Nutrition and prevention of cognitive impairment

Association of solid fuel use with cognitive function and the modifying role of lifestyle: A nationwide cohort study in China

BACKGROUND

As opposed to a healthy lifestyle, indoor air pollution from solid fuel use may be harmful for cognitive function. However, the extent to which lifestyle modifies the association between solid fuel use and cognitive function remains unknown.

METHODS

A total of 21,008 individuals aged 16 to 92 were enrolled in 2010 and followed up to 2014 in the China Family Panel Studies (CFPS). Cognitive function was assessed using standardized math and word tests in two waves. Solid fuel use at baseline was assessed by self-reporting of firewood, straw, or coal used for cooking. Lifestyle profile was classified into two groups (favorable vs. unfavorable) based on five modifiable lifestyle factors including alcohol drinking, smoking, body mass index, diet, and physical activity. Linear mixed-effects models were employed to assess the association of solid fuel use and lifestyle with cognitive function. The effect modification of lifestyle was analyzed.

RESULTS

A total of 49.7% of the study population used solid fuels for cooking and 17.4% had a favorable lifestyle. Solid fuel use was associated with a significant decrease in cognitive function (β = -0.29, 95% CI: -0.39, -0.19 for math test; β = -0.62, 95% CI: -0.84, -0.41 for word test). Lifestyle significantly modified this association (p-interaction: 0.006 for math test; 0.016 for word test), with the corresponding association being less pronounced among participants adhering to a favorable lifestyle compared to those with an unfavorable lifestyle.

CONCLUSION

A favorable lifestyle may attenuate the adverse association between solid fuel use and cognitive function. Adopting a favorable lifestyle has the potential to mitigate the adverse neurological effects due to indoor air pollution.

Predicting Alzheimer's disease from cognitive footprints in mid and late life: How much can register data and machine learning help?

BACKGROUND

Real-world data with decades-long medical records are increasingly available alongside the growing adoption of machine learning in healthcare research. We evaluated the performance of machine learning models in predicting the risk of Alzheimer's disease (AD) using data from the Finnish national registers.

METHODS

We conducted a case-control study using data from the Finnish MEDALZ (Medication use and Alzheimer's disease) study. Altogether 56,741 individuals with incident AD diagnosis (age ≥ 65 years at diagnosis and born after 1922) and their 1:1 age-, sex-, and region of residence-matched controls were included. The association of risk factors, evaluated at different age periods (45-54, 55-64, 65+), and AD were assessed with logistic regression. Predictive accuracies of logistic regressions were compared with seven machine learning models (L1-regularized logistic regression, Naive bayes, Decision tree, Random Forest, Multilayer perceptron, XGBoost, and LightGBM).

FINDINGS

63.5 % of cases and controls were females and the mean age was 79.1 (SD = 5.1). The strongest associations with AD were observed for head injuries at age 55-64 (OR, 95 % CI 1.33, 1.19-1.48) and 65+ (1.31, 1.23-1.40), followed by antidepressant use (1.30, 1.22-1.38) at 55-64 and antipsychotic use (1.27, 1.19-1.35) at 65+. The predictive accuracies of all models were low, with the best performance (AUC 0.603) observed in Random Forest for predicting AD onset at age 65-69.

INTERPRETATION

Although significant associations were identified between many risk factors and AD, the low predictive accuracies suggest that specialised healthcare diagnosis data is not sufficient for predicting AD and linkage with other data sources is needed.

Association of adherence to the EAT-Lancet diet with risk of dementia according to social economic status: a prospective cohort in UK Biobank

The EAT-Lancet Commission has proposed a reference diet aiming to promote human health and environmental sustainability. Socioeconomic disadvantage and poor diet are well-known risk factors for dementia; however, whether the effect of this reference diet on dementia varies by socioeconomic status has not been investigated. The dietary habits of 190,893 participants from UK-Biobank were assessed; the association of EAT-Lancet diet with incident dementia across socioeconomic status was determined by Cox models. One thousand seven hundred twenty-eight dementia cases were identified during a median of 12.24 years follow-up. An inverse association between adherence to EAT-Lancet diet and all-cause dementia (high vs. low; hazard ratio [HR], 95% confidence interval [CI]: 0.82, 0.72-0.94) or late-onset dementia (high vs. low; HR, 95% CI: 0.78, 0.68-0.91) was observed only in individuals with high socioeconomic status. On the contrary, no protective effects of EAT-Lancet diet on early-onset dementia were observed, regardless of the socioeconomic status. Our findings indicated that adherence to an environment-friendly diet helps attenuate risk of dementia only in individuals with high socioeconomic level.

Medium-chain triglycerides combined with DHA improve cognitive function by inhibiting neurocyte apoptosis of the brain in SAMP8 mice

Medium-chain triglycerides (MCTs) and docosahexaenoic acid (DHA, Cn-3, 22:6) are essential in improving cognitive function and protecting neurocytes. This study explored the effects of the combined intervention of MCTs and DHA on inhibiting neurocyte apoptosis of the brain and improving cognitive function in senescence-accelerated mouse-prone 8 (SAMP8). Four-month-old male SAMP8 mice were randomly divided into four treatment groups (12 mice/group): DHA, MCT, DHA + MCT, and control groups, which intervened for seven months. Twelve age-matched male senescence-accelerated mouse resistant 1 (SAMR1) was used as the natural aging group. TUNEL assay and HE staining were used to assess neurocyte apoptosis and damage in the brain of mice. Moreover, the cognitive function was analyzed using the Morris water maze (MWM) and open field (OF) tests. The results showed that the cognitive function of 11-month-old SAMP8 mice decreased with age, and further pathological examination revealed the damaged neurocyte structure, karyopyknosis, cell atrophy, and even apoptosis. MCTs combined with DHA supplementation could increase octanoic acid (C8:0), decanoic acid (C10:0), and DHA levels in the serum, inhibit neurocyte apoptosis, improve neurocyte damage, moreover delay age-related cognitive decline after seven-month treatment. Furthermore, combining MCTs and DHA was significantly more beneficial than MCTs or DHA alone. In conclusion, MCTs combined with DHA could delay cognitive decline by inhibiting neurocyte apoptosis of the brain in SAMP8 mice.

Potential of dietary polyphenols for protection from age-related decline and neurodegeneration: a role for gut microbiota?

Many epidemiological studies have shown the beneficial effects of a largely plant-based diet, and the strong association between the consumption of a Mediterranean-type diet with healthy aging including a lower risk of cognitive decline. The Mediterranean diet is characterized by a high intake of olive oil, fruits and vegetables and is rich in dietary fiber and polyphenols - both of which have been postulated to act as important mediators of these benefits. Polyphenols are large molecules produced by plants to protect them from environmental threats and injury. When ingested by humans, as little as 5% of these molecules are absorbed in the small intestine with the majority metabolized by the gut microbiota into absorbable simple phenolic compounds. Flavan-3-ols, a type of flavonoid, contained in grapes, berries, pome fruits, tea, and cocoa have been associated with many beneficial effects on several risk factors for cardiovascular disease, cognitive function and brain regions involved in memory formation. Both preclinical and clinical studies suggest that these brain and heart benefits can be attributed to endothelial vascular effects and anti-inflammatory properties among others. More recently the gut microbiota has emerged as a potential modulator of the aging brain and intriguingly polyphenols have been shown to alter microbiota composition and be metabolized by different microbial species. However, there is a need for well controlled studies in large populations to identify predictors of response, particularly given the vast inter-individual variation of human gut microbiota.

Association of the serum levels of saturated fatty acids and mild cognitive impairment: a cross-sectional study

OBJECTIVES

To investigate the association of serum saturated fatty acids (SFAs) and prevalent mild cognitive impairment (MCI) among middle-aged and elderly Chinese.

METHODS

A total of 607 Chinese adults aged at least 45 years were included in the baseline survey of The Lifestyle and Healthy Aging of Chinese Square Dancer Study. Serum concentrations of individual SFAs including 6 even-chain SFAs (C14:0, C16:0, C18:0, C20:0, C22:0, and C24:0) and 4 odd-chain SFAs (C15:0, C17:0, C21:0, and C23:0), were quantified by Gas chromatography system with a mass spectrometer. According to Petersen's criteria, prevalent MCI was diagnosed by neurologists through uniformed neuropsychological tests, including trail-making test-part B (TMT-B), auditory verbal learning test (AVLT), digit symbol substitution test (DSST), and verbal fluency test (VFT).

RESULTS

The median age was 62 years with an interquartile range of 57.0 to 67.0 years, and 86 (14.17%) participants were living with MCI. Higher levels of either even-chain or odd-chain individual SFAs were associated with the higher odds of MCI, and their odds ratios (ORs) and 95% confidence intervals (95%CIs) were 2.054 (1.012 to 4.171) for C14:0, 2.246 (1.061 to 4.755) for C16:0, 2.789 (1.321 to 5.886) for C18:0, and 2.329 (1.136 to 4.778) for C15:0, and 2.761 (1.310 to 5.820) for C17:0, respectively.

CONCLUSIONS

The serum concentration of SFAs was positively related to the odds of MCI in middle-aged and elderly adults. Determining the link between SFAs profiles and MCI may inform a better understanding of the potential role of saturated fat intake on cognitive function.

Long-term effects of an egg-protein hydrolysate on cognitive performance and brain vascular function: a double-blind randomized controlled trial in adults with elevated subjective cognitive failures

PURPOSE

Short-term intake of the egg-protein hydrolysate Newtricious (NWT)-03 improved executive function, but underlying mechanisms and long-term effects, including other cognitive domains, are unknown.

METHODS

A 36-week randomized controlled trial involving 44 overweight/obese individuals experiencing elevated Subjective Cognitive Failures (SCF; aged 60-75 years) assessed the impact of daily consumption of 5.7 g of NWT-03 or placebo powders on cognitive performance (psychomotor speed, executive function, memory) and Cerebral Blood Flow (CBF), a marker of brain vascular function. Cognitive performance was evaluated using a neurophysiological test battery (CANTAB) and CBF was measured using magnetic resonance imaging perfusion method Arterial Spin Labeling (ASL). Serum samples were collected to determine brain-derived neurotrophic factor (BDNF) concentrations.

RESULTS

Anthropometrics, and energy and nutrient intakes remained stable throughout the trial. NWT-03 was well tolerated, and compliance was excellent (median: 99%; range: 87-103%). No overall intervention effects were observed on cognitive performance or CBF, but post-hoc analyses revealed significant improvements on executive function in women, but not men. Specifically, a reduction of 74 ms in reaction latency on the multitasking task (95% CI: -134 to -15; p = 0.02), a reduction of 9 between errors (95%CI: -14 to -3; p < 0.001), and a reduction of 9 total errors (95%CI: -15 to -3; p < 0.001) on the spatial working memory task were found in women. No intervention effects were observed on serum BDNF concentrations (p = 0.31).

CONCLUSION

Long-term consumption of NWT-03 improved multitasking abilities and working memory in women with elevated SCF. Brain vascular function remained unaffected. Sex differences in executive function require additional clarification.

Energy-adjusted dietary inflammatory index and cognitive function in Chinese older adults: a population-based cross-sectional study

Diet can regulate systemic inflammation, which may play an important role in the development and progression of cognitive impairment and dementia. To explore the relationship between the dietary inflammatory potential and cognitive ability. A total of 2307 adults aged 60 years or older were recruited from the Fujian Provincial Hospital (Fujian, China). Dietary inflammatory properties were analyzed using the energy-adjusted dietary inflammatory index (E-DII). The Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) were used to assess cognitive function. Logistic regression and restricted cubic spline (RCS) were fit to assess the associations between variables. The MCI subjects with the highest E-DII scores had a higher risk of AD compared to subjects with the lowest E-DII scores (OR = 1.98, 95%CI = 1.49-2.64, P for trend < 0.001). Subjects with the highest E-DII levels were at increased risk of cognitive impairment compared to those with the lowest E-DII levels (OR = 1.56, 95%CI = 1.25-1.93, P for trend < 0.001). The link between E-DII and cognitive impairment was significant in a nonlinear dose response analysis (P for nonlinear = 0.001). Higher E-DII scores were associated with an increased risk of developing AD or cognitive impairment. These findings may contribute to the effective prevention of cognitive impairment by constructing a multidisciplinary synergistic prevention strategy and controlling dietary inflammation levels.

Association between Life's Essential 8 and cognitive function among older adults in the United States

The American Heart Association (AHA) recently redefined cardiovascular health (CVH) with the introduction of Life's Essential 8 (LE8), which encompasses eight areas (diet, physical activity, nicotine exposure, sleep duration body mass index, non-HDL cholesterol, blood glucose, and blood pressure). This study aimed to explore the relationships between both the aggregate and individual CVH metrics, as defined by Life's Essential 8, and cognitive function in older adults in the United States. This cross-sectional, population-based study analyzed data from the National Health and Nutrition Examination Survey conducted between 2011 and 2014, focusing on individuals aged 60 years and older. CVH was categorized as low (0-49), moderate (50-79), or high (80-100). Cognitive function was assessed through the CERAD tests, Animal Fluency test, and Digit Symbol Substitution test. Multivariable logistic models and restricted cubic spline models were employed to investigate these associations. This study included a total of 2279 older adults in the United States. Only 11% of adults achieved a high total CVH score, while 12% had a low score. After further adjustment for potential confounding factors, higher LE8 scores were significantly associated with higher scores on CERAD: delayed recall score (0.02[0.01, 0.03]; P < 0.001), CERAD: total score (3 recall trials) (0.04[0.02, 0.06]; P < 0.001), animal fluency: total score (0.09[0.05, 0.12]; P < 0.001), and digit symbol: score (0.29[0.18, 0.41]; P < 0.001), demonstrating a linear dose-response relationship. Similar patterns were also observed in the associations between health behavior and health factor scores with cognitive function tests. LE8 scores exhibited positive linear associations with cognitive function. Maintaining better levels of CVH may be associated with higher levels of cognitive function in older Americans, but further research is needed to confirm the causal and temporal relationships between LE8 and cognitive function.

The Association between Individual Food Groups, Limbic System White Matter Tracts, and Episodic Memory: Initial Data from the Aiginition Longitudinal Biomarker Investigation of Neurodegeneration (ALBION) Study

(1) Background: Many studies link food intake with clinical cognitive outcomes, but evidence for brain biomarkers, such as memory-related limbic white matter (WM) tracts, is limited. We examined the association between food groups, limbic WM tracts integrity, and memory performance in community-dwelling individuals. (2) Methods: We included 117 non-demented individuals (ALBION study). Verbal and visual episodic memory tests were administered, and a composite z-score was calculated. Diffusion tensor imaging tractography was applied for limbic WM tracts (fornix-FX, cingulum bundle-CB, uncinate fasciculus-UF, hippocampal perforant pathway zone-hPPZ). Food intake was evaluated through four 24-h recalls. We applied linear regression models adjusted for demographics and energy intake. (3) Results: We found significant associations between (a) higher low-to-moderate alcohol intake and higher FX fractional anisotropy (FA), (b) higher full-fat dairy intake and lower hPPZ FA, and (c) higher red meat and cold cuts intake and lower hPPZ FA. None of the food groups was associated with memory performance. (4) Conclusions: Despite non-significant associations between food groups and memory, possibly due to participants' cognitive profile and/or compensatory mechanisms, the study documented a possible beneficial role of low-to-moderate alcohol and a harmful role of full-fat dairy and red meat and cold cuts on limbic WM tracts.

Selenoprotein H mediates low selenium-related cognitive decline through impaired oligodendrocyte myelination with disrupted hippocampal lipid metabolism in female mice

Low selenium levels are closely associated with reduced cognitive performance and lipid dysregulation, yet the mechanism of action remains unclear. The physiological function of selenium is primarily mediated by selenoproteins. Selenoprotein H (SELENOH), as one of the selenium-containing proteins, has an unelucidated role in regulating cognitive status and lipid metabolism. In this study, we established a Selenoh gene knockout (HKO) mouse model to investigate whether Selenoh mediates the impact of selenium on cognitive function. We found that HKO mice showed a significant decline in cognition compared with the wild-type (HWT) littermates, and were not affected by deficient or excessive selenium, while no differences in anxiety and depression behavior were observed. HKO mice showed reduced myelin basic protein expression in hippocampal oligodendrocytes, with decreased glycolipid levels and increased phospholipid and sphingolipid levels in the hippocampus. Furthermore, the high-fat diet (HFD) exerted no effect on cognition and limited impact on the gene profile in the hippocampus of HKO mice. Compared with those of HWT mice, the myelination pathways in the hippocampus of HKO mice were downregulated as revealed by RNA-seq, which was further confirmed by the reduced expression levels of myelin-related proteins. Finally, HKO increased the expression of hippocampal fatty acid transporter (FATP) 4, and HFD increased the FATP4 expression in HWT mice but not in HKO mice. In summary, our study demonstrated that HKO induced cognitive decline by impairing myelination in oligodendrocytes with disrupted hippocampal lipid metabolism, which provided a novel viewpoint on the selenoprotein-mediated neurodegenerative diseases of selenium.

Association between dietary magnesium intake, inflammation, and neurodegeneration

BACKGROUND

Consistent evidence shows that magnesium (Mg) intake is associated with lower blood pressure (BP), and that lower BP is associated with improved cerebral health. However, recent findings indicate that the positive effect of dietary Mg intake on cerebral health is not mediated by a decrease in BP. As Mg's anti-inflammatory action is a plausible alternative mechanism, the objective of this study was to investigate the associations between Mg intake and inflammation to determine whether it mediates any neuroprotective effect.

METHODS

Participants from the UK Biobank (n = 5775, aged 40-73 years, 54.7% female) were assessed for dietary magnesium using an online food questionnaire, brain and white matter lesion (WML) volumes were segmented with FreeSurfer software, and inflammation markers including high-sensitivity C-reactive protein (hs-CRP), leukocyte, erythrocyte count, and Glycoprotein acetylation (GlycA) were measured using specific laboratory techniques such as immunoturbidimetry, automated cell counting, and nuclear magnetic resonance. Hierarchical linear regression models were performed to investigate the association between dietary Mg, and inflammatory markers and between dietary Mg, brain and WMLs volumes. Mediation analysis was performed to test a possible mediation role of inflammation on the association between dietary Mg and brain and WMLs volumes.

RESULTS

Higher dietary Mg intake was associated with lower inflammation: hs-CRP level (- 0.0497%; 95% confidence interval [CI] - 0.0497%,  - 0.0199%) leukocytes count (- 0.0015%; 95%CI - 0.00151%,  - 0.0011%), and GlycA (- 0.0519%; 95%CI - 0.1298%,  - 0.0129%). Moreover, higher dietary Mg intake was associated with larger grey matter volume (0.010%; 95%CI 0.004%, 0.017%), white matter volume (0.012%; 95%CI 0.003,  0.022) and right hippocampal volume (0.002%; 95%CI 0.0007, -0.0025%). Lower hs-CRP levels mediated the positive association between higher dietary Mg intake and larger grey matter volume.

CONCLUSIONS

The anti-inflammatory effects of dietary Mg intake in the general population, appears to mediate its neuroprotective effect.

Understanding engagement in diet and dementia prevention research among British South Asians: a short report of findings from a patient and public involvement group

BACKGROUND

Dementia is a global public health challenge. Evidence suggests that individuals from South Asian communities are an at-risk group for dementia, partly as a result of early and cumulative exposure to known dementia risk factors, such as obesity and type 2 diabetes. There needs to be more culturally appropriate community engagement to increase awareness of dementia and identify better strategies to encourage participation in dementia-related research.

METHODS

We aimed to better understand the barriers and facilitators towards engaging with, and participating in, diet and dementia related research among British South Asians. This was achieved using a public and patient involvement (PPI) approach. A community-based, engagement event involving information sharing from experts and roundtable discussions with South Asian communities (n = 26 contributors) was held in June 2023 in Newcastle-upon-Tyne, UK. Collaboration from preidentified PPI representatives (n = 3) informed the content and structure of PPI activities, as well as recruitment. Data were synthesised using template analysis, a form of codebook thematic analysis. This involved deductively analysing data using relevant a priori themes, which were expanded upon, or modified, via inductive analysis.

RESULTS

The findings highlighted the importance of trust, representation and appreciation of cultural barriers as facilitators to engagement in diet and dementia risk reduction research. Consideration of language barriers, time constraints, social influences and how to embed community outreach activities were reported as driving factors to maximise participation.

CONCLUSIONS

This PPI work will inform the design and co-creation of a culturally adapted dietary intervention for brain health in accordance with the Medical Research Council and National Institute for Health and Care Research guidance for developing complex interventions.

The Mediterranean diet is not associated with neuroimaging or cognition in middle-aged adults: a cross-sectional analysis of the PREVENT dementia programme

BACKGROUND AND PURPOSE

The Mediterranean diet (MedDiet) has been associated with reduced dementia incidence in several studies. It is important to understand if diet is associated with brain health in midlife, when Alzheimer's disease and related dementias are known to begin.

METHODS

This study used data from the PREVENT dementia programme. Three MedDiet scores were created (the Pyramid, Mediterranean Diet Adherence Screener [MEDAS] and MEDAS continuous) from a self-reported food frequency questionnaire. Primary outcomes were hippocampal volume and cube-transformed white matter hyperintensity volume. Secondary outcomes included cornu ammonis 1 and subiculum hippocampal subfield volumes, cortical thickness and measures of cognition. Sex-stratified analyses were run to explore differential associations between diet and brain health by sex. An exploratory path analysis was conducted to study if any associations between diet and brain health were mediated by cardiovascular risk factors for dementia.

RESULTS

In all, 504 participants were included in this analysis, with a mean Pyramid score of 8.10 (SD 1.56). There were no significant associations between any MedDiet scoring method and any of the primary or secondary outcomes. There were no differences by sex in any analyses and no significant mediation between the Pyramid score and global cognition by cardiovascular risk factors.

CONCLUSIONS

Overall, this study did not find evidence for an association between the MedDiet and either neuroimaging or cognition in a midlife population study. Future work should investigate associations between the MedDiet and Alzheimer's disease and related dementias biomarkers as well as functional neuroimaging in a midlife population.

Dietary bitter ginger-derived zerumbone improved memory performance during aging through inhibition of the PERK/CHOP-dependent endoplasmic reticulum stress pathway

PERK/CHOP pathway-mediated excessive endoplasmic reticulum (ER) stress is closely linked to aging-related cognitive impairment (ARCD). Zerumbone (ZB), a naturally occurring sesquiterpene molecule obtained from dietary bitter ginger, has garnered significant interest due to its diverse range of biological properties. It is unclear, though, if ZB can reduce ARCD by preventing ER stress that is dependent on the PERK/CHOP pathway. Here, the PERK-CHOP ER stress pathway was the main focus of an evaluation of the effects and mechanisms of ZB for attenuating ARCD in D-galactose (D-gal)-induced aging mice and SH-SY5Y cells. According to our findings, ZB not only greatly decreased neuronal impairment both in vitro and in vivo, but also significantly alleviated learning and memory failure in vivo. ZB significantly reduced the activation of the PERK/CHOP pathway and neuronal apoptosis in vitro and in vivo, exhibiting the down-regulation of GRP78, p-PREK/PERK, and CHOP expression levels, in addition to suppressing oxidative damage (MDA drop and SOD rise). Comparable outcomes were noted in SH-SY5Y cells subjected to severe ER stress caused by TM. On the other hand, 4-PBA, an ER stress inhibitor, considerably reversed these modifications. Remarkably, CCT020312 (a PERK activator) dramatically overrode the inhibitory effects of ZB on the PERK/CHOP pathway and neuronal death in D-gal-induced SH-SY5Y cells. In contrast, GSK2606414 (a PERK inhibitor) significantly increased these effects of ZB. In summary, our results suggested that ZB prevented D-gal-induced cognitive deficits by blocking the PERK/CHOP-dependent ER stress pathway and apoptosis, suggesting that ZB might be a natural sesquiterpene molecule that relieves ARCD.

Nutrition guidance within a multimodal intervention improves diet quality in prodromal Alzheimer's disease: Multimodal Preventive Trial for Alzheimer's Disease (MIND-ADmini)

BACKGROUND

Multimodal lifestyle interventions can benefit overall health, including cognition, in populations at-risk for dementia. However, little is known about the effect of lifestyle interventions in patients with prodromal Alzheimer's disease (AD). Even less is known about dietary intake and adherence to dietary recommendations within this population making it difficult to design tailored interventions for them.

METHOD

A 6-month MIND-ADmini pilot randomized controlled trial (RCT) was conducted among 93 participants with prodromal AD in Sweden, Finland, Germany, and France. Three arms were included in the RCT: 1) multimodal lifestyle intervention (nutritional guidance, exercise, cognitive training, vascular/metabolic risk management, and social stimulation); 2) multimodal lifestyle intervention + medical food product; and 3) regular health advice (control group). Adherence to dietary advice was assessed with a brief food intake questionnaire by using the Healthy Diet Index (HDI) and Mediterranean Diet Adherence Screener (MEDAS). The intake of macro- and micronutrients were analyzed on a subsample using 3-day food records.

RESULTS

The dietary quality in the intervention groups, pooled together, improved compared to that of the control group at the end of the study, as measured with by HDI (p = 0.026) and MEDAS (p = 0.008). The lifestyle-only group improved significantly more in MEDAS (p = 0.046) and almost significantly in HDI (p = 0.052) compared to the control group, while the lifestyle + medical food group improved in both HDI (p = 0.042) and MEDAS (p = 0.007) during the study. There were no changes in macro- or micronutrient intake for the intervention groups at follow-up; however, the intakes in the control group declined in several vitamins and minerals when adjusted for energy intake.

CONCLUSION

These results suggest that dietary intervention as part of multimodal lifestyle interventions is feasible and results in improved dietary quality in a population with prodromal AD. Nutrient intakes remained unchanged in the intervention groups while the control group showed a decreasing nutrient density.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03249688, 2017-07-08.

Vitamin D deficiency stratifies the risk of covert and overt hepatic encephalopathy in patients with cirrhosis: A retrospective cohort study

BACKGROUNDS & AIMS

This study aimed to investigate the association between vitamin D deficiency and covert hepatic encephalopathy (CHE), overt hepatic encephalopathy (OHE) occurrence, and mortality in patients with cirrhosis.

METHODS

This retrospective study reviewed 679 patients with cirrhosis. Vitamin D deficiency was defined as serum 25-hydorxyvitamin D (25-OHD) levels < 20 ng/mL. The associations between 25-OHD and CHE, OHE occurrence, and mortality were assessed using logistic regression, Fine-Gray competing risk regression, and Cox proportional hazards regression models, respectively.

RESULTS

Of 428 eligible patients, 75% had vitamin D deficiency and 23% had CHE. The prevalence of CHE was higher in patients with vitamin D deficiency than in those without vitamin D deficiency (28% vs. 13%, p = 0.002). During the median follow-up period of 2.3 years, 14% of the patients developed OHE and 27% died. Patients with vitamin D deficiency had a higher incidence of OHE (p = 0.002) and mortality (p = 0.006) than those without vitamin D deficiency. After adjustment for potential covariates, multivariate analyses showed that 25-OHE was associated with CHE (odds ratio, 0.95; 95% confidence interval [CI], 0.91-0.99; p = 0.023), OHE occurrence (sub-distribution hazard ratio, 0.92; 95% CI, 0.86-0.98; p = 0.013) and mortality (hazard ratio, 0.96; 95% CI, 0.93-0.99; p = 0.020) in patients with cirrhosis.

CONCLUSIONS

Vitamin D deficiency is highly prevalent and is associated with CHE, OHE, and mortality in patients with cirrhosis. Evaluation of vitamin D is essential to predict the outcomes of patients with cirrhosis.

A Mediterranean Diet-Based Metabolomic Score and Cognitive Decline in Older Adults: A Case-Control Analysis Nested within the Three-City Cohort Study

SCOPE

Evidence on the Mediterranean diet (MD) and age-related cognitive decline (CD) is still inconclusive partly due to self-reported dietary assessment. The aim of the current study is to develop an MD- metabolomic score (MDMS) and investigate its association with CD in community-dwelling older adults.

METHODS AND RESULTS

This study includes participants from the Three-City Study from the Bordeaux (n = 418) and Dijon (n = 422) cohorts who are free of dementia at baseline. Repeated measures of cognition over 12 years are collected. An MDMS is designed based on serum biomarkers related to MD key food groups and using a targeted metabolomics platform. Associations with CD are investigated through conditional logistic regression (matched on age, sex, and education level) in both sample sets. The MDMS is found to be inversely associated with CD (odds ratio [OR] [95% confidence interval (CI)] = 0.90 [0.80-1.00]; p = 0.048) in the Bordeaux (discovery) cohort. Results are comparable in the Dijon (validation) cohort, with a trend toward significance (OR [95% CI] = 0.91 [0.83-1.01]; p = 0.084).

CONCLUSIONS

A greater adherence to the MD, here assessed by a serum MDMS, is associated with lower odds of CD in older adults.

Eating Frequency, Timing, and Duration in Relation to Cognitive Performance and Alzheimer Disease Biomarkers in Adults

BACKGROUND

The potential association between temporal dimensions of eating and cognition/cognitive declines has been poorly investigated so far.

OBJECTIVES

The aim of this study was to examine relationships among eating frequency, timing and time window, and cognitive performance and novel Alzheimer disease (AD) biomarkers in cognitively healthy and mildly cognitively impaired middle-aged and older adults.

METHODS

Cross-sectional data were derived from the Aiginition Longitudinal Biomarker Investigation of Neurodegeneration (ALBION) cohort study, including people aged 40 y or older who have a positive family history of cognitive disorder or cognition-related concerns. Cognitive performance was assessed by a battery of neuropsychological tests. Amyloid β (Αβ42), a biomarker of AD-related pathology, was measured in cerebrospinal fluid. Eating frequency, timing, and the eating time window between the first and the last meal were estimated using time-related information recorded in four 24-h recalls.

RESULTS

Study participants had, on average, 5.3 ± 1.2 eating episodes per day, consumed at 8:20 ± 1.3 and 21:14 ± 1.3 h their first and their last eating episode, respectively, while their eating time window was 12.9 ± 1.6 h. Eating frequency, but not eating time window, was positively associated with global cognition, executive and language performance even after controlling for age, sex, education, BMI, and Mediterranean diet. Increasing eating frequency by 1 eating episode per day was associated with 0.169 higher global z-score. Furthermore, compared with ≤4, having 5-6 or >6 eating episodes per day was associated with better global and memory z-scores. Time of last eating episode was also positively associated with language performance. No associations were detected among eating frequency, timing and window, and AD pathology.

CONCLUSIONS

An eating pattern characterized by less frequent eating and/or by earlier times is present in individuals with worse cognitive performance. Our results shed light on the relevance of temporal eating patterns as potential early markers of behavioral or metabolic changes related to AD pathology.

Diet, Pace of Biological Aging, and Risk of Dementia in the Framingham Heart Study

OBJECTIVE

People who eat healthier diets are less likely to develop dementia, but the biological mechanism of this protection is not well understood. We tested the hypothesis that healthy diet protects against dementia because it slows the pace of biological aging.

METHODS

We analyzed Framingham Offspring Cohort data. We included participants ≥60 years-old, free of dementia and having dietary, epigenetic, and follow-up data. We assessed healthy diet as long-term adherence to the Mediterranean-Dash Intervention for Neurodegenerative Delay diet (MIND, over 4 visits spanning 1991-2008). We measured the pace of aging from blood DNA methylation data collected in 2005-2008 using the DunedinPACE epigenetic clock. Incident dementia and mortality were defined using study records compiled from 2005 to 2008 visit through 2018.

RESULTS

Of n = 1,644 included participants (mean age 69.6, 54% female), n = 140 developed dementia and n = 471 died over 14 years of follow-up. Greater MIND score was associated with slower DunedinPACE and reduced risks for dementia and mortality. Slower DunedinPACE was associated with reduced risks for dementia and mortality. In mediation analysis, slower DunedinPACE accounted for 27% of the diet-dementia association and 57% of the diet-mortality association.

INTERPRETATION

Findings suggest that slower pace of aging mediates part of the relationship of healthy diet with reduced dementia risk. Monitoring pace of aging may inform dementia prevention. However, a large fraction of the diet-dementia association remains unexplained and may reflect direct connections between diet and brain aging that do not overlap other organ systems. Investigation of brain-specific mechanisms in well-designed mediation studies is warranted. ANN NEUROL 2024;95:1069-1079.

Exploring the association between number of teeth, food intake, and cognitive function: A 9-year longitudinal study

OBJECTIVES

This study aimed to investigate the association between the number of teeth, food intake, and cognitive function in Japanese community-dwelling older adults.

METHODS

This 9-year longitudinal study included a total of 293 analyzable participants who participated in baseline and follow-up surveys. Dental status (number of teeth and periodontal pocket depth), dietary assessment using the brief-type self-administered diet history questionnaire, cognitive function, and the following confounding factors were evaluated: educational level, financial satisfaction, living situation, smoking and drinking habits, history of chronic diseases, apolipoprotein E-ε4 carrier, body mass index, handgrip strength, instrumental activities of daily living, and depressive symptomatology. The Japanese version of the Montreal Cognitive Assessment was used to evaluate cognitive function. A multinomial logistic regression analysis for the intake level of each food categorized into three groups (low, moderate, high), and a generalized estimating equation (GEE) for cognitive function over nine years were performed.

RESULTS

After controlling for confounding factors, the number of teeth was shown to be associated with the intake of green-yellow vegetables and meat. Furthermore, the GEE indicated that the lowest quartile of intake of green-yellow vegetables significantly associated with lower cognitive function (unstandardized regression coefficient [B] = -0.96, 95 % confidence interval [CI]: -1.72 to -0.20), and the lowest quartile of intake of meat significantly associated with lower cognitive function (B = -1.42, 95 % CI: -2.27 to -0.58).

CONCLUSIONS

The intake of green and yellow vegetables and meat, which is influenced by the number of teeth, was associated with cognitive function in Japanese community-dwelling older adults.

CLINICAL SIGNIFICANCE

There are few studies that have examined the association between oral health, food intake, and cognitive function. This 9-year longitudinal study suggests that it is important to maintain natural teeth to enable the functional means to consume green-yellow vegetables and meat, and thereby help maintain cognitive function.

The Association between cognitive impairment and anthropometric indices among the elderly: birjand longitudinal aging study

Background

The population of older adults has been consistently on the rise. We aimed to assess the possible relationship between cognitive decline and anthropometric indices in older adults, using data from the Birjand longitudinal aging study (BLAS).

Methods

In this cross-sectional research, the association between cognitive impairment as determined by two tests (Six Item Cognitive Impairment Test (6-CIT)) and (Mini-Mental State Examination (MMSE)) and anthropometric indices including waist circumference (WC), body mass index (BMI), waist to height ratio (WHtR), waist to hip ratio (WHR), body roundness index (BRI), and a body shape index (ABSI) were assessed among 1353 elderly ≥ 60 years old, participating in the BLAS cohort study (September 2018 to April 2019). Ordinal and binary logistic regression were used for analysis.

Results

According to the MMSE test, 58.3% of participants had cognitive impairment, while this frequency was 64.2% based on the 6-CIT test. A significant reverse association was observed between cognitive decline according to the 6-CIT test and BMI, WHR, and WC (P < 0.05). Cognitive impairment, according to MMSE, was inversely associated with WC and directly associated with WHtR and ABSI in the crude model, which disappeared after adjustment for confounders. BRI was not significantly related to any of the cognitive tests. According to BMI and WC, overweight and obesity could reduce the risk of cognitive impairment.

Conclusions

Overall, the result of this study showed that the risk of cognitive decline decreased among the elderly as BMI, WC, and WHR increased.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-024-01404-8.

Effects of vitamins and polyunsaturated fatty acids on cognitive function in older adults with mild cognitive impairment: a meta-analysis of randomized controlled trials

PURPOSE

Vitamins and polyunsaturated fatty acids (PUFAs) have been studied extensively as safe and manageable nutrient interventions for mild cognitive impairment (MCI). The purpose of the current meta-analysis was to examine the effects of vitamins and PUFAs on cognition and to compare the effects of single and multiple nutrient subgroups in patients with MCI.

METHODS

Randomized controlled trials (RCTs) written in English and Chinese were retrieved from eight databases, namely, PubMed, CENTRAL, Embase, CINAHL, Web of Science, SinoMed, CNKI, and Wanfang Data, from their respective dates of inception until 16 July 2023. The quality of the included studies was assessed using the Cochrane Risk of Bias Tool 2.0. Meta-analyses were performed to determine the standardized mean differences (SMDs) in global cognitive function, memory function, attention, visuospatial skills, executive function, and processing speed between the supplement and control groups using 95% confidence intervals (CI) and I2. Prospero registration number: CRD42021292360.

RESULTS

Sixteen RCTs that studied different types of vitamins and PUFAs were included. The meta-analysis revealed that vitamins affected global cognitive function (SMD = 0.58, 95% CI = [0.20, 0.96], P = 0.003), memory function (SMD = 2.55, 95% CI = [1.01, 4.09], P = 0.001), and attention (SMD = 3.14, 95% CI = [1.00, 5.28], P = 0.004) in patients with MCI, and PUFAs showed effects on memory function (SMD = 0.65, 95% CI = [0.32, 0.99], P < 0.001) and attention (SMD = 2.98, 95% CI = [2.11, 3.84], P < 0.001). Single vitamin B (folic acid [FA]: SMD = 1.21, 95% CI = [0.87, 1.55]) supplementation may be more effective than multiple nutrients (FA and vitamin B12: SMD = 0.71, 95% CI = [0.41, 1.01]; and FA combined with docosahexaenoic acid [DHA]: SMD = 0.58, 95% CI = [0.34, 0.83]) in global cognitive function.

CONCLUSIONS

FA, vitamin B6, vitamin B12, and vitamin D may improve global cognitive function, memory function, and attention in patients with MCI. Eicosapentaenoic acid (EPA) and DHA may improve memory function and attention. We also noted that FA may exert a greater effect than a vitamin B combination (FA and vitamin B12) or the combination of FA and DHA. However, because of the low evidence-based intensity, further trials are necessary to confirm these findings.

Environmental risk factors provoke new thinking for prevention and treatment of dementia with Lewy bodies

In recent years, environmental factors have received attention in the pathogenesis of neurodegenerative diseases. Other than genetic factors, the identification of environmental factors and modifiable risk factors may create opportunities to delay the onset or slow the progression of Lewy body disease. Researchers have made significant progress in understanding environmental and modifiable risk factors over the past 30 years. To date, despite the increasing number of articles assessing risk factors for Lewy body disease, few reviews have focused on their role in its onset. In this review, we reviewed the literature investigating the relationship between Lewy body disease and several environmental and other modifiable factors. We found that some air pollutants, exposure to some metals, and infection with some microorganisms may increase the risk of Lewy body disease. Coffee intake and the Mediterranean diet are protective factors. However, it is puzzling that low educational levels and smoking may have some protective effects. In addition, we proposed specific protocols for subsequent research directions on risk factors for neurodegenerative diseases and improved methods. By conducting additional case-control studies, we could explore the role of these factors in the etiopathogenesis of Lewy body disease, establishing a foundation for strategies aimed at preventing and reducing the onset and burden of the disease.

Effect of dietary patterns on mild cognitive impairment and dementia: a machine learning bibliometric and visualization analysis

Objective

As a spectrum of neurodegenerative conditions, dementia presents a significant challenge to worldwide health. Mild cognitive impairment (MCI) is recognized as the intermediate stage between normal cognitive functioning and dementia. Studies highlight the significant impact of dietary patterns on the management of MCI and dementia. Currently, comprehensive research on dietary patterns specific to MCI and dementia is limited, but bibliometric analysis offers a method to pinpoint essential research directions.

Methods

On November 18, 2023, a search was conducted in the Web of Science Core Collection (WoSCC) for publications on diet and MCI/dementia. Tools such as Rstudio, CiteSpace, and VOSviewer were employed to create a knowledge atlas. This atlas analyzed collaborations, reference co-citations, keyword patterns, and emerging trends.

Results

The search yielded 1,493 publications on diet and MCI/dementia, indicating a growing interest despite fluctuations. Contributions came from 70 countries/regions and 410 organizations across 456 journals. The USA and China led in publication numbers, with significant contributions from Columbia University and Harvard Medical School. Top authors include Scarmeas Nikolaos, Morris Martha Clare, and Samieri Cecilia. The Ketogenic, Mediterranean, and MIND diets emerged as key dietary patterns for cognitive decline prevention, highlighting the role of genetic factors, especially ApoE polymorphisms, in cognitive deterioration.

Conclusion

This study provides core countries, institutions, and authors in the field, and points out the development directions in the field. Future research directions in dietary for MCI and dementia will focus on: (1) the potential effects of the KD in alleviating oxidative stress and modulating gut microbiota in neurodegenerative diseases; (2) how diet influences cognitive health through patterns of ApoE and protein expression; (3) investigating the interactions between gut microbiota and brain function, known as the "gut-brain axis."

The association between adherence to the EAT-Lancet diet and cognitive ageing

BACKGROUND

The EAT-Lancet commission has proposed a dietary pattern that is both sustainable and healthy. However, the impact of this diet on cognition in older adults remains unexplored. Therefore, we examined the association between adherence to the EAT-Lancet diet and cognitive ageing.

METHODS

We used data from a previous intervention study involving cognitively healthy community-dwelling adults aged ≥65 years. Adherence to the EAT-Lancet diet was calculated using a recently published index and a 190-item food frequency questionnaire. Global and domain-specific cognitive functioning were assessed at baseline and after 2 years using a neuropsychological test battery. Multivariate-adjusted linear regression was conducted to examine associations between EAT-Lancet diet adherence and cognitive functioning (n = 630) and 2-year change (n = 302).

RESULTS

Greater adherence to the EAT-Lancet diet was associated with better global cognitive functioning (β per SD = 3.7 points [95% CI]: 0.04 [0.00, 0.08]) and slower rate of decline (β per SD [95% CI]: 0.05 [0.02, 0.08]). With respect to domain-specific functioning, beneficial associations were observed cross-sectionally for executive functioning (P < 0.01), and longitudinally for change in executive functioning (P < 0.01) and attention and working memory (P < 0.01). The degree of adherence to the EAT-Lancet was not associated with (changes in) information processing speed or episodic memory.

CONCLUSION

We demonstrated that greater adherence to the EAT-Lancet diet is associated with better global cognitive functioning and slower cognitive decline among cognitively healthy older adults. Further research is needed to confirm these findings and assess the potential benefits of the EAT-Lancet diet for the ageing population in a broader context.

Nutrition for dementia prevention: a state of the art update for clinicians

BACKGROUND AND OBJECTIVES

Dementia prevalence continues to rise. It is therefore essential to provide feasible and effective recommendations to encourage healthy brain ageing and reduce dementia risk across the population. Appropriate nutrition represents a potential strategy to mitigate dementia risk and could be recommended by clinicians as part of mid-life health checks and other health initiatives to reduce dementia prevalence. The purpose of this review is to provide a clinician-focused update on the current state of the knowledge on nutrition and dementia prevention.

METHODS

Narrative review.

RESULTS

Strong evidence exists to support the consumption of healthy, plant-based dietary patterns (e.g. Mediterranean, MIND or Nordic diet) for maintaining cognitive function and reducing dementia risk in later life and is supported by dementia prevention guideline from leading public health bodies (e.g. World Health Organization). Emerging evidence suggests potential cognitive benefits of consuming specific nutrients/foods (e.g. n-3 fatty acids or fish, flavonols and B-vitamins) and multi-nutrient compounds (e.g. Fortasyn Connect). Challenges and opportunities for integrating nutritional/dietary interventions for dementia prevention into clinical practice are explored in this review.

CONCLUSIONS

Appropriate nutrition represents an important factor to help facilitate healthy cognitive ageing and allay dementia risk. The information provided in this article can help clinicians provide informed opinions on appropriate nutritional strategies as part of mid-life Health Checks and other risk reduction initiatives.

Sexual and Gender Minority Status and Suicide Mortality: An Explainable Artificial Intelligence Analysis

Objectives: Suicide risk is elevated in lesbian, gay, bisexual, and transgender (LGBT) individuals. Limited data on LGBT status in healthcare systems hinder our understanding of this risk. This study used natural language processing to extract LGBT status and a deep neural network (DNN) to examine suicidal death risk factors among US Veterans. Methods: Data on 8.8 million veterans with visits between 2010 and 2017 was used. A case-control study was performed, and suicide death risk was analyzed by a DNN. Feature impacts and interactions on the outcome were evaluated. Results: The crude suicide mortality rate was higher in LGBT patients. However, after adjusting for over 200 risk and protective factors, known LGBT status was associated with reduced risk compared to LGBT-Unknown status. Among LGBT patients, black, female, married, and older Veterans have a higher risk, while Veterans of various religions have a lower risk. Conclusion: Our results suggest that disclosed LGBT status is not directly associated with an increase suicide death risk, however, other factors (e.g., depression and anxiety caused by stigma) are associated with suicide death risks.

A Genome-Wide Interaction Study of Erythrocyte ω-3 Polyunsaturated Fatty Acid Species and Memory in the Framingham Heart Study Offspring Cohort

BACKGROUND

Cognitive decline, and more specifically Alzheimer's disease, continues to increase in prevalence globally, with few, if any, adequate preventative approaches. Several tests of cognition are utilized in the diagnosis of cognitive decline that assess executive function, short- and long-term memory, cognitive flexibility, and speech and motor control. Recent studies have separately investigated the genetic component of both cognitive health, using these measures, and circulating fatty acids.

OBJECTIVES

We aimed to examine the potential moderating effect of main species of ω-3 polyunsaturated fatty acids (PUFAs) on an individual's genetically conferred risk of cognitive decline.

METHODS

The Offspring cohort from the Framingham Heart Study was cross-sectionally analyzed in this genome-wide interaction study (GWIS). Our sample included all individuals with red blood cell ω-3 PUFA, genetic, cognitive testing (via Trail Making Tests [TMTs]), and covariate data (N = 1620). We used linear mixed effects models to predict each of the 3 cognitive measures (TMT A, TMT B, and TMT D) by each ω-3 PUFA, single nucleotide polymorphism (SNP) (0, 1, or 2 minor alleles), ω-3 PUFA by SNP interaction term, and adjusting for sex, age, education, APOE ε4 genotype status, and kinship (relatedness).

RESULTS

Our analysis identified 31 unique SNPs from 24 genes reaching an exploratory significance threshold of 1×10-5. Fourteen of the 24 genes have been previously associated with the brain/cognition, and 5 genes have been previously associated with circulating lipids. Importantly, 8 of the genes we identified, DAB1, SORCS2, SERINC5, OSBPL3, CPA6, DLG2, MUC19, and RGMA, have been associated with both cognition and circulating lipids. We identified 22 unique SNPs for which individuals with the minor alleles benefit substantially from increased ω-3 fatty acid concentrations and 9 unique SNPs for which the common homozygote benefits.

CONCLUSIONS

In this GWIS of ω-3 PUFA species on cognitive outcomes, we identified 8 unique genes with plausible biology suggesting individuals with specific polymorphisms may have greater potential to benefit from increased ω-3 PUFA intake. Additional replication in prospective settings with more diverse samples is needed.

Consumption of Olive Oil and Diet Quality and Risk of Dementia-Related Death

Importance

Age-standardized dementia mortality rates are on the rise. Whether long-term consumption of olive oil and diet quality are associated with dementia-related death is unknown.

Objective

To examine the association of olive oil intake with the subsequent risk of dementia-related death and assess the joint association with diet quality and substitution for other fats.

Design, Setting, and Participants

This prospective cohort study examined data from the Nurses' Health Study (NHS; 1990-2018) and Health Professionals Follow-Up Study (HPFS; 1990-2018). The population included women from the NHS and men from the HPFS who were free of cardiovascular disease and cancer at baseline. Data were analyzed from May 2022 to July 2023.

Exposures

Olive oil intake was assessed every 4 years using a food frequency questionnaire and categorized as (1) never or less than once per month, (2) greater than 0 to less than or equal to 4.5 g/d, (3) greater than 4.5 g/d to less than or equal to 7 g/d, and (4) greater than 7 g/d. Diet quality was based on the Alternative Healthy Eating Index and Mediterranean Diet score.

Main Outcome and Measure

Dementia death was ascertained from death records. Multivariable Cox proportional hazards regressions were used to estimate hazard ratios (HRs) and 95% CIs adjusted for confounders including genetic, sociodemographic, and lifestyle factors.

Results

Of 92 383 participants, 60 582 (65.6%) were women and the mean (SD) age was 56.4 (8.0) years. During 28 years of follow-up (2 183 095 person-years), 4751 dementia-related deaths occurred. Individuals who were homozygous for the apolipoprotein ε4 (APOE ε4) allele were 5 to 9 times more likely to die with dementia. Consuming at least 7 g/d of olive oil was associated with a 28% lower risk of dementia-related death (adjusted pooled HR, 0.72 [95% CI, 0.64-0.81]) compared with never or rarely consuming olive oil (P for trend < .001); results were consistent after further adjustment for APOE ε4. No interaction by diet quality scores was found. In modeled substitution analyses, replacing 5 g/d of margarine and mayonnaise with the equivalent amount of olive oil was associated with an 8% (95% CI, 4%-12%) to 14% (95% CI, 7%-20%) lower risk of dementia mortality. Substitutions for other vegetable oils or butter were not significant.

Conclusions and Relevance

In US adults, higher olive oil intake was associated with a lower risk of dementia-related mortality, irrespective of diet quality. Beyond heart health, the findings extend the current dietary recommendations of choosing olive oil and other vegetable oils for cognitive-related health.

Systematic evaluation and meta-analysis of the effects of major dietary patterns on cognitive function in healthy adults

PURPOSE

Evidence shows diet promotes brain health. Combining foods and nutrients may have beneficial synergistic effects, but the effects on cognitive function interventions are inconsistent. So, a meta-analysis of RCTs was conducted to examine the specific effects on cognitive function.

METHODS

We searched four databases from creation to April 2023. Eligible randomized controlled trials were identified. A random-effects meta-analysis was used to combine standardized mean differences (SMD) (95% confidence intervals [CI]), and homogeneity tests for a variance were calculated.

RESULTS

A total of 19 studies involving 12,119 participants were included in this systematic review. The dietary intervention group had a positive effect on overall cognitive functioning compared to the control group (SMD = 0.14, 95% CI [0.08, 0.20], P < 0.00001). The dietary intervention improved executive function, processing speed and language skills (SMD = -0.10, 95% CI [-0.17,-0.04], P = 0.002, I2 = 0%), (SMD = -0.16, 95% CI [-0.23,-0.09], P < 0.00001, I2 = 0%), (SMD = 0.10, 95% CI [0.01, 0.20], P = 0.03, I2 = 0%). The dietary intervention had no effect on delayed memory and spatial ability (SMD = 0.04, 95% CI [-0.02, 0.09], P = 0.20, I2 = 0%), (SMD = 0.08, 95% CI [-0.01, 0.16], P = 0.08, I2 = 0%).

CONCLUSION

The Mediterranean diet, a diet with restricted caloric intake, a diet incorporating aerobic exercise, a low-carbohydrate diet, and a healthy lifestyle diet (increased intake of fruits and vegetables, and weight and blood pressure management) appear to have positive effects on cognitively healthy adults, as reflected in their overall cognitive, processing speed, executive, and language functions.

PROSPERO REGISTRATION NUMBER

CRD42023414704.

Association between Flavonoid Intake and Cognitive Executive Function among African American and White Adults in the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) Study

Healthy dietary patterns rich in flavonoids may benefit cognitive performance over time. Among socioeconomically disadvantaged groups, the association between flavonoid intake and measures of cognition is unclear. This study sought to identify associations between flavonoid intake and cognitive performance among Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study participants (n = 1947) across three study visits. Flavonoid intakes were assessed via two 24-h dietary recalls. Cognitive performance was assessed via the Trail Making Test (TMT)-A and TMT-B, which provide measures of attention and executive function, respectively. Mixed effects linear regression was used to model TMT scores over three study visits against visit 1 (v1) flavonoid intake, time (years from v1), and the interaction between v1 flavonoid intake and time, capturing both the cross-sectional association between flavonoid intake and time at v1 as well as the longitudinal association between v1 flavonoid intake and the change in TMT scores over time. Prior to adjustment, inverse cross-sectional associations at v1 were observed between (1) anthocyanidin intake and TMT-A scores for the overall sample and (2) total flavonoid, anthocyanidin, flavan-3-ol, flavone, and flavonol intake and TMT-B scores for the overall sample and among White adults. Only the association between anthocyanidin intake and TMT-B at v1 among White adults persisted after adjustment (for demographic characteristics such as age). One possible explanation for the few significant associations is universally low flavonoid intakes resulting from the consumption of an unhealthy dietary pattern.

Anti-Inflammatory Diet and Protein-Enriched Diet Can Reduce the Risk of Cognitive Impairment among Older Adults: A Nationwide Cross-Sectional Research

BACKGROUND

Cognitive impairment (CI) is a common mental health disorder among older adults, and dietary patterns have an impact on cognitive function. However, no systematic researches have constructed anti-inflammatory diet (AID) and protein-enriched diet (PED) to explore their association with CI among older adults in China.

METHODS

The data used in this study were obtained from the 2018 waves of the China Longitudinal Health and Longevity Survey (CLHLS). We construct AID, PED, and calculate scores for CI. We use binary logistic regression to explore the relationship between them, and use restrictive cubic splines to determine whether the relationships are non-linear. Subgroup analysis and sensitivity analysis were used to demonstrate the robustness of the results.

RESULTS

A total of 8692 participants (mean age is 83.53 years) were included in the analysis. We found that participants with a higher AID (OR = 0.789, 95% confidence interval: 0.740-0.842, p < 0.001) and PED (OR = 0.910, 95% confidence interval: 0.866-0.956, p < 0.001) score showed lower odds of suffering from CI. Besides, the relationship between the two dietary patterns and CI is linear, and the results of subgroup analysis and sensitivity analysis are also significant.

CONCLUSION

Higher intakes of AID and PED are associated with a lower risk of CI among older adults, which has important implications for future prevention and control of CI from a dietary and nutritional perspective.

The Influence of Social Dynamics on Biological Aging and the Health of Historically Marginalized Populations: A Biopsychosocial Model for Health Disparities

Historically marginalized populations are susceptible to social isolation resulting from their unique social dynamics; thus, they incur a higher risk of developing chronic diseases across the course of life. Research has suggested that the cumulative effect of aging trajectories per se, across the lifespan, determines later-in-life disease risks. Emerging evidence has shown the biopsychosocial effects of social stress and social support on one's wellbeing in terms of inflammation. Built upon previous multidisciplinary findings, here, we provide an overarching model that explains how the social dynamics of marginalized populations shape their rate of biological aging through the inflammatory process. Under the framework of social stress and social support theories, this model aims to facilitate our understanding of the biopsychosocial impacts of social dynamics on the wellbeing of historically marginalized individuals, with a special emphasis on biological aging. We leverage this model to advance our mechanistic understanding of the health disparity observed in historically marginalized populations and inform future remediation strategies.

Brain-Periphery Interactions in Huntington's Disease: Mediators and Lifestyle Interventions

Prominent pathological features of Huntington's disease (HD) are aggregations of mutated Huntingtin protein (mHtt) in the brain and neurodegeneration, which causes characteristic motor (such as chorea and dystonia) and non-motor symptoms. However, the numerous systemic and peripheral deficits in HD have gained increasing attention recently, since those factors likely modulate disease progression, including brain pathology. While whole-body metabolic abnormalities and organ-specific pathologies in HD have been relatively well described, the potential mediators of compromised inter-organ communication in HD have been insufficiently characterized. Therefore, we applied an exploratory literature search to identify such mediators. Unsurprisingly, dysregulation of inflammatory factors, circulating mHtt, and many other messenger molecules (hormones, lipids, RNAs) were found that suggest impaired inter-organ communication, including of the gut-brain and muscle-brain axis. Based on these findings, we aimed to assess the risks and potentials of lifestyle interventions that are thought to improve communication across these axes: dietary strategies and exercise. We conclude that appropriate lifestyle interventions have great potential to reduce symptoms and potentially modify disease progression (possibly via improving inter-organ signaling) in HD. However, impaired systemic metabolism and peripheral symptoms warrant particular care in the design of dietary and exercise programs for people with HD.

Fornix fractional anisotropy mediates the association between Mediterranean diet adherence and memory four years later in older adults without dementia

Here, we investigated whether fractional anisotropy (FA) of hippocampus-relevant white-matter tracts mediates the association between baseline Mediterranean diet adherence (MeDiAd) and verbal episodic memory over four years. Participants were healthy older adults with and without subjective cognitive decline and patients with amnestic mild cognitive impairment from the DELCODE cohort study (n = 376; age: 71.47 ± 6.09 years; 48.7 % female). MeDiAd and diffusion data were obtained at baseline. Verbal episodic memory was assessed at baseline and four yearly follow-ups. The associations between baseline MeDiAd and white matter, and verbal episodic memory's mean and rate of change over four years were tested with latent growth curve modeling. Baseline MeDiAd was associated with verbal episodic memory four years later (95 % confidence interval, CI [0.01, 0.32]) but not with its rate of change over this period. Baseline Fornix FA mediated - and, thus, explained - that association (95 % CI [0.002, 0.09]). Fornix FA may be an appropriate response biomarker of Mediterranean diet interventions on verbal memory in older adults.

Genetic risk for Alzheimer's disease and adherence to the Mediterranean diet: results from the HELIAD study

Obejctives: The aim of the current study was to investigate whether genetic risk factors may moderate the association between adherence to the Mediterranean diet and AD incidence.Mehtods: The sample was drawn from the HELIAD study, a longitudinal study with a follow-up interval of 3 years. In total 537 older adults without dementia or AD at baseline were included. Adherence to the Mediterranean diet was assessed at baseline and AD diagnosis was determined at both visits. A Polygenic Index for late onset AD (PGI-AD) was constructed. Cox proportional hazard models adjusted for age, sex, education, baseline Global cognition score and APOE e-4 genotype were employed to evaluate the association between PGI-AD and Mediterranean diet with AD incidence. Next, we examined the association between adherence to the Mediterranean diet and AD risk over time across participants stratified by low and high PGI-AD.Results: Twenty-eight participants developed AD at follow-up. In fully adjusted models both the PGI-AD and the adherence to the Mediterranean diet were associated with AD risk (p < 0.05 for both). In the low PGI-AD group, those with a low adherence had a 10-fold higher risk of developing AD per year of follow-up, than did the participants with a high adherence to the Mediterranean diet (p = 0.011), whereas no such association was found for participants in the high PGI-AD group.Discussion: The association of Mediterranean diet with AD risk is more prominent in the group of older adults with a low polygenic risk for developing AD. Our findings suggest that genetic risk factors should be taken into account when planning interventions aiming to improve cognitive health.

The Mediterranean-Dietary Approaches to Stop Hypertension Intervention for Neurodegenerative Delay (MIND) Diet for the Aging Brain: A Systematic Review

The Mediterranean-Dietary Approaches to Stop Hypertension Intervention for Neurodegenerative Delay (MIND) diet seems a promising approach to preserve brain function during aging. Previous systematic reviews have demonstrated benefits of the MIND diet for cognition and dementia, though an update is needed. Additionally, other outcomes relevant to brain aging have not been summarized. Therefore, this systematic review aims to give an up-to-date and complete overview on human studies that examined the MIND diet in relation to brain aging outcomes in adults aged ≥40 y. Ovid Medline, Web of Science core collection, and Scopus were searched up to July 25, 2023. Study quality was assessed using the Newcastle-Ottawa Scale and the Cochrane Risk-of-Bias tool. We included 40 articles, of which 32 were unique cohorts. Higher MIND diet adherence was protective of dementia in 7 of 10 cohorts. Additionally, positive associations were demonstrated in 3 of 4 cohorts for global cognition and 4 of 6 cohorts for episodic memory. The protective effects of the MIND diet on cognitive decline are less apparent, with only 2 of 7 longitudinal cohorts demonstrating positive associations for global decline and 1 of 6 for episodic memory decline. For other brain outcomes (domain-specific cognition, cognitive impairments, Parkinson's disease, brain volume, and pathology), results were mixed or only few studies had been performed. Many of the cohorts demonstrating protective associations were of North American origin, raising the question if the most favorable diet for healthy brain aging is population-dependent. In conclusion, this systematic review provides observational evidence for protective associations between the MIND diet and global cognition and dementia risk, but evidence for other brain outcomes remains mixed and/or limited. The MIND diet may be the preferred diet for healthy brain aging in North American populations, though evidence for other populations seems less conclusive. This review was registered at PROSPERO as CRD42022254625.

Impact of micronutrients and nutraceuticals on cognitive function and performance in Alzheimer's disease

Alzheimer's disease (AD) is a major global health problem today and is the most common form of dementia. AD is characterized by the formation of β-amyloid (Aβ) plaques and neurofibrillary clusters, leading to decreased brain acetylcholine levels in the brain. Another mechanism underlying the pathogenesis of AD is the abnormal phosphorylation of tau protein that accumulates at the level of neurofibrillary aggregates, and the areas most affected by this pathological process are usually the cholinergic neurons in cortical, subcortical, and hippocampal areas. These effects result in decreased cognitive function, brain atrophy, and neuronal death. Malnutrition and weight loss are the most frequent manifestations of AD, and these are also associated with greater cognitive decline. Several studies have confirmed that a balanced low-calorie diet and proper nutritional intake may be considered important factors in counteracting or slowing the progression of AD, whereas a high-fat or hypercholesterolemic diet predisposes to an increased risk of developing AD. Especially, fruits, vegetables, antioxidants, vitamins, polyunsaturated fatty acids, and micronutrients supplementation exert positive effects on aging-related changes in the brain due to their antioxidant, anti-inflammatory, and radical scavenging properties. The purpose of this review is to summarize some possible nutritional factors that may contribute to the progression or prevention of AD, understand the role that nutrition plays in the formation of Aβ plaques typical of this neurodegenerative disease, to identify some potential therapeutic strategies that may involve some natural compounds, in delaying the progression of the disease.

Effects of neighborhood built environment on cognitive function in older adults: a systematic review

BACKGROUND

In the background of an aging population, the risk of cognitive impairment in the older population is prominent. Exposure to complex neighborhood built environments may be beneficial to the cognitive health of older adults, and the purpose of this study was to systematically review the scientific evidence on the effects of neighborhood built environments on cognitive function in older adults.

METHODS

Keywords and references were searched in Web of Science, Pubmed, PsycINFO, and MEDLINE. Studies examining the relationship between the built environment and cognitive function in older adults were included. The neighborhood built environment as an independent variable was classified according to seven aspects: density, design, diversity, destination accessibility, public transportation distance, blue/green space, and built environment quality. The cognitive function as the dependent variable was classified according to overall cognitive function, domain-specific cognitive function, and incidence of dementia. The quality of the included literature was assessed using the National Institutes of Health's Observational Cohort and Cross-Sectional Study Quality Assessment Tool.

RESULTS

A total of 56 studies were included that met the inclusion criteria, including 31 cross-sectional studies, 23 longitudinal studies, 1 cross-sectional study design combined with a case-control design, and 1 longitudinal study design combined with a case-control design. Most of the studies reviewed indicate that the built environment factors that were positively associated with cognitive function in older adults were population density, street connectivity, walkability, number of public transportation stops around the residence, land use mix, neighborhood resources, green space, and quality of the neighborhood built environment. Built environment factors that were negatively associated with cognitive function in older adults were street integration, distance from residence to main road. The relationship between residential density, destination accessibility, and blue space with cognitive function in older adults needs to be further explored.

CONCLUSION

Preliminary evidence suggests an association between the neighborhood built environment and cognitive function in older adults. The causal relationship between the built environment and cognitive function can be further explored in the future using standardized and combined subjective and objective assessment methods, and longitudinal or quasi-experimental study designs. For public health interventions on the cognitive health of older adults, it is recommended that relevant authorities include the neighborhood built environment in their intervention programs.

Vitamin D3 improves iminodipropionitrile-induced tic-like behavior in rats through regulation of GDNF/c-Ret signaling activity

Children with chronic tic disorders (CTD), including Tourette syndrome (TS), have significantly reduced serum 25-hydroxyvitamin D [25(OH)D]. While vitamin D3 supplementation (VDS) may reduce tic symptoms in these children, its mechanism is unclear. The study aim was to investigate the effects and mechanisms of vitamin D deficiency (VDD) and VDS on TS model behavior. Forty 5-week-old male Sprague-Dawley rats were randomly divided into (n = 10 each): control, TS model, TS model with VDD (TS + VDD), or TS model with VDS (TS + VDS; two intramuscular injections of 20,000 IU/200 g) groups. The VDD model was diet-induced (0 IU vitamin D/kg); the TS model was iminodipropionitrile (IDPN)-induced. All groups were tested for behavior, serum and striatal 25(OH)D and dopamine (DA), mRNA expressions of vitamin D receptor (VDR), glial cell line-derived neurotrophic factor (GDNF), protooncogene tyrosine-protein kinase receptor Ret (c-Ret), and DA D1 (DRD1) and D2 (DRD2) receptor genes in the striatum. TS + VDD had higher behavior activity scores throughout, and higher total behavior score at day 21 compared with TS model. In contrast, day 21 TS + VDS stereotyped behavior scores and total scores were lower than TS model. The serum 25(OH)D in TS + VDD was < 20 ng/mL, and lower than control. Striatal DA of TS was lower than control. Compared with TS model, striatal DA of TS + VDD was lower, while in TS + VDS it was higher than TS model. Furthermore, mRNA expression of VDR, GDNF, and c-Ret genes decreased in TS model, and GDNF expression decreased more in TS + VDD, while TS + VDS had higher GDNF and c-Ret expressions. VDD aggravates, and VDS ameliorates tic-like behavior in an IDPN-induced model. VDS may upregulate GDNF/c-Ret signaling activity through VDR, reversing the striatal DA decrease and alleviating tic-like behavior.

Oleaginous Microbial Lipids' Potential in the Prevention and Treatment of Neurological Disorders

The products of oleaginous microbes, primarily lipids, have gained tremendous attention for their health benefits in food-based applications as supplements. However, this emerging biotechnology also offers a neuroprotective treatment/management potential for various diseases that are seldom discussed. Essential fatty acids, such as DHA, are known to make up the majority of brain phospholipid membranes and are integral to cognitive function, which forms an important defense against Alzheimer's disease. Omega-3 polyunsaturated fatty acids have also been shown to reduce recurrent epilepsy seizures and have been used in brain cancer therapies. The ratio of omega-3 to omega-6 PUFAs is essential in maintaining physiological function. Furthermore, lipids have also been employed as an effective vehicle to deliver drugs for the treatment of diseases. Lipid nanoparticle technology, used in pharmaceuticals and cosmeceuticals, has recently emerged as a biocompatible, biodegradable, low-toxicity, and high-stability means for drug delivery to address the drawbacks associated with traditional medicine delivery methods. This review aims to highlight the dual benefit that lipids offer in maintaining good health for disease prevention and in the treatment of neurological diseases.

Association of adherence to the Chinese version of the MIND diet with reduced cognitive decline in older Chinese individuals: Analysis of the Chinese Longitudinal Healthy Longevity Survey

BACKGROUND

Current evidence suggests that the Mediterranean-Dietary Approaches to Stop Hypertension (DASH) diet intervention for Neurodegenerative Delay (MIND) is associated with a reduced risk of cognitive impairment among North American and Oceanian populations. However, there has been limited exploration of whether this association extends to the Asian population. This study aimed to assess the correlation between the Chinese version of the MIND (cMIND) diet and cognitive impairment in older Chinese individuals.

METHODS

We utilized data from the 2008 wave of the Chinese Longitudinal Healthy Longevity Survey. Participants aged ≥65 years with normal cognitive function at baseline were enrolled. The cMIND diet score (cMINDDS) was calculated by assessing dietary patterns based on survey responses. The Chinese version of the Mini-Mental State Examination (MMSE) was employed to diagnose cognitive impairment in participants. We stratified the analysis by cMINDDS and conducted additional sensitivity analyses.

RESULTS

The cohort consisted of 6411 participants. Over a 3-year follow-up, 1165 (18.6%) individuals who initially had normal cognitive function developed cognitive impairment. A linear association was observed between cMINDDS and cognitive impairment. The increased cMINDDS was associated with a reduced risk of cognitive impairment (quartile 1 vs. quartile 4: the adjusted odds ratio [OR] = 0.77, 95% confidence interval [CI]: [0.60, 0.97], p trend = 0.023). Regarding food composition, higher consumption of fresh fruits and nuts was associated with a decreased risk of cognitive impairment (OR = 0.77, 95% CI: [0.66, 0.89] and OR = 0.70, 95% CI [0.58, 0.86], respectively).

CONCLUSIONS

Adherence to the cMIND diet was associated with lower risks of cognitive impairment in older Chinese individuals. The cMIND diet, based on the MIND dietary pattern, could serve as a preventive measure against cognitive impairment.

Dietary protein intake in midlife in relation to healthy aging - results from the prospective Nurses' Health Study cohort

BACKGROUND

Protein intake plays an important role in maintaining the health status of older adults. However, few epidemiologic studies examined midlife protein intake in relation to healthy aging.

OBJECTIVES

The objective of this study was to evaluate the long-term role of dietary protein intake in healthy aging among female participants in the prospective Nurses' Health Study (NHS) cohort.

METHODS

We included 48,762 NHS participants aged <60 y in 1984. Total protein, animal protein, dairy protein (a subset of animal protein), and plant protein were derived from validated food frequency questionnaires. Healthy aging was defined as being free from 11 major chronic diseases, having good mental health, and not having impairments in either cognitive or physical function, as assessed in the 2014 or 2016 NHS participant questionnaires. We used multivariate logistic regression adjusted for lifestyle, demographics, and health status to estimate the odds ratios (ORs) and 95% confidence intervals for protein intake in relation to healthy aging.

RESULTS

A total of 3721 (7.6%) NHS participants met our healthy aging definition. Protein intake was significantly associated with higher odds of healthy aging. The ORs (95% confidence intervals) per 3%-energy increment with healthy aging were 1.05 (1.01, 1.10) for total protein, 1.07 (1.02, 1.11) for animal protein, 1.14 (1.06, 1.23) for dairy protein, and 1.38 (1.24, 1.54) for plant protein. Plant protein was also associated with higher odds of absence of physical function limitations and good mental status. In substitution analyses, we observed significant positive associations for the isocaloric replacement of animal or dairy protein, carbohydrate, or fat with plant protein (ORs for healthy aging: 1.22-1.58 for 3% energy replacement with plant protein).

CONCLUSIONS

Dietary protein intake, especially plant protein, in midlife, is associated with higher odds of healthy aging and with several domains of positive health status in a large cohort of female nurses.

Two decades of research on the role of diet in Alzheimer's disease (2003-2023): a bibliometric and visual analysis based on CiteSpace

BACKGROUND

In recent years, the impact of diet on Alzheimer's disease (AD) as a modifiable lifestyle has attracted widespread attention. We aimed to elucidate the current research status, frontiers, and research trends regarding the role of diet in AD over the past two decades through CiteSpace.

METHODS

Studies related to AD and diet that were published from January 1, 2003, to June 30, 2023, were retrieved via the Web of Science Core Collection. We imported the study data into CiteSpace for visual analysis of countries, institutions, co-authors, and co-occurring keywords.

RESULTS

A total of 922 relevant studies were included in our analysis, which found Nikolaos Scarmeas was the most prolific author (13 studies, 1.41%). The results also indicated that USA and Columbia University were the country and institution with the highest number of publications, with 209 (22.67%) and 23 (2.49%), respectively. The keywords that had a burst in the past four years were neuroinflammation, AD, tau, association, and beta.

CONCLUSION

Talent exchange and regional cooperation are recommended in this study field. The results indicate that the effectiveness of various dietary patterns and mechanisms of dietary interventions using biomarkers and supplementation with refined nutrients will be the main research trends in the future.

Association between dietary diversity and cognitive impairment in community-dwelling older adults

AIM

The present study aimed to examine whether dietary diversity is associated with cognitive impairment, including mild cognitive impairment (MCI), in community-dwelling older Japanese adults.

METHODS

This cross-sectional study was carried out in a general community setting. MCI and global cognitive impairment (GCI) were assessed using the Mini-Mental State Examination and National Center for Geriatrics and Gerontology-Functional Assessment Tool, which are multicomponent neurocognitive tests that include memory attention, executive function and processing speed. Dietary diversity was assessed using the diet variety score. The diet variety score assessed the 1-week consumption frequency of 10 food groups, and either 0 or 1 point was allocated to each category based on the following responses: (i) "eat almost every day" (1 point); and (ii) "not eaten almost daily" (0 points). Older adults with a diet variety score of ≥3 points were defined as having high dietary diversity.

RESULTS

Data included 8987 older adults (mean age 73.9 ± 5.5 years; men 44.3%). The overall prevalences of MCI and GCI were 17.1% (n = 1538) and 8.4% (n = 753), respectively. The proportion of patients with a high dietary diversity was 69.9% (n = 6286). Multinomial logistic regression analysis revealed high dietary diversity was associated with MCI (OR 0.83, 95% CI 0.73-0.94) and GCI (OR 0.77, 95% CI 0.65-0.92) after adjusting for covariates.

CONCLUSIONS

This study had a large sample size of older Japanese adults, and showed that high dietary diversity was associated with a lower proportion of MCI and GCI among older adults. Geriatr Gerontol Int 2024; 24: 75-81.

High-Fat Diets in Animal Models of Alzheimer's Disease: How Can Eating Too Much Fat Increase Alzheimer's Disease Risk?

High dietary intake of saturated fatty acids is a suspected risk factor for neurodegenerative diseases, including Alzheimer's disease (AD). To decipher the causal link behind these associations, high-fat diets (HFD) have been repeatedly investigated in animal models. Preclinical studies allow full control over dietary composition, avoiding ethical concerns in clinical trials. The goal of the present article is to provide a narrative review of reports on HFD in animal models of AD. Eligibility criteria included mouse models of AD fed a HFD defined as > 35% of fat/weight and western diets containing > 1% cholesterol or > 15% sugar. MEDLINE and Embase databases were searched from 1946 to August 2022, and 32 preclinical studies were included in the review. HFD-induced obesity and metabolic disturbances such as insulin resistance and glucose intolerance have been replicated in most studies, but with methodological variability. Most studies have found an aggravating effect of HFD on brain Aβ pathology, whereas tau pathology has been much less studied, and results are more equivocal. While most reports show HFD-induced impairment on cognitive behavior, confounding factors may blur their interpretation. In summary, despite conflicting results, exposing rodents to diets highly enriched in saturated fat induces not only metabolic defects, but also cognitive impairment often accompanied by aggravated neuropathological markers, most notably Aβ burden. Although there are important variations between methods, particularly the lack of diet characterization, these studies collectively suggest that excessive intake of saturated fat should be avoided in order to lower the incidence of AD.

The role of natural flavonoids on neuroinflammation as a therapeutic target for Alzheimer's disease: a narrative review

Alzheimer's disease is a neurodegenerative disease that affects a large proportion of older adult people and is characterized by memory loss, progressive cognitive impairment, and various behavioral disturbances. Although the pathological mechanisms underlying Alzheimer's disease are complex and remain unclear, previous research has identified two widely accepted pathological characteristics: extracellular neuritic plaques containing amyloid beta peptide, and intracellular neurofibrillary tangles containing tau. Furthermore, research has revealed the significant role played by neuroinflammation over recent years. The inflammatory microenvironment mainly consists of microglia, astrocytes, the complement system, chemokines, cytokines, and reactive oxygen intermediates; collectively, these factors can promote the pathological process and aggravate the severity of Alzheimer's disease. Therefore, the development of new drugs that can target neuroinflammation will be a significant step forward for the treatment of Alzheimer's disease. Flavonoids are plant-derived secondary metabolites that possess various bioactivities. Previous research found that multiple natural flavonoids could exert satisfactory treatment effects on the neuroinflammation associated with Alzheimer's disease. In this review, we describe the pathogenesis and neuroinflammatory processes of Alzheimer's disease, and summarize the effects and mechanisms of 13 natural flavonoids (apigenin, luteolin, naringenin, quercetin, morin, kaempferol, fisetin, isoquercitrin, astragalin, rutin, icariin, mangiferin, and anthocyanin) derived from plants or medicinal herbs on neuroinflammation in Alzheimer's disease. As an important resource for the development of novel compounds for the treatment of critical diseases, it is essential that we focus on the exploitation of natural products. In particular, it is vital that we investigate the effects of flavonoids on the neuroinflammation associated with Alzheimer's disease in greater detail.

Multi-nutrient interventions and cognitive ageing: are we barking up the right tree?

As we continue to elucidate the mechanisms underlying age-related brain diseases, the reductionist strategy in nutrition–brain function research has focused on establishing the impact of individual foods. However, the biological processes connecting diet and cognition are complex. Therefore, consideration of a combination of nutritional compounds may be most efficacious. One barrier to establishing the efficacy of multi-nutrient interventions is that the area lacks an established set of evidence-based guidelines for studying their effect on brain health. This review is an output of the International Life Sciences Institute (ILSI) Europe. A multi-disciplinary expert group was assembled with the aim of developing a set of considerations to guide research into the effects of multi-nutrient combinations on brain functions. Consensus recommendations converged on six key issues that should be considered to advance research in this area: (1) establish working mechanisms of the combination and contributions of each individual compound; (2) validate the relevance of the mechanisms for the targeted human condition; (3) include current nutrient status, intake or dietary pattern as inclusion/exclusion criteria in the study design; (4) select a participant population that is clinically and biologically appropriate for all nutritional components of the combination; (5) consider a range of cognitive outcomes; (6) consider the limits of reductionism and the ‘gold standard’ randomised controlled trial. These guiding principles will enhance our understanding of the interactive/complementary activities of dietary components, thereby strengthening the evidence base for recommendations aimed at delaying cognitive decline.