Introduction
Dietary Patterns and Cognitive Health During Ageing
The Mediterranean Diet
Study | Cohort details | Dietary pattern | Cognitive outcome measures | Key findings |
---|---|---|---|---|
Cross-sectional studies | ||||
Cognitive impairment and dietary habits among elders: the Velestino Study [53] | N = 557 ≥ 65 years Greece | MD | MMSE < 24 or ≥ 24 | MD adherence was positively associated with better MMSE score among men only. For women, an inverse association was detected. |
Mediterranean diet and cognitive function: a French study [54] | N = 3083 ~ 52.0 years France | MD | Episodic memory, lexical- semantic memory, short term and working memory, mental flexibility | Low MD adherence was associated with poorer performance in one measure of attention, processing speed, and working memory. |
Mediterranean diet and mild cognitive impairment [55] | N = 1875 (N = 1393 cognitively normal, N = 482 MCI) > 70 years USA | MD | Incidence of MCI and progression from MCI to AD. | Compared to those with the lowest MD adherence, those at the highest MD adherence had a 28% less risk of developing MCI and a 48% less risk of developing AD. |
Adherence to a Mediterranean diet and Alzheimer’s disease risk in an Australian population [56] | N = 970 (723 healthy controls (HC), 98 MCI and 149 AD) > 70 years Australia | MD | Mini-Mental State Examination, Logical, Memory II (WMS; Story 1 only), California Verbal Learning Test II—Second Edition (long delay) Delis-Kaplan Executive Function System Verbal Fluency | One unit increase in MD score was associated with 13–19% lower odds of MCI, and 19–26% lower odds of AD. |
Mediterranean diet and functional indicators among older adults in non-Mediterranean and Mediterranean countries [57] | N = 2791 US National Health and Nutrition Survey (NHANES) USA N = 1786 from Israeli National Health and Nutrition Survey (MABAT ZAHAV) Israel > 70 years | MD | NHANES - Wechsler adult intelligence scale, third edition digit symbol MABAT ZAHAV - MMSE | A greater MD adherence was associated with better cognitive function among both cohorts. |
Neuroprotective diets are associated with better cognitive function: the health and retirement study [58] | N = 5907 > 60 years USA | MD | Global Cognition | Greater MD adherence was associated with better cognitive function. |
Mediterranean diet and magnetic resonance imaging-assessed brain atrophy in cognitively normal individuals at risk for Alzheimer’s disease [45] | N = 52 ~ 54 years USA | MD | 3D T1-weighted MRI scanning to provide estimates of cortical thickness for entorhinal Cortex (EC), inferior parietal lobe, middle temporal gyrus, orbitofrontal cortex (OFC) and posterior cingulate cortex (PCC) | MD adherence was associated with greater cortical thickness of AD-vulnerable regions. |
Mediterranean diet and brain structure in a multi-ethnic elderly cohort [42] | N = 674 ~ 80 years USA | MD | Total brain volume (TBV), total grey matter volume (TGMV), total white matter volume (TWMV), mean cortical thickness (mCT), and regional volume or CT were derived from MRI scans | Compared to low MD adherence, higher MD adherence was associated with larger TBV, TGMV, and TWMV. |
Mediterranean diet, micronutrients and macronutrients, and MRI measures of cortical thickness [48] | N = 672 ~ 80 years USA | MD | Magnetic resonance imaging measures of cortical thickness | Higher MD score was associated with larger frontal, parietal, occipital thickness and average lobar cortical thickness. |
Longitudinal studies | ||||
Adherence to a Mediterranean diet, cognitive decline, and risk of dementia [27] | N = 1410 ~ 76 years France | MD | Mini-Mental State Examination (MMSE), Isaacs Set Test (IST), Benton,Visual Retention Test (BVRT), and Free and Cued Selective Reminding Test (FCSRT), Incident cases of dementia | Higher MD score was associated with fewer MMSE errors, but not with other cognitive test scores. MD adherence was not associated with the risk for incident dementia. |
Diet, physical activity and cognitive impairment among elders: the EPIC–Greece cohort (European Prospective Investigation into Cancer and Nutrition) [59] | N = 732 ≥ 60 years Greece | MD | Mini-Mental State Examination (MMSE) | Adherence to the MD was not associated with MMSE. |
Vegetables, unsaturated fats, moderate alcohol intake, and mild cognitive impairment [60] | N = 1233 ≥ 70 years USA | MD | Incident MCI and dementia | Higher MD adherence was associated with lower risk of incident MCI or dementia. |
Adherence to a Mediterranean diet and risk of incident cognitive impairment [61] | N = 17,478 ~ 64 years USA | MD | Incident cognitive impairment using a 6 item screen | Higher MD adherence was associated with less likelihood of incident cognitive impairment. |
The Mediterranean diet is not related to cognitive change in a large prospective investigation: the PATH through life study [62] | N = 1528 60–64 years Australia | MD | Incident MCI | MD was not associated with cognitive decline. |
Mediterranean diet habits in older individuals: Associations with cognitive functioning and brain volumes [63] | N = 194 ~ 75 years Sweden | MD | Seven minute screening (7MS) test; brain volume measured by volumetric magnetic resonance imaging | No associations between MD and 7MS nor volumes of grey matter and white matter in the fully adjusted models. |
Mediterranean diet and cognitive decline in women with cardiovascular disease or risk factors [64] | N = 2504 (women) ≥ 65 years USA | MD | Telephone Interview of Cognitive Status (TICS), telephone adaptation of the Mini-Mental State Examination (MMSE). TICS 10-word list (immediate and delayed recalls) and the East Boston Memory Test (immediate and delayed recalls), Category fluency test. | MD was not related to cognitive decline. |
Relation of DASH and Mediterranean-like dietary patterns to cognitive decline in older persons [33] | N = 826 ~ 82 years USA | MD DASH | Change in: Episodic memory, semantic memory, perceptual organisation, perceptual speed, working memory and global cognition | Higher MD score was associated with slower decline in episodic memory, semantic memory, working memory and global cognition. Higher DASH score was associated with slower rates of decline in episodic memory, semantic memory and global cognition. |
Long-term adherence to the Mediterranean diet is associated with overall cognitive status, but not cognitive decline, in women [65] | N = 16,058 ≥ 70 years Women USA | MD | Change in Telephone Interview for Cognitive Status (TICs), verbal memory, global cognition | MD score was associated with better cognitive performance on tests but not with decline in TICs, or composite scores of verbal memory and global cognition. |
Mediterranean diet and cognitive function: The SUN project [66] | N = 823 ~ 62 years Spain | MD | Cognitive function by Telephone Interview of Cognitive Status –modified (TICS-m) | Greater cognitive decline was observed among participants with low or moderate baseline adherence to the MD than among those with better adherence. |
Dietary patterns and cognitive decline among Chinese older adults [67] | N = 1650 > 55 years China | MD | Repeated measures of global cognitive scores, composite cognitive z-scores (standardised units [SU]), and standardised verbal memory scores (SU). | Higher MD adherence was associated with a slower rate of cognitive decline. |
Mediterranean lifestyle in relation to cognitive health: results from the HELIAD study [68] | N = 1716 ≥ 65 years Greece | MD | Diagnosis of Mild Cognitive Impairment (MCI), a composite Z-score for global cognitive functioning and Z-scores for 5 domains: memory, language, attention-speed of information processing, and executive and visual-spatial functioning | Greater MD adherence was associated with better cognitive performances in the domains of memory, visual- spatial functioning and language and composite cognitive Z –score. |
Mediterranean diet and preserved brain structural connectivity in older subjects [46] | N = 146 ~ 73 years France | MD | 3-T magnetic resonance imaging measuring Brain Grey matter and White matter volumes as well as a battery of neuropsychological tests | Greater MD adherence was significantly associated with preserved white matter microstructure in extensive brain areas. |
Mediterranean diet is associated with slower rate of hippocampal atrophy: a longitudinal study in cognitively normal older adults [43] | N = 215 ~ 79 years USA | MD | Magnetic resonance imaging scans to assess change of hippocampal volumes (intracranial volume adjusted) | Higher MD adherence was associated with slower atrophy for total hippocampal volume, by approximately 2.5 years. |
Mediterranean-type diet and brain structural change from 73 to 76 years in a Scottish cohort [44] | N = 562 72.65 ± 0.72 years UK | MD | Brain volume (total and grey matter) and cortical thickness using MRI imaging | Lower MD adherence was associated with greater 3-year reduction in total brain volume. |
Mediterranean diet adherence and rate of cerebral Aβ-amyloid accumulation: data from the Australian Imaging, Biomarkers and Lifestyle Study of Ageing [47] | N = 77 ~ 71 years Australia | MD | Cerebral Aβ load using compound B positron emission tomography | Higher MD score was associated with less Aβ accumulation. |
Prospective study of dietary approaches to stop hypertension and Mediterranean style dietary patterns and age-related cognitive change: the Cache County Study on Memory, Health and Ageing [69] | N = 3831 ≥ 65 years USA | MD DASH | Modified Mini-Mental State Examination (3MS) | Higher DASH and MD scores were associated with higher average 3MS scores. People in quintile 5 of DASH averaged 0.97 points higher than those in quintile 1. The corresponding difference for Mediterranean quintiles was 0.94. |
No association between dietary patterns and risk for cognitive decline in older women with 9-year follow-up: data from the women’s health initiative memory study [70] | N = 6425 65–79 years USA | MD DASH | Cognitive decline was defined as cases of MCI or probable dementia (PD) | MD or DASH scores were not associated with MCI or PD. |
Intervention studies | ||||
Mediterranean diet improves cognition: the PREDIMED- NAVARRA randomised trial [2] | N = 522 74.6 ± 5.7 Spain | MD supplemented with olive oil or nuts vs low fat diet (control) | Global cognition measured by MMSE and Clock Drawing Test | Participants in the MD and olive oil and MD and nuts groups had higher mean cognitive scores than the control group. |
Virgin olive oil supplementation and long-term cognition: the PREDIMED- NAVARRA randomised trial [71] | N = 285 74.1 ± 5.7 years Spain | MD supplemented with olive oil or nuts vs low fat diet (control) | Episodic memory, Verbal memory, Visual memory, Visuospatial abilities, Language Fluency, Executive function, Attention, Working memory, Abstract reasoning | The MD and olive oil group had a significantly better performance across fluency and memory compared to control. The MD and nuts group did not differ in cognitive performance in comparison to the control group. |
Mediterranean diet and age-related cognitive decline: a randomised clinical trial [4] | N = 334 ~ 66.9 years Spain | MD supplemented with olive oil or nuts vs low fat diet (control) | Change in: Global cognition, Memory, Frontal (attention + executive function) | In comparison to the control, those in the MD and nuts group showed significant improvement in memory whereas those in the MD and olive oil group showed improvement in global cognition and frontal composite scores. |
The Mediterranean diet and cognitive function among healthy older adults in a 6-month randomised controlled trial: the MedLey Study [72] | N = 137 72.1 ± 5.0 years Australia | MD vs habitual diet | Neuropsychological test battery, including 11 individual tests | Adherence to a MD had no significant effect on overall age-related cognitive performance. |
Effect of the NU-AGE diet on cognitive functioning in older adults: a randomised controlled trial [73] | N = 1279 70.9 ± 3.4 years Five European centres in France, Italy, the Netherlands, Poland, and the United Kingdom (UK) | NU-AGE diet (individually tailored Mediterranean-like diet advice vs habitual diet (advice on national dietary guidelines) | Consortium to Establish a Registry for Alzheimer’s Disease (CERAD)-Neuropsychological Battery and five additional domain-specific single cognitive tests | Both control and intervention groups showed improvements in global cognition and in all cognitive domains after 1 year, but differences between the two groups were not statistically significant. |
Effects of the dietary approaches to stop hypertension diet, exercise, and caloric restriction on neurocognition in overweight adults with high blood pressure [3] | N = 124 52.3 ± 9.6 years USA | DASH diet alone vs DASH combined with a behavioural weight management program including exercise and caloric restriction vs a usual diet control group. | Battery of neurocognitive tests to assess performance in the domains of executive function-memory-learning (EFML) and psychomotor speed | Compared to control, DASH combined with a behavioural weight management program improved EFML and psychomotor speed and DASH diet alone improved psychomotor speed. |
Lifestyle and neurocognition in older adults with cognitive impairments: a randomised trial [74] | N = 160 65.4 ± 6.8 years USA | Aerobic exercise vs no exercise and DASH diet vs no DASH diet (health education) | Pre-specified composite measure of executive function; measures of language/verbal fluency, memory, and ratings on the modified Clinical Dementia Rating Scale | No effect of DASH diet on cognitive function. [74] The largest improvement in cognitive function was reported in response to combined exercise and DASH. |
The Dietary Approaches to Stop Hypertension Diet
Inflammatory Mechanisms of Dietary Action on Cognitive Function
Effects of Diet on Neuroinflammation
Indirect Inflammatory Actions of Diet on Neuroinflammation
Systemic Inflammation
Study | Cohort details | Dietary pattern | Cognitive outcome measures | Key findings |
---|---|---|---|---|
Dietary pattern, inflammation and cognitive decline: The Whitehall II prospective cohort study [89] | N = 5083 56.0 years UK Longitudinal Study | Inflammatory dietary pattern characterised by higher intake of red meat, processed meat, peas and legumes, and fried food, and lower intake of whole grains which correlated with elevated IL-6 using reduced rank regression (RRR) | 3 clinical examinations over 10 years were administered for the cognitive test battery and consisted of 4 standard tasks: Alice Heim 4-I, short-term verbal memory, phonemic fluency, and semantic fluency | A greater decline in reasoning was seen in participants in the highest tertile of adherence to the inflammatory dietary pattern compared to those in the lowest tertile after adjustment for confounding variables. |
An Inflammation-related Nutrient Pattern is Associated with Both Brain and Cognitive Measures in a Multi-ethnic Elderly Population [90] | N = 330 79.0 years USA Cross Sectional Study | RRR was performed using 24 predetermined nutrients as predicting variables and two inflammatory biomarkers (CRP and IL6) as response variables. The inflammatory nutrient pattern (INP) was characterised by low intakes of calcium, vitamin D, vitamins E, A, B1, B2, B3, B5, B6, folate, omega-3 PUFA, and high intake of cholesterol | MRI imaging of global brain measures including intra-cranial volume (ICV), total brain volume (TBV), total grey matter volume (TGMV), and total white matter volume (TWMV). Cognitive ability at the time of MRI scan visit was measured with a neuropsychological battery | Each unit increase in inflammatory nutrient pattern was significantly associated with 36.8 cm3 smaller total brain volume and 0.21 lower visuospatial z-score. |
Long-term association between the dietary inflammatory index and cognitive functioning: findings from the SU.VI.MAX study [91] | N = 3080 52.0 ± 4.6 years France | Dietary Inflammatory Index (DII) reflecting the overall inflammatory potential of the diet | Neuropsychological Evaluation including episodic memory, lexical–semantic memory, short-term and working memory | There was a strong inverse association observed between a higher DII (reflecting a more inflammatory diet) and overall cognitive functioning. With regard to specific cognitive domains, similar associations were observed with scores reflecting verbal memory, but not executive functioning. |
Inflammatory potential of diet is associated with cognitive function in an older adult Korean population [92] | N = 239 74.0 years Korea | Energy adjusted dietary inflammatory index (E-DII) reflecting the overall inflammatory potential of the diet | Korean-adjusted version of the Mini-Mental State Examination (K-MMSE) | E-DII scores were significantly inversely associated with K-MMSE score in both unadjusted and adjusted models, after controlling for confounding variables. Participants in the highest E-DII tertile (reflecting a more inflammatory diet) had increased risk for mild or moderate cognitive impairment compared with those in the lowest E-DII tertile. |
The association between an inflammatory diet and global cognitive function and incident dementia in older women: The Women’s Health Initiative Memory Study [93] | N = 7085 71.0 ± 3.9 years USA | Dietary Inflammatory Index (DII) reflecting the overall inflammatory potential of the diet | Cognitive function was evaluated annually, and MCI and all-cause dementia cases were adjudicated centrally | Higher DII scores (reflecting a more inflammatory diet) were associated with greater cognitive decline and earlier onset of cognitive impairment. |
Dietary inflammatory index and memory function: population-based national sample of elderly Americans [94] | N = 1723 68.4 ± 0.2 years USA | Dietary Inflammatory Index (DII) reflecting the overall inflammatory potential of the diet | Consortium to Establish a Registry for Alzheimer’s disease (CERAD) Word Learning subset, the Animal Fluency test, and the Digit Symbol Substitution Test (DSST) | Episodic memory (CERAD), semantic-based memory (Animal Fluency Test) and executive function and working-memory (DSST) performances were lowest among those with the highest mean DII score (reflecting a more inflammatory diet). |