Racial Differences in Dietary Relations to Cognitive Decline and Alzheimer's Disease Risk: Do We Know Enough?

A review of dairy food intake for improving health among black geriatrics in the US

The transition to older adulthood is generally marked by progressive declines in body composition, metabolism, cognitive function, and immunity. For socially disadvantaged geriatric populations such as Black Americans, this life stage may also include additional stressors, including dealing with discrimination, poor access to healthcare, and food insecurity. These types of chronic stressors are linked to a higher allostatic load, which is associated with accelerated biological aging, higher rates of adverse health outcomes, and an overall lower quality of life. Of the numerous factors involved in healthy aging, a growing body of research indicates that consuming a higher quality diet that is rich in fruits, vegetables, whole grains, protein foods, and dairy foods, is one of the most potent factors for helping to protect against age-related disease progression. Among the food groups listed above that are recommended by the 2020-2025 Dietary Guidelines for Americans dairy foods are unique in their ability to provide several of the essential nutrients (e.g., high-quality protein, calcium, potassium, vitamin B12, and vitamin D in fortified products) that are most often inadequately consumed by older Black Americans. However, dairy is the most inadequately consumed food group in the US, with older Black adults consuming fewer than half of the 3 daily recommended servings. Therefore, this review examines the current body of evidence exploring the links between dairy intake and age-related disease risk, with a special focus on health and disparities among older Black Americans. Overall, the evidence from most systematic reviews and/or meta-analyses focused on dairy intake and musculoskeletal health suggest that higher dairy intake across the life span, and especially from fermented and fortified products, is associated with better bone and muscle health outcomes in older adults. The evidence on dairy intake and neurocognitive and immune outcomes among older adults holds significant promise for potential benefits, but most of these results are sourced from individual studies or narrative reviews and are not currently corroborated in systematic reviews or meta-analyses. Additionally, most of the research on dairy intake and age-related disease risk has been performed in White populations and can only be extrapolated to Black populations. Nonetheless, older Black populations who do not meet the DGA recommended 3 servings of dairy per day due to lactose intolerance, restrictive dietary patterns, or for other reasons, are likely falling short of several of the nutritional requirements necessary to support healthy aging.

Mid-life adherence to the Dietary Approaches to Stop Hypertension (DASH) diet and late-life subjective cognitive complaints in women

INTRODUCTION

Evidence is limited on the role of mid-life Dietary Approaches to Stop Hypertension (DASH) diet in late-life subjective cognitive complaints (SCCs).

METHODS

We included 5116 women (mean age in 1985-1991: 46 years) from the New York University Women's Health Study. SCCs were assessed from 2018 to 2020 (mean age: 79 years) by a 6-item questionnaire.

RESULTS

Compared to women in the bottom quartile of the DASH scores, the odds ratio (OR) for having two or more SCCs was 0.83 (95% confidence interval: 0.70-0.99) for women in the top quartile of DASH scores at baseline (P for trend = 0.019). The association was similar with multiple imputation and inverse probability weighting to account for potential selection bias. The inverse association was stronger in women without a history of cancer (P for interaction = 0.003).

DISCUSSION

Greater adherence to the DASH diet in mid-life was associated with lower prevalence of late-life SCCs in women.

The association of spousal depressive symptoms and cognitive function among older adults: mediation and moderated mediation analyses

OBJECTIVES

To test whether contagious depressive symptoms mediate the association between spousal depressive symptoms (spousal-DS) and the other spouse's cognitive function, and test the moderated mediation of social activities engagement and sleep quality.

STUDY DESIGN

A total of 3,230 adults aged ≥60 and one of his/her close relatives were interviewed in 2016 in Xiamen, China.

METHODS

Cognitive function and depressive symptoms were measured by MoCA and GDS-15/CES-D-10, respectively. Social activities engagement and sleep quality were self-reported. Mediation and moderated mediation were tested by PROCESS macro with 5000 bootstrapping re-samples.

RESULT

Among all, 1,193 pairs were husband-wife with complete information and were included. The mean ages of older adults and their spouses were 68.35 ± 6.53 and 66.53 ± 7.91 years, respectively. The mean MoCA and GDS-15 scores for older adults were 22.21 ± 5.45 and 1.73 ± 2.17, respectively. The average score of CES-D-10 for spouses was 14.18 ± 4.77. Spousal-DS were associated with cognitive functions of older adults via the contagious depressive symptoms (indirect effect: -0.048, 95% confidence interval (CI): (-0.075, -0.028)). Such mediation can be buffered by attending social activities (interaction: -0.062, 95% CI: (-0.111, -0.013)) and improving sleep quality (interaction: -0.034, 95% CI: (-0.057, -0.012)).

CONCLUSION

Cognitive function of older adults was associated with his/her spouse's depressive symptoms, and the association was mediated by contagious depressive symptoms and moderated by social activities as well as sleep quality.

Pathways explaining racial/ethnic disparities in incident all-cause dementia among middle-aged US adults

INTRODUCTION

Racial disparities in dementia incidence exist, but less is known about their presence and drivers among middle-aged adults.

METHODS

We used time-to-event analysis among a sample of 4378 respondents (age 40-59 years at baseline) drawn from the third National Health and Nutrition Examination Surveys (NHANES III) with administrative linkage-spanning the years 1988-2014-to evaluate potential mediating pathways through socioeconomic status (SES), lifestyle, and health-related characteristics.

RESULTS

Compared with Non-Hispanic White (NHW) adults, Non-White adults had a higher incidence of AD-specific (hazard ratio [HR] = 2.05, 95% confidence interval [CI]: 1.21, 3.49) and all-cause dementia (HR = 2.01, 95% CI: 1.36, 2.98). Diet, smoking, and physical activity were among characteristics on the pathway between race/ethnicity, SES, and dementia, with health-mediating effects of smoking and physical activity on dementia risk.

DISCUSSION

We identified several pathways that may generate racial disparities in incident all-cause dementia among middle-aged adults. No direct effect of race was observed. More studies are needed to corroborate our findings in comparable populations.

Associations of lifestyle with physical, hearing, visual, and mental functional impairments among older adults: Findings from two prospective cohort studies

OBJECTIVE

To examine the associations between lifestyle habits and functional impairments among older adults.

METHODS

The study includes 20,545 women and 14,374 men aged 70 years or older at the time of the function assessment. Participants were from two prospective cohort studies: the Shanghai Women's Health Study (SWHS, enrollment from 1996 to 2000) and the Shanghai Men's Health Study (SMHS, enrollment from 2002 to 2006). Lifestyle information was collected at study enrollment and a healthy lifestyle score (HLS) was derived. Functional impairment information was collected at the follow-up survey conducted in 2012-2017. Logistic regression analyses were applied to estimate the associations of HLS with functional impairments.

RESULTS

The average age at lifestyle and functional impairment assessment was 62.3 (range: 49.9-70.9) and 77.7 (range: 70.0-89.4) for women and 67.5 (range: 55.1-74.9) and 77.4 (range: 70.0-88.6) for men. After a median follow-up of 14.4 years, we found that the HLS was inversely associated with overall severe functional impairment: odds ratio (95% confidence interval), 0.78(0.71-0.86) and individual severe functional impairment: 0.67(0.62-0.73) for independent walking, 0.85(0.77-0.94) for hearing/vision, 0.79(0.70-0.88) for memory, and 0.74(0.67-0.82) for decision-making impairment, comparing the highest with the lowest HLS categories. Such associations were similar among individuals with/without cardiometabolic diseases at baseline. The associations between each lifestyle factor and functional impairments differed.

CONCLUSION

A healthy lifestyle was associated with reduced odds of physical and mental impairment among older Chinese adults, emphasizing the importance of promoting and maintaining a healthy lifestyle to prevent or postpone age-related functional impairments.

Reflections on Mentorship From Scientists and Mentors in an Alzheimer's Disease Focused Research Training Program

This paper presents reflections on mentorship from scientists and mentors of the National Institute on Aging (NIA)-funded Carolina Center on Alzheimer's Disease and Minority Research (CCADMR). Using a network approach to mentoring, this program aims to increase the pipeline of underrepresented minority (URM) scientists studying Alzheimer's disease (AD) disparities. Six mentors and five scientists participated in interviews. Thematic analysis identified recurring themes; transcripts of mentors and scientists were compared. Most common thematic categories identified by mentors included experience interacting with scientists, goals as a mentor, recruitment of underrepresented minorities, scientists' challenges, and programmatic qualities. The most mentioned categories by scientists were challenges, seminars, working with mentors, career development, and project experience. The CCADMR will use findings to enhance the experience and training methods for future grant years. Results can benefit other training programs focused on aging and AD.

Development of an Advance Care Planning Portal-Based Tool for Community-Dwelling Persons Living With Cognitive Impairment: The ACPVoice Tool

Background: Patient portals can be an innovative and efficient way to engage patients in advance care planning (ACP). However, comprehension and judgment in older adults with cognitive impairment presents several barriers and challenges to engaging in new technology. Our objective was to develop an ACP portal-based tool (ACPVoice) for community-dwelling persons living with cognitive impairment (PLCI) by engaging end-users in the design process. Methods: Two rounds of cognitive interviews were conducted to identify and resolve cognitive issues related to comprehension, judgment, response, and to assess content validity. Purposive sampling was used with the goal of enrolling 15 different participants (five with mild cognitive impairment and five dyads (those with mild dementia and their care partner) in each round to assess respondents' understanding of questions related to advance care planning to be administered via the patient portal. Results: Twenty PLCI (mean age 78.4, 10 females [50%]) and ten care partners (mean age 60.9, 9 females [90%]) completed cognitive interviews between May 2021 and October 2021. The mean Mini-Mental State Examination score for PLCI was 25.6 (SD 2.6). Unclear wording and undefined vague and/or unfamiliar terms were the major issues identified. Revisions to item wording, response options, and instructions were made to improve question comprehension and response as well as navigational ease. Conclusion: Minor changes to the wording, format, and response options substantially improved respondents' ability to interpret the item content of the ACPVoice tool. Dissemination and implementation of the ACPVoice tool could help to engage community-dwelling PLCI in ACP discussions.

Type 2 Diabetes Independent of Glycemic Control is Associated With Cognitive Impairments: Findings From NHANES

Examine the association between glycemic control and cognition. Included subjects ≥60 years who participated in the 2013 to 2014 National Health and Nutrition Examination Survey and completed one of the followings: Consortium to Establish a Registry for Alzheimer's Disease Word List (CERAD-WL), Animal Fluency (AF), Digit Symbol Substitution Test (DSST), and CERAD-Delayed Recall (CERAD-DR). Stratified participants into: No type 2 diabetes (T2D; N = 557), Controlled T2D (N = 41), Uncontrolled T2D (N = 120), and Untreated T2D (N = 86). Multiple regression was used to examine the association between variables. After adjusting for demographics and cardiovascular risk factors, Uncontrolled T2D was associated with lower DSST (β = -3.164, p = .04), and Untreated T2D was associated with a trend for having lower CERAD-DR (β = -.496, p = .06) scores. T2D, independent of glycemic control, is associated with cognitive impairment and this relationship is influenced by modifiable and non-modifiable risk factors.

A healthy plant-based diet was associated with slower cognitive decline in African American older adults: a biracial community-based cohort

BACKGROUND

African American (AA) adults have about twice the risk of developing dementia compared with white adults. However, evidence on dietary modification in preventing cognitive decline from diverse populations focusing on AA adults is minimal.

OBJECTIVES

We aimed to evaluate the association between a plant-based diet and the rate of cognitive decline in a population-based sample of AA and white adults.

METHODS

This study consisted of 3337 participants from the Chicago Health and Aging Project (60% AA participants, 64% female). Plant-based diet quality was evaluated by the overall plant-based diet index (PDI), the healthful PDI (hPDI), and the unhealthful PDI (uPDI). Global cognition was assessed using a composite score of 4 individual tests of cognition. We used mixed models to examine the associations of PDI, hPDI, and uPDI with the rates of decline in global cognition, perceptual speed, and episodic memory. Models were adjusted for age, sex, presence of apoE e4 allele, lifestyle factors including education, cognitive activities, smoking status, calorie intake, risk factors for cardiovascular disease, time, and the interaction terms of time × each covariate.

RESULTS

AA and white participants had various dietary patterns. Higher hPDI was associated with a slower rate of decline in global cognition, perceptual speed, and episodic memory in AA participants but not white participants. AA study participants in the highest quintile of hPDI had significantly slower rates of global cognitive decline (β: 0.0183 ± 0.0086; P = 0.032), perceptual speed (β: 0.0179 ± 0.0088; P = 0.04), and episodic memory (β: 0.0163 ± 0.0118; P = 0.04) than individuals in the lowest quintile of hPDI. There were no associations of either PDI or uPDI with the rate of cognitive decline in either racial group.

CONCLUSIONS

A healthy plant-based diet was associated with a slower rate of decline in global cognition, perceptual speed, and episodic memory in AA adults.

Nutrition state of science and dementia prevention: recommendations of the Nutrition for Dementia Prevention Working Group

Observational studies suggest that nutritional factors have a potential cognitive benefit. However, systematic reviews of randomised trials of dietary and nutritional supplements have reported largely null effects on cognitive outcomes and have highlighted study inconsistencies and other limitations. In this Personal View, the Nutrition for Dementia Prevention Working Group presents what we consider to be limitations in the existing nutrition clinical trials for dementia prevention. On the basis of this evidence, we propose recommendations for incorporating dietary patterns and the use of genetic, and nutrition assessment tools, biomarkers, and novel clinical trial designs to guide future trial developments. Nutrition-based research has unique challenges that could require testing both more personalised interventions in targeted risk subgroups, identified by nutritional and other biomarkers, and large-scale and pragmatic study designs for more generalisable public health interventions across diverse populations.

Association between healthy eating index-2015 and various cognitive domains in US adults aged 60 years or older: the National Health and Nutrition Examination Survey (NHANES) 2011-2014

BACKGROUND

Diet, as a modifiable factor, plays an important role in cognitive function. However, the association between adherence to the 2015-2020 Dietary Guidelines for Americans (DGA), measured by Healthy Eating Index (HEI)-2015, and cognitive function remains unclear. This study aims to explore whether HEI-2015 is associated with various cognitive domains and whether such association is modified by age, gender, or ethnicity in the US adults aged 60 years or older using data from the National Health and Nutrition Examination Survey (NHANES) 2011-2014.

METHODS

HEI-2015 scores were calculated from 24-h dietary recall interviews. Cognitive function was evaluated by Digit Symbol Substitution Test (DSST, a measure of processing speed), Animal Fluency Test (AFT, a measure of executive function), a subtest from Consortium to Establish a Registry for Alzheimer's disease (CERAD, a measure of memory), and a composite-z score calculated by summing z scores of individual tests. The associations between HEI-2015 scores and cognitive performance were explored using multiple linear regression models.

RESULTS

A total of 2450 participants aged 60 years or older were included. Participants with higher HEI-2015 scores were more likely to have higher DSST, AFT as well as composite-z scores (P<0.05). Significant interaction effects were identified between HEI-2015 and ethnicity in specific cognitive domains (P_interaction<0.05). Among HEI-2015 components, higher intakes of whole fruits and seafood and plant protein were associated with better cognitive performance (P<0.05).

CONCLUSION

Higher adherence to DGA is associated with better cognitive performance, especially regarding processing speed and executive function among the US adults aged 60 years or older.

Vascular smooth muscle cell dysfunction contribute to neuroinflammation and Tau hyperphosphorylation in Alzheimer disease

Despite the emerging evidence implying early vascular contributions to neurodegenerative syndromes, the role of vascular smooth muscle cells (VSMCs) in the pathogenesis of Alzheimer disease (AD) is still not well understood. Herein, we show that VSMCs in brains of patients with AD and animal models of the disease are deficient in multiple VSMC contractile markers which correlated with Tau accumulation in brain arterioles. Ex vivo and in vitro experiments demonstrated that VSMCs undergo dramatic phenotypic transitions under AD-like conditions, adopting pro-inflammatory phenotypes. Notably, these changes coincided with Tau hyperphosphorylation at residues Y18, T205, and S262. We also observed that VSMC dysfunction occurred in an age-dependent manner and that expression of Sm22α protein was inversely correlated with CD68 and Tau expression in brain arterioles of the 3xTg-AD and 5xFAD mice. Together, these findings further support the contribution of dysfunctional VSMCs in AD pathogenesis and nominate VSMCs as a potential therapeutic target in AD.

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Loss of VSMC contractile phenotypes correlates with Tau accumulation in brain arterioles

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VSMC dysfunction promotes the hyperphosphorylation of Tau protein at multiple residues

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VSMC dysfunction occurs in an age-dependent manner in brain arterioles of patients with AD

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Vascular smooth muscle cell is a promising therapeutic target in AD

Latent Profile Analysis of Cognition in a Non-Demented Diverse Cohort: A Focus on Modifiable Cardiovascular and Lifestyle Factors

BACKGROUND

Cognitively-defined subgroups are well-documented within neurodegeneration.

OBJECTIVE

We examined such profiles in diverse non-demented older adults and considered how resulting subgroups relate to modifiable factors associated with neurodegeneration.

METHODS

121 non-demented (MMSE = 28.62) diverse (46%non-Latino Black, 40%non-Latino White, 15%Latino) community-dwelling adults (age = 67.7 years) completed cognitive, cardiovascular, physical activity, and diet evaluations. Latent profile analyses (LPA) employed six cognitive scores (letter fluency, letter-number sequencing, confrontational naming, 'animal' fluency, list-learning delayed recall, and recognition discriminability) to characterize cognitively-defined subgroups. Differences between resulting subgroups on cardiovascular (composite scores of overall health; specific health components including fasting blood levels) and lifestyle (sedentary behavior; moderate-to-vigorous physical activity; Mediterranean diet consumption) factors were examined using ANCOVAs adjusting for relevant confounders.

RESULTS

Based on sample means across cognitive scores, LPA resulted in the following cognitive subgroups: 1) high-average cognition, 55%non-Latino White and 64%female participants; 2) average cognition, 58%non-Latino Black and 68%male participants; 3) lower memory, 58%non-Latino Black participants; and 4) lower executive functioning, 70%Latinos. The high-average subgroup reported significantly higher Mediterranean diet consumption than the average subgroup (p = 0.001). The lower executive functioning group had higher fasting glucose and hemoglobin A1c than all other subgroups (p-values<0.001).

CONCLUSION

LPA revealed two average subgroups reflecting level differences in cognition previously reported between non-Latino White and Black adults, and two lower cognition subgroups in domains similar to those documented in neurodegeneration. These subgroups, and their differences, suggest the importance of considering social determinants of health in cognitive aging and modifiable risk.

A Critical Review of the Study of Neuroprotective Diets to Reduce Cognitive Decline

Alzheimer’s disease (AD) and other dementias are now the seventh leading cause of death in the world and are projected to affect 115.4 million people by 2050. Delaying the onset of AD by just five years is estimated to reduce the cost and prevalence of the disease by half. There is no cure for AD nor any drug therapies to halt its progression once the disease begins. Lifestyle choices including diet are being seen as a viable complementary therapy to reduce cognitive decline, the hallmark of AD. Mediterranean, DASH (Dietary Approaches to Stop Hypertension), and MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) diets have biological mechanisms supporting their potential neuroprotective benefits, but the findings of study outcomes about these benefits have been inconsistent. This paper analyzed five Randomized Clinical Trials (RCTs) (from 2000 to 2021) and 27 observational studies (from 2010 to 2021) focused on the link between cognitive health and the Mediterranean/DASH/MIND diets to identify gaps and challenges that could lead to inconsistent results. These include a lack of accuracy in assessing food intake, multiple dietary pattern scoring systems, a shifting metric among studies focused on the Mediterranean diet, a lack of standards in the tools used to assess cognitive decline, and studies that were underpowered or had follow-up periods too short to detect cognitive change. Insights from these gaps and challenges are summarized in recommendations for future RCTs, including both pragmatic and explanatory RCTs.