An evidence-based method for examining and reporting cognitive processes in nutrition research

Alignment of Consumers' Expected Brain Benefits from Food and Supplements with Measurable Cognitive Performance Tests

Consumers often cite cognitive improvements as reasons for making dietary changes or using dietary supplements, a motivation that if leveraged could greatly enhance public health. However, rarely is it considered whether standardized cognitive tests that are used in nutrition research are aligned to outcomes of interest to the consumer. This knowledge gap presents a challenge to the scientific substantiation of nutrition-based cognitive health benefits. Here we combined focus group transcript review using reflexive thematic analysis and a multidisciplinary expert panel exercise to evaluate the applicability of cognitive performance tools/tasks for substantiating the specific cognitive benefits articulated by consumers with the objectives to (1) understand how consumers comprehend the potential benefits of nutrition for brain health, and (2) determine the alignment between consumers desired brain benefits and validated tests and tools. We derived a 'Consumer Taxonomy of Cognitive and Affective Health in Nutrition Research' which describes the cognitive and affective structure from the consumers perspective. Experts agreed that validated tests exist for some consumer benefits including focused attention, sustained attention, episodic memory, energy levels, and anxiety. Prospective memory, flow, and presence represented novel benefits that require the development and validation of new tests and tools. Closing the gap between science and consumers and fostering co-creative approaches to nutrition research are critical to the development of products and dietary recommendations that support realizable cognitive benefits that benefit public health.

Diet patterns associated with cognitive decline: methods to harmonize data from European and US cohort studies

The impact of dietary intake on cognitive outcomes and dementia prevention is a topic of increasing interest. Meta-analyses of observational studies, mostly conducted within US and European populations, have reported benefits of healthy diet patterns on cognitive performance, but results from individual studies have been inconsistent. These inconsistencies are likely due to the diverse methodology used in studies, including different diet and cognitive function assessment instruments, follow-up periods, and analytical methods, which make drawing conclusions relevant to dietary guidance challenging. The objective of this project is to describe a protocol to conduct a retrospective harmonization study on dietary intake and cognitive health using data from European and US studies. The recommendations resulting from the project can be used to support evidence-based synthesis for future iterations of the Dietary Guidelines for Americans or other population-based dietary guidance. Additionally, this study will serve as a harmonization guide for future research on the relationship between diet patterns and cognition. The approach outlined ultimately aims to optimize resources and expedite research efforts for dementia prevention.

Exposure to greenspace and bluespace and cognitive functioning in children - A systematic review

BACKGROUND

The field of greenspace and bluespace research in relation to cognitive outcomes is rapidly growing. Several systematic reviews have already been published on this topic but none of them are specific to cognitive outcomes in the entire age range of children. Moreover, only a few of them have examined the effects of bluespace in addition to greenspace. Also, theses reviews are focused either only on observational studies or experimental studies. Our systematic review focuses on cognitive outcomes in relation to greenspace and bluespace in children and adolescents aged 0-18; it captures both observational and experimental studies. Cognitive outcomes are presented according to an evidence-based taxonomy of human cognitive abilities: the Cattell-Horn-Carroll (CHC) theory.

METHODS

We conducted searches in the PubMed and PsychInfo databases, from their inception dates to 17 December 2021. We used three-text terms related to outcome, exposure, and population as well as MeSH terms for outcome and population. Further, the reference lists and existing reviews were searched ("snowball" search) until 21 April 2022 to detect additional studies. For the results reporting, we followed the updated guidelines of the Preferred Reporting Items for Systematic reviews and Meta Analyses (PRISMA). We included observational and experimental studies on greenspace or bluespace exposure in relation to cognitive functioning, published in English, German, or Polish. Two reviewers independently checked study eligibility and extracted data. Two reviewers evaluated the risk of bias according to the Office of Health Assessment and Translation (OHAT) tool. At all stages, discrepancies between the two reviewers were solved via discussion with a third reviewer.

RESULTS

Records identified from PubMed (n = 2030) and PsycINFO (n = 1168) were deduplicated and screened. Twenty one reports were first selected. The "snowball" search revealed 16 additional reports. Altogether, 39 studies (17 experimental and 22 observational) published in 37 reports were qualified. The data extraction showed that the methodology used in the studies was heterogenous and the findings were inconsistent. The majority of the studies investigated attentional functioning, which we subdivided into two categories according to the CHC theory: attentional control and reaction and decision speed (12 studies) and attentional control and processing speed (10 studies). Eleven studies investigated working memory and/or short-term memory that we categorized as CHC working memory capacity. Nine studies investigated intellectual functioning, which we categorized as CHC general ability, fluid reasoning, and comprehension-knowledge. Two studies investigated visual-spatial skills, which we categorized as CHC visual processing and psychomotor speed. One study measured parent-reported attention; two studies examined early childhood/cognitive development; three studies examined decision-making and self-regulation, which can be categorized as several CHC theory abilities.

DISCUSSION

The heterogeneity of the included studies does not permit clear conclusions for our review. In accordance with previous systematic reviews, greenspace and bluespace were not more strongly related to a particular domain of cognitive functioning than other cognitive domains, and no effects of age or type of exposure assessment on the association between nature and cognition were detected. Further research is needed, including state-of-the-art of assessment of cognitive outcomes and diverse exposure assessment methods within both observational and experimental approaches. Expertise will be required in several domains, such as environmental epidemiology, cognitive psychology, and neuropsychology. Systematic review registration number (INPLASY): 202220018.

Pyrethroid and Chlorpyrifos Pesticide Exposure, General Intellectual Abilities, and Executive Functions of School Children from Montevideo, Uruguay

Children's developing brains are susceptible to pesticides. Less is known about the effect of exposure to chlorpyrifos and pyrethroids on executive functions (EF). We measured urinary 3,5,6-trichloro-2-pyridinol (TCPy), a metabolite of chlorpyrifos, and urinary 3-phenoxybenzoic acid (3-PBA), a general, nonspecific metabolite of pyrethroids in first-grade children from Montevideo, Uruguay (n = 241, age 80.6 ± 6.4 months, 58.1% boys). EFs were assessed with the Intra-dimensional/Extra-dimensional shift (IED), Spatial Span (SSP), and Stockings of Cambridge (SOC) tests from the Cambridge Neuropsychological Test Automated (CANTAB) Battery. General intellectual ability (GIA) was assessed using the Woodcock-Muñoz Cognitive battery. Median (range) urinary TCPy and 3-PBA levels were 16.7 (1.9, 356.9) ng/mg of creatinine and 3.3 (0.3, 110.6) ng/mg of creatinine, respectively. In multivariable generalized linear models, urinary TCPy was inversely associated with postdimensional errors on the IED task β [95% CI]: -0.11 [-0.17, -0.06]. Urinary 3-PBA was inversely associated with the total number of trials -0.07 [-0.10, -0.04], and the total number of errors -0.12 [-0.18, -0.07] on the IED task. When TCPy and 3-PBA were modeled together, the associations did not differ from single-metabolite models. We found no evidence of effect modification by blood lead level (BLL). Pesticide exposure may affect EF performance in urban children.

Perspective: Advancing dietary guidance for cognitive health - focus on solutions to harmonization of test selection, implementation, and evaluation

This perspective paper is a product of a workshop of experts convened by Institute for the Advancement of Food and Nutrition Sciences (IAFNS), a non-profit organization that brings together scientists from government, academia, and industry to catalyze science relevant to food and nutrition. An expert group was convened in March 2022 to discuss the current issues surrounding cognitive task selection in nutrition research, with a focus on solutions towards informing dietary guidance for cognitive health, to address a gap identified in the 2020 US DGAC report, specifically the "considerable variation in testing methods used, [and] inconsistent validity and reliability of cognitive testing methods" (p.31). To address this issue, we firstly undertook an umbrella review of relevant reviews already undertaken; these indicate agreement on some of the issues that affect heterogeneity in task selection, and on many of the fundamental principles underlying selection of cognitive outcome measures. However, resolving the points of disagreement is critical to ensuring meaningful impact on the issue of heterogeneity in task selection; these issues hamper evaluation of existing data for informing dietary guidance. This summary of the literature is therefore followed by the expert group's perspective in the form of a discussion of potential solutions to these challenges, with the aim of building on the work of previous reviews in the area and advancing dietary guidance for cognitive health. STATEMENT OF SIGNIFICANCE: Despite several high-quality reviews in this field over the last two decades, there has been little in the way of substantive change in the methods being used to conduct studies, hampering harmonization of the evidence and thus, its utility for informing dietary guidance. The present paper comprehensively updates the field by firstly providing an umbrella review of the published reviews, followed by the IAFNS expert group's perspective on how to move the field forward by addressing the challenges and areas of disagreement in the existing reviews. REGISTERED ON PROSPERO: CRD42022348106. Data described in the manuscript, code book, and analytic code will be made publicly and freely available without restriction at doi.org/10.17605/OSF.IO/XRZCK.

The treatment of sleep dysfunction to improve cognitive function: A meta-analysis of randomized controlled trials

OBJECTIVE

This meta-analysis of randomized controlled trials (RCTs) evaluates if treating sleep disturbances improves cognitive function over at least 12 weeks.

METHODS

Multiple data sources were searched until November 1, 2021. RCTs were included if they examined the effect of an intervention (behavioral or medical) on sleep and cognition in an adult sample with sleep disturbances and had an intervention duration and follow-up of at least 12 weeks. Two independent reviewers located 3784 studies; 16 satisfied the inclusion criteria. Primary outcomes included the broad cognitive domains of visual processing, short-term memory, long-term storage and retrieval, processing speed, and reaction time.

RESULTS

Most trials were conducted in participants with obstructive sleep apnea (OSA; N = 13); the most studied intervention was continuous positive airway pressure (CPAP; N = 10). All RCTs were 12 months in duration or less. The estimates of mean pooled effects were not indicative of significant treatment effect for any primary outcome. Although the interventions reduced daytime sleepiness (Hedge's g, 0.51; 95% confidence interval, 0.29-0.74; p < 0.01), this did not lead to cognitive enhancement.

CONCLUSIONS

Overall, there was insufficient evidence to suggest that treating sleep dysfunction can improve cognition. Further studies with longer follow-up duration and supporting biomarkers are needed.

Dietary Flavonoids and Human Cognition: A Meta-Analysis

Improving cognition is important in all age groups, from performance in school examinations to prevention of cognitive decline in later life. Dietary polyphenols, in particular flavonoids, have been examined for their benefits to cognitive outcomes. This meta-analysis evaluates the effects of dietary flavonoids on cognition across the lifespan. In January 2020 databases were searched for randomized controlled trials investigating flavonoid effects on human cognition. Eighty studies, comprising 5519 participants, were included in the final meta-analysis. The global analysis indicates dietary flavonoids induced significant benefit to cognitive performance (g = 0.148, p < 0.001), with subgroup analyses revealing that cocoa (g = 0.224, p = 0.036), ginkgo (g = 0.187, p ≤ 0.001), and berries (g = 0.149, p = 0.009) yielded the most notable improvements. Significant benefits were observed from chronic studies, in middle-aged and older adults, and with low and medium doses. The domains of long-term memory, processing speed, and mood showed sensitivity to flavonoid intervention. This meta-analysis provides evidence for the positive effects of flavonoids on cognition and highlights several moderating factors. Flavonoid-based dietary interventions therefore potentially offer a highly accessible, safe, and cost-effective treatment to help tackle the burden of cognitive decline.

The Moo'D Study: protocol for a randomised controlled trial of A2 beta-casein only versus conventional dairy products in women with low mood

Background

Beta-casein is a major protein in cow’s milk, of which A1 and A2 are the most frequent variants. Recent evidence implicates A1 beta-casein consumption in mechanisms that are of potential importance to mental health, yet its possible effects on psychological endpoints remains unknown. The primary aim of the study is to evaluate the comparative effects of consumption of dairy products containing A2 beta-casein versus conventional dairy (i.e. containing both A1 and A2 beta-casein) on symptoms of psychological distress in women with low mood.

Methods

‘The Moo’D Study’ is a 16-week, superiority, 1:1 parallel group, triple-blinded, randomised controlled trial. Ninety women with low mood (Patient Health Questionnaire score ≥ 5) will be randomised to consume either A2 beta-casein only or conventional dairy products. The primary outcome, symptoms of psychological distress, will be measured by the 21-item Depression, Anxiety and Stress Scale. Secondary outcomes will include symptoms of depression, anxiety and stress, severity of low mood, cognition, gut microbiota composition, gut symptomatology, markers of immune function, gut inflammation, systemic metabolites, endothelial integrity and oxidative stress, body composition, perceived wellbeing, sleep, quality of life, resource use and cost-effectiveness.

Discussion

This study will advance our understanding of the possible impact of milk proteins on psychological distress in women as well as elucidate mechanisms underpinning any association. Given dairy products form a substantial component of traditional and Western diets, the implications of these findings are likely to be of clinical and public health importance.

Trial registration

The trial protocol has been prospectively registered with the Australia and New Zealand Clinical Trials Registry, ACTRN12618002023235. Registered on 17 December 2018.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05812-6.

Is there a relationship between low-grade systemic inflammation and cognition in healthy people aged 60-75 years?

Although inflammation has been associated with cognitive impairment in dementia, less is known about its role in the cognition of middle to older aged healthy people. This study utilised baseline data from the Australian Research Council Longevity Intervention (ARCLI) trial to investigate the relationship between markers of systemic inflammation (TNF-α, IL-6, IL-1β, INF-γ, IL-2, IL-4, IL-10 and hsCRP) and cognitive function in 286 healthy volunteers aged 60-75 years. We assessed cognitive functioning across domains including attention, speed of memory, working memory and episodic memory using the Cognitive Drug Research test battery. Only IFN-γ was related to cognitive function, being associated with greater odds of having low continuity of attention (log2 IFN-γ OR, 1.46; 95 % CI, 1.18-1.85). The relationship between episodic memory, speed of memory and inflammation varied with BMI. In high BMI participants, increased inflammation was associated with worse cognitive function, while this association was reversed in those with low BMI. Outside of the influence of IFN-γ on attention, low-grade systemic inflammation was not robustly associated with cognitive function in this sample of middle to older aged healthy people. Further research is required to understand the role of BMI in the intersection of inflammation and cognitive function.

Effect of resveratrol supplementation on cognitive performance and mood in adults: a systematic literature review and meta-analysis of randomized controlled trials

Context

The aim of this systematic review was to evaluate clinical trial data regarding the effect of resveratrol supplementation on cognitive performance and mood in populations that are healthy and in the clinical setting.

Data Sources

Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic literature review of randomized controlled trials was conducted.

Data Extraction

A meta-analysis was also conducted to determine treatment effect on the following cognitive domains and mental processes: processing speed, number facility, memory, and mood. Risk of bias was assessed using the Cochrane Collaboration Risk of Bias tool. Quality of the body of evidence was assessed by evidence for each outcome related to cognitive function for which data was assessed using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE).

Results

Ten studies were included. Three studies found resveratrol supplementation significantly improved some measures of cognitive performance, 2 reported mixed findings, and 5 found no effect. When data were pooled, resveratrol supplementation had a significant effect on delayed recognition (standardized mean difference [SMD], 0.39; 95% confidence interval [CI], 0.08-0.70; I2 = 0%; P = 0.01; n = 3 studies; n = 166 participants) and negative mood (SMD, -0.18; 95%CI, -0.31 to -0.05; I2 = 0%; P = 0.006; n = 3 studies; n = 163 participants). Included studies generally had low risk of bias and were of moderate or high quality.

Conclusions

The results of this review indicate that resveratrol supplementation might improve select measures of cognitive performance; however, the current literature is inconsistent and limited.

The microbiome and cognitive aging: a review of mechanisms

Gut microbiota plays an intrinsic role in communication between the gut and the brain and is capable of influencing the host brain by producing neurotransmitters and neurotrophins, the modulation of inflammatory processes amongst other key mechanisms. Increased age is also associated with changes in these key biological processes and impairments in a range of cognitive processes. We hypothesise several mechanisms in which gut microbiota may modulate changes in cognitive function with age. In this review, we discuss issues related to the measurement of cognition in the elderly and in particular outline a standardised model of cognition that could be utilised to better understand cognitive outcomes in future studies examining the relationship between gut microbiota and cognition in the elderly. We then review biological processes such as oxidative stress and inflammation which are related to cognitive changes with age and which are also influenced by our gut microbiota. Finally, we outline other potential mechanisms by which the gut microbiota may influence cognition.

Evidence and mechanisms for statin-induced cognitive decline

INTRODUCTION

Statin drugs have become the most highly prescribed drugs for cardiovascular disease. However, there is disagreement as to the existence of adverse effects of statin administration on cognitive function. Therefore, it is important to better understand the effects of statins on cognition and possible mechanisms of these effects. Areas covered: We analyzed relevant studies of the relationship between cognitive performance and statin and usage. We included articles published between 2018 and 1992. We identified three randomized trials, one observational study and 66 case reports that provided credible evidence of statin-induced cognitive impairment. We also identified seven randomized trials and two observational studies reporting no significant evidence of statin-induced cognitive impairment. Expert opinion: We found methodological differences that may have contributed to the divergence of these results. Evaluation of all these studies indicated that statin-associated cognitive decline is a real entity. Likely mechanisms to explain the adverse effects include 1. Reduction of synthesis of coenzyme Q10 with consequent increasing oxidative stress and reduction of cerebral energy production; 2. Depletion of central nervous system myelin by inhibition of cholesterol synthesis. We conclude that statin-induced cognitive decline does exist, needs to be better recognized and requires more studies of prevention and treatment.

Latent subgroups of cognitive performance in lead- and manganese-exposed Uruguayan children: Examining behavioral signatures

OBJECTIVES

Lead (Pb) and manganese (Mn) are confirmed neurotoxins but it is unclear to what extent low-level exposure produces a unique behavioral signature. The objective of this study was to investigate latent cognitive profiles among children (6-8 years) from Montevideo, Uruguay co-exposed to these metals.

METHOD

Among 345 children, blood Pb and hair Mn were measured using atomic absorption spectroscopy and ICP-MS, respectively. Sixteen measures, reflecting multiple domains of cognitive functioning were gathered: (1) three tests from Cambridge Neuropsychological Test Automated Battery (CANTAB): Intra-Extra Dimensional Shift (IED), Spatial Span (SSP) and Stockings of Cambridge (SOC), (2) ten tasks from Woodcock-Muñoz Achievement Battery, Revised (WM): Visual-Motor Integration, Verbal Comprehension (Vocabulary, Synonyms, Antonyms, Analogies), Visual-Auditory Comprehension, Concept Formation, Visual Spatial Thinking, Number Inversion and Spatial Relations, (3) Bender Gestalt task, and (4) Weschler block design task. Scores were modeled using latent profile analysis (LPA). Association between blood Pb and hair Mn on performance profiles was assessed using ordinal regression, controlling for confounders. An interaction between Pb and Mn was tested.

RESULTS

Mean ± SD of blood Pb was 4.1 ± 2.1 μg/dL and 35% of children had blood Pb ≥ 5 μg/dL. Median [5%, 95%] hair Mn level was 0.8 [0.3, 4.1] ppb. Three latent cognitive performance profiles were identified: high (n = 46, 13%), average (n = 209, 61%) and low (n = 90, 26%). Each one-unit increase in blood Pb was associated with a 28% greater likelihood of belonging to a poorer-performing profile. The association was non-linear, with the effect of Pb on profile membership strongest at lower levels of exposure. There was no meaningful interaction between Pb and Mn.

CONCLUSIONS

A behavioral signature for low-level Pb & Mn exposure was not identified, but the likelihood of membership in low-performing profile was higher at lowest levels of blood Pb. There was no effect measure modification between Pb and Mn. Future research should address how complex environments created by chemical exposures and the social context relate to cognitive performance in young children.

An overview and critique of the Test of Visual Perception Skills - fourth edition (TVPS-4)

Introduction

The Test of Visual Perception Skills - fourth edition (TVPS-4) is an updated version of the Test of Visual Perception Skills - third edition (TVPS-3). The TVPS-4 is a standardized assessment of motor-free visual perception skills for individuals aged 5-21 years. Test norms were derived from a normative sample that reflected the United States population.

Method

The present paper outlines and appraises the reliability and validity of the TVPS-4. Measurement properties of the TVPS-4 were critiqued using the Quality Criteria for Health Status Questionnaires (QCHSQ) and the Consensus-based Standards for the Selection of Health Measurement Instruments (COSMIN) checklist with 4-point rating scale.

Results

The TVPS-4 manual reports details of reasonable levels and types of overall reliability and validity. The QCHSQ and COSMIN checklist reviews suggested that further research is needed in relation to the TVPS-4's measurement error, reproducibility, internal consistency and cross-cultural validity.

Conclusion

The TVPS-4 is an in-depth assessment that can be used to identify areas of impairment and assist with goal setting and intervention planning. The impact of the TVPS-4 on occupational therapy practice is also considered. Future research could investigate the cross-cultural validity of the TVPS-4 so that it can be used in other countries with confidence.

Reduced inattention and hyperactivity and improved cognition after marine oil extract (PCSO-524®) supplementation in children and adolescents with clinical and subclinical symptoms of attention-deficit hyperactivity disorder (ADHD): a randomised, double-blind, placebo-controlled trial

INTRODUCTION

This study investigated the effects of a marine oil extract (PCSO-524®) on inattention, hyperactivity, mood and cognition in children and adolescents. PCSO-524® is a standardised lipid extract of the New Zealand green-lipped mussel and is an inflammatory modulator that inhibits the 5'-lipoxygenase and cyclooxygenase pathways and decreases concentrations of the pro-inflammatory arachidonic acid (AA).

METHODS

PCSO-524® or a matched placebo was administered for 14 weeks to 144 participants (123 males/21 females; mean age 8.7 years) with high hyperactivity and inattention in a randomised, double-blind, placebo-controlled study. The primary outcome was the Conners Parent Rating Scale assessing parental reports of behavioural problems. Secondary outcomes assessed changes in cognition and mood.

RESULTS

The results of the present study did not support the hypothesis that PCSO-524® improves parental reports of hyperactivity, inattention and impulsivity in children ages 6 to 14 years over placebo. Repeated measures ANOVA on post hoc subsample analysis indicated significant improvements in hyperactivity (p = 0.04), attention (p = 0.02), learning (p = 0.05) and probability of ADHD (p = 0.04) with a medium to large average effect size (d = 0.65) in those children who did not meet criteria for combined hyperactivity and inattention. Furthermore, significant improvements in the PCSO-524® group were indicated in a whole sample repeated measures ANCOVA on recognition memory between baseline and week 8 over placebo (p = 0.02, d = 0.56); this difference was not sustained at week 14.

CONCLUSIONS

The results presented indicate that PCSO-524® may be beneficial in reducing levels of hyperactivity and inattention in a population of children with clinical and subclinical symptoms of ADHD.

Improving Cognition in the Elderly With Nutritional Supplements

With increasing life expectancies in most Western populations, the number of people experiencing age-associated cognitive impairment is increasing. Research is needed to identify factors that may help the elderly maintain or even improve cognitive function in the face of advancing age. This review evaluates whether dietary supplementation with natural pharmaceuticals can be used as a means to improve cognitive function or limit cognitive decline. The evidence surrounding popular supplements such as Ginkgo biloba, fish oils, Bacopa monnieri, polyphenol extracts, and vitamins is reviewed briefly. Potential mechanisms of action are also highlighted. This review also discusses challenges surrounding cognitive testing in psychopharmacological research, highlighting discrepancies between the domains of human cognition as described by contemporary models and as measured in clinical trials.