. For example, diets high in fruits and vegetables, which are rich in potassium, may lower blood pressure and reduce the risks of stroke and cognitive decline."
 
Diet is reported to be a potential risk factor for noncommunicable diseases including cardiovascular (CV) disease, Alzheimer disease, and vascular cognitive impairment. Dietary intake may modify the risk of cognitive decline through multiple mechanisms including increased risk of stroke (both overt and covert) and through deficiency of nutrients required for neuronal regeneration (e.g., group B vitamins, and vitamin C).1 However, the association between overall diet quality and cognitive impairment is uncertain. Although some cohort studies did not report any association between a Mediterranean-style diet [http://www.natap.org/2008/AGE/091708_03.htm] and cognitive decline,2-4 others reported that adherence to a Mediterranean diet is associated with slower cognitive decline.5,6 Three recent systematic reviews reported that moderate adherence to a Mediterranean diet is associated with reduced risk of cognitive impairment
 
Mediterranean Diet Improves Health & Mortality.....[http://www.natap.org/2008/AGE/091708_03.htm]...."reduction in overall mortality (9%), mortality from cardiovascular diseases (9%), incidence of or mortality from cancer (6%), and incidence of Parkinson's disease and Alzheimer's disease (13%). These results seem to be clinically relevant for public health, in particular for encouraging a Mediterranean-like dietary pattern for primary prevention of major chronic diseases."......A diet rich in fruits, vegetables, legumes, and cereals, with olive oil as the only source of fat, moderate consumption of red wine especially during meals, and low consumption of red meat has been shown to be beneficial for all cause and cardiovascular mortality, lipid metabolism, blood pressure, and several different disease states such as endothelial dysfunction and overweight.7

 
attached are 2 pdfs, the full study and Supplemental Material which contains "Description of food groups in the food group frequency questionnaire"
 
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Healthy eating and reduced risk of cognitive decline
 
Neurology May 2015
 
Andrew Smyth, MMedSc* Mahshid Dehghan, PhD* Martin O'Donnell, PhD Craig Anderson, MD Koon Teo, MD Peggy Gao, MSc Peter Sleight, DM Gilles Dagenais, MD Jeffrey L. Probstfield, MD Andrew Mente, PhD Salim Yusuf, DPhil On behalf of the ONTARGET and TRANSCEND Investigators
 
From the Population Health Research Institute (A.S., M.D., M.O.D., K.T., P.G., A.M., S.Y.), McMaster University, Hamilton, Canada; Health Research Board Clinical Research Facility (A.S., M.O.D.), National University of Ireland, Galway; The George Institute for Global Health (C.A.), Australia; Nuffield Department of Medicine (P.S.), John Radcliffe Hospital, Oxford, UK; Laval University Heart and Lung Institute (G.D.), Quebec, Canada; and University of Washington (J.L.P.), School of Medicine, Seattle, WA.
 
Abstract
 
Objective: We sought to determine the association of dietary factors and risk of cognitive decline in a population at high risk of cardiovascular disease.
 
Methods: Baseline dietary intake and measures of the Mini-Mental State Examination were recorded in 27,860 men and women who were enrolled in 2 international parallel trials of the ONTARGET (Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial) and TRANSCEND (Telmisartan Randomised Assessment Study in ACE Intolerant Subjects with Cardiovascular Disease) studies. We measured diet quality using the modified Alternative Healthy Eating Index. Cox proportional hazards regression was used to determine the association between diet quality and risk of ≥3-point decline in Mini-Mental State Examination score, and reported as hazard ratio with 95% confidence intervals with adjustment for covariates.
 
Results: During 56 months of follow-up, 4,699 cases of cognitive decline occurred. We observed lower risk of cognitive decline among those in the healthiest dietary quintile of modified Alternative Healthy Eating Index compared with lowest quintile (hazard ratio 0.76, 95% confidence interval 0.66-0.86, Q5 vs Q1). Lower risk of cognitive decline was consistent regardless of baseline cognitive level.
 
Conclusion: We found that higher diet quality was associated with a reduced risk of cognitive decline. Improved diet quality represents an important potential target for reducing the global burden of cognitive decline.
 
Assessment of diet quality. At baseline, we recorded participants' food intake using a qualitative Food Frequency Questionnaire (FFQ) containing 20 items (table e-2). Despite regional differences, this FFQ is applicable in different countries.15 The FFQ was administered after patients were checked for compliance with run-in drugs and confirmed eligibility (week 0). Participants were asked, "In the last 12 months, how often did you eat foods from each of the following categories?" for a standard list of food items. For these analyses, frequencies of consumption were converted to "times per day," and the association between diet quality and cognitive decline was determined using the modified Alternative Healthy Eating Index (mAHEI), which was developed to measure overall diet quality.16 The mAHEI has 7 components comprising the consumption of vegetables, fruits, nuts and soy proteins, whole grain, deep-fried foods, ratio of fish to meat and egg, and alcohol. Cutoff points for scoring were based on dietary recommendations, with a maximum of 10 points assigned when the dietary recommendation was met. A higher score indicates more frequent intake of healthy food choices (e.g., fruits, nuts and soy protein).16
 
DISCUSSION
 
To our knowledge, this is the first study to investigate the association between diet quality and cognitive impairment in a large multinational cohort of middle-aged and elderly people at high CV risk. In this large multinational cohort, we report that high diet quality is associated with a lower risk of cognitive decline, after controlling for known confounding factors over 5 years of follow-up. The association persisted after excluding those with major CV events during follow-up, those with cancer, those with MMSE score <24 at baseline, and those with cognitive decline during the first 2 years of follow-up, and using multiple definitions of cognitive decline.
 
To date, observational studies evaluating the association between diet quality, or its constituents (high intake of fruit and vegetables, nuts, fish, moderate alcohol intake, and low consumption of red meat), and cognitive decline report mixed findings; some report a positive association18 while others no association.6,19,20 Three recent systematic reviews explored the association between a Mediterranean diet and cognitive impairment and pooled analyses of 8 studies reported that moderate adherence to a Mediterranean diet was associated with a reduced risk of cognitive impairment.7,8,21 Similar to these reports, in this large multinational cohort study of middle-aged and elderly people, we observed a graded independent association between diet quality and cognitive decline. We also report novel information on the association between healthy eating and several subdomains of the MMSE.
 
The mechanism by which a healthy diet may lead to a reduced risk of cognitive decline requires further study. In addition to the established association between healthy diet and a reduction in overt stroke, a healthy diet may also reduce covert stroke (with resultant ischemia from microbleeds), although unproven. Foods rich in omega-3 fatty acids, vitamins C and E, folate, and other carotenoids may alter inflammatory pathways via reductions in oxidative stress and lipid peroxidation.8 In our cohort of people at high CV risk, the risk of covert stoke was expected to be high, as well as other CV events, such as hospitalization for CHF, that may also increase the risk of cognitive decline.
 
Of note, the association between diet quality and cognitive decline persisted when participants with major CV events during follow-up were excluded. Modifying risk factors for covert stroke such as hypertension, independent of diet quality, could also indirectly modify cognitive decline. For example, diets high in fruits and vegetables, which are rich in potassium, may lower blood pressure and reduce the risks of stroke and cognitive decline. We previously reported that a healthy diet was associated with a reduced risk of recurrent CV events, which lends support to the suggested mechanism in those with established CV disease.16 In addition, our analyses of MMSE components demonstrate a preferential association with domains that are prominent in vascular cognitive impairment (e.g., executive function).
 
Our study has several strengths including the large number of patients and outcome events (.4,000), the international cohort, detailed information on covariates, and the high completeness of data (99.8%). The method used to measure diet, the short FFQ, is reported to be a reliable measure of dietary intake by previous studies.15,16 Similarly, the method used to measure cognitive function, the MMSE, is a validated and widely used method of cognitive assessment, although it may have poor sensitivity for the detection of mild cognitive impairment, subtle changes in word recall, or impairment in executive function.22,23
 
Our study has a number of limitations. First, because this is an observational study, we can only establish association and not causation, and the effect of residual confounding cannot be ruled out, as dietary habits tend to be lifelong and may be a proxy for other poor health behaviors that were either unknown or unmeasured. Although we adjusted for BMI and physical activity, we chose not to also adjust for energy (caloric) intake because of the effect of multicollinearity and risk of overadjustment.24 Second, diet quality was measured only at baseline and we were unable to assess change in diet during follow-up. However, significant changes in dietary habits would be unlikely to occur over the length of follow-up of this study, including in those with incident CV events.25 In addition, those with incident CV disease would be more likely to change from unhealthy to healthy dietary patterns during follow-up, which would more likely bias toward the null. Third, our findings may partly be explained by reverse causation, as those at higher disease burden at baseline may be more likely to experience outcomes during follow-up. However, when we excluded participants with early cognitive decline (during the first 2 years of follow-up), the observed associations were materially unchanged. Fourth, dietary assessment by short FFQ in those with cognitive impairment at baseline may not accurately represent diet-disease association because the dietary assessment may not be as reliable and diet quality is unlikely to reverse established cognitive impairment. However, sensitivity analyses, excluding those with MMSE score <24 at baseline, did not materially alter the observed associations.
 
In conclusion, we report that higher diet quality is associated with a reduced risk of cognitive decline. Improved diet quality represents an important potential target for reducing the global burden of cognitive decline.
 
Diet is reported to be a potential risk factor for noncommunicable diseases including cardiovascular (CV) disease, Alzheimer disease, and vascular cognitive impairment. Dietary intake may modify the risk of cognitive decline through multiple mechanisms including increased risk of stroke (both overt and covert) and through deficiency of nutrients required for neuronal regeneration (e.g., group B vitamins, and vitamin C).1 However, the association between overall diet quality and cognitive impairment is uncertain. Although some cohort studies did not report any association between a Mediterranean-style diet and cognitive decline,2-4 others reported that adherence to a Mediterranean diet is associated with slower cognitive decline.5,6 Three recent systematic reviews reported that moderate adherence to a Mediterranean diet is associated with reduced risk of cognitive impairment.7-9 In addition, one study reported that a Western diet (vs Oriental diet) was associated with a reduced risk of Alzheimer disease.10 More precise associations between diet (assessed using standardized methodology) and cognitive outcomes may be observed in a large multinational prospective cohort study. The ONTARGET11 (Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial) and TRANSCEND12 (Telmisartan Randomised Assessment Study in ACE Intolerant Subjects with Cardiovascular Disease) studies provide a unique opportunity to investigate the association between diet quality and cognitive decline in a population at high risk of CV disease.
 
RESULTS In 27,860 participants included in these analyses, the median mAHEI score was 24.4 (minimum 3.1, maximum 66.7) and baseline mean (SD) MMSE score was 27.7 (2.8). Participants with higher mAHEI scores (healthiest diet) were slightly older, more active, less likely to smoke, had a lower BMI, normal serum creatinine, and had higher MMSE score (p , 0.001) (table 1).
 
Diet quality and risk of cognitive decline. Cognitive decline occurred in 4,699 participants (16.8%) during follow-up. After multivariable adjustment, we observed an inverse association between diet quality and risk of cognitive decline. Comparing healthiest vs unhealthiest diet, the highest quintile of mAHEI was associated with a reduction in risk of cognitive decline (hazard ratio [HR] 0.76, 95% confidence interval [CI] 0.66- 0.86) (figure 1) (p for trend ,0.01).
 
Sensitivity analyses. The healthiest diet (Q5) continued to be associated with a reduced risk of cognitive decline after excluding those with a major CV event (HR 0.77, 95% CI 0.67-0.89), those with cancer (HR 0.76, 95% CI 0.66-0.88), those with baseline MMSE score<24 (HR 0.74, 95% CI 0.65-0.85), and those with cognitive decline during the first 2 years (HR 0.65, 95% CI 0.53-0.79). We observed similar associations between categories of baseline MMSE (although a small number of participants had baseline MMSE score <26) and physical activity (figure 2). The overall pattern of association between mAHEI and cognitive decline was similar using multiple definitions of cognitive decline (figure 3). MMSE domains. After multivariable adjustment, we observed a significant association between higher diet quality and reduced risk of decline in 4 components of the MMSE, including copying, attention and calculation, registration, and writing (p<0.05) (table 2).
 
 
 
 
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