Dietary Inflammatory Potential and the Risk of Neurodegenerative Diseases in Adults

The Association Between Diets With High Inflammatory Potential and Sleep Quality and Its Parameters: A Systematic Review

CONTEXT

Dietary components or its overall properties can influence an individual's sleep status.

OBJECTIVE

The aim for this study was to critically search, appraise, and synthesize research evidence on the association between dietary inflammatory index (DII) and sleep quality and its parameters.

DATA SOURCES

Original published studies on adults were obtained from the PubMed, SCOPUS, ScienceDirect, Cochrane Library, and Google Scholar databases.

DATA EXTRACTION

The search was conducted without date limitation until April 2023. Duplicated and irrelevant investigations were screened out, and the results of the remaining articles were descriptively summarized, then critically appraised and analyzed. Possible mechanistic pathways regarding diet, systemic inflammation, and sleep status were discussed.

DATA ANALYSIS

Of the 102 studies searched, 23 articles (n = 4 cohort studies, 18 cross-sectional studies, and 1 intervention study) were included in the final review. The association between DII and sleep status was investigated subjectively in 21 studies and objectively in 6 studies. The main studied sleep outcomes were sleep quality, duration, latency, efficiency, apnea, disturbances, the use of sleeping medications, daytime dysfunctions, wakefulness after sleep onset, and rapid eye movement.

CONCLUSIONS

According to most of the evidence, DII may not be related to overall sleep quality, sleep duration, latency, efficiency, and the use of sleeping medications. The evidence of positive association was greater between a high DII score (pro-inflammatory diet) with daytime dysfunctions, wakefulness after sleep onset, and sleep apnea. There is insufficient evidence to make any conclusion regarding sleep disturbances and rapid eye movement.

In Vitro and In Vivo Supplementation with Curcumin Promotes Hippocampal Neuronal Synapses Development in Rats by Inhibiting GSK-3β and Activating β-catenin

The human fetal thyroid gland is not capable of producing thyroid hormones independently until 20 weeks of gestation, and if maternal thyroid hormone synthesis is inadequate in early pregnancy, fetal brain and nerve development may be affected by maternal hypothyroidism. Curcumin, which is isolated from turmeric (Curcuma longa), has been shown to be effective in repairing neurological disorders and is effective in relieving nerve damage when consumed over a long period of time. In this experiment, we investigated the effect of curcumin supplementation on synaptic development of rat hippocampal neurons. A cell model of oxidative damage and a young rat model of hypothyroidism were constructed, and model cells and rats were treated with triiodothyronine (T3), tetraiodothyronine (T4), and curcumin, respectively. Damage of nerve cells and animal brain tissues was examined, and the effect of curcumin in alleviating the blocked neurodevelopment was investigated. Further modulation of GSK-3β/β-catenin was performed to investigate the mechanism of action of curcumin. Ultimately, we found that T3-, T4-, and curcumin-treated model cells and young rats had increased numbers of synapses and good neurodevelopment. At the same time, we found that curcumin inhibited the production of GSK-3β and Axin to activate β-catenin. The inhibition of β-catenin weakened the therapeutic effect of curcumin, and the differences between the indicators and the model group disappeared. Both cellular and animal experiments supported that curcumin effectively alleviated the oxidative cell damage caused by thyroxine deficiency and activated the synaptogenic ability of nerve synapses by inhibiting GSK-3β and protecting β-catenin activity.

Brain functional and structural changes in diabetic children. How can intellectual development be optimized in type 1 diabetes?

The neuropsychological functioning of people with type 1 diabetes (T1D) is of key importance to the effectiveness of the therapy, which, in its complexity, requires a great deal of knowledge, attention, and commitment. Intellectual limitations make it difficult to achieve the optimal metabolic balance, and a lack of this alignment can contribute to the further deterioration of cognitive functions. The aim of this study was to provide a narrative review of the current state of knowledge regarding the influence of diabetes on brain structure and functions during childhood and also to present possible actions to optimize intellectual development in children with T1D. Scopus, PubMed, and Web of Science databases were searched for relevant literature using selected keywords. The results were summarized using a narrative synthesis. Disturbances in glucose metabolism during childhood may have a lasting negative effect on the development of the brain and related cognitive functions. To optimize intellectual development in children with diabetes, it is essential to prevent disorders of the central nervous system by maintaining peri-normal glycemic levels. Based on the performed literature review, it seems necessary to take additional actions, including repeated neuropsychological evaluation with early detection of any cognitive dysfunctions, followed by the development of individual management strategies and the training of appropriate skills, together with complex, multidirectional environmental support.

Association between dietary inflammatory index and mental disorders using multilevel modeling with GLIMMIX

Introduction

The Dietary Inflammatory Index (DII) is a composite nutritional index that has gained significant attention in the past decade due to its association with physical and mental well-being. To accurately assess the precise effects of DII on health outcomes, the effects of nutrients and foods need to be adjusted. This study aimed to investigate the association between DII and mental disorders (depression, anxiety, and stress) using multilevel modeling to minimize the bias of the previous methods.

Methods

This cross-sectional analytical study was conducted using data from the initial phase of the Tehran University of Medical Sciences Employees' Cohort Study (TEC). Nutritional information was obtained through a dish-based semi-quantitative food frequency questionnaire (DFQ), while psychological data were collected using the depression, anxiety and stress scale (DASS-42). The acquired data were analyzed using multilevel modeling in three levels (foods, nutrients, and DII, respectively) through GLIMMIX in the SAS software.

Results

A total of 3,501 individuals participated in this study. The results of the multilevel model demonstrated a significant statistical association between DII and mental disorders after adjusting for baseline characteristics, nutrients and foods. For each unit increase in DII, the mean scores for stress, anxiety, and depression increased by 3.55, 4.26, and 3.02, respectively (p < 0.001).

Conclusion

Based on the multilevel model's findings, it is recommended to minimize the use of pro-inflammatory nutrients and foods to increase the mental health. Multilevel data analysis has also been recommended in nutritional studies involving nested data to obtain more accurate and plausible estimates.

No Effect of Calorie Restriction or Dietary Patterns on Spatial Working Memory During a 2-Year Intervention: A Secondary Analysis of the CALERIE Trial

BACKGROUND

The effect of calorie restriction (CR) on cognitive function is not well understood, and the impact of the dietary patterns consumed during CR has not been investigated.

OBJECTIVES

We analyzed the combined association of CR and dietary quality with spatial working memory (SWM) in healthy adults without obesity.

METHODS

The Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) trial was a 2-y, multisite clinical trial. This trial was registered at clinicaltrials.gov as NCT00427193. Participants were randomized to a 25% reduction in EI (n = 143) or an ad libitum Control (n = 76). The Dietary Inflammatory Index (DII) and the Healthy Eating Index (HEI) captured dietary quality, with a lower DII and higher HEI score indicating a healthier diet. The Cambridge Neuropsychological Test Automated Battery battery was used to assess SWM. Longitudinal associations between each dietary pattern index and SWM for CR and Control were assessed by multivariable negative binomial models that included baseline, 12-mo, and 24-mo visits.

RESULTS

Participants were aged 38.1 ± 7.2 y with a BMI of 25.1 ± 1.7 kg/m². A total of 70% of the participants were female. Baseline mean DII and HEI scores were -0.15 (range: -3.77, 4.21) and 59.1 (24.1, 91.0) and did not differ between groups. Improvements in DII and HEI were significantly different between CR and Control over 2 y (both P-interaction = 0.001). In longitudinal analyses, there was no association of either index with SWM. Furthermore, though within-group improvements in SWM were observed at 12 mo, there was no statistically significant difference between CR (SWM errors: 9.0; 95% CI: 1.9, 41.6) and Control (11.7; 95% CI: 2.6, 53.5; P > 0.99), holding DII constant. Comparable results were observed at 24 mo and for the HEI.

CONCLUSIONS

Dietary quality during CR was not associated with measures of SWM over 2 y in healthy adults without obesity. These results suggest that, in healthy populations, dietary patterns and CR may have a limited impact on working memory. Further research is required to understand the concurrent effect of these nutritional strategies.

Association between dietary inflammatory index and cognitive impairment: A meta-analysis

Aims

Cognitive impairment is an increasingly urgent global public health challenge. Dietary Inflammatory Index (DII) is a literature-derived score that links diet to inflammation. The relationship between DII and cognitive impairment remains controversial. Therefore, our study aimed to analysis the role of DII on the risk of cognitive impairment by meta-analysis.

Methods

PubMed, Cochrane Library, MEDLINE, Web of Science and EMBASE databases were searched up to July 2022. Newcastle-Ottawa scale (NOS) and Joanna Briggs Institute (JBI) Checklist were performed to estimate the quality of studies.

Results

Nine observational studies with 19,379 subjects were included. Our study found that higher DII could elevate the risk of cognitive impairment (OR = 1.46, 95%CI = 1.26, 1.69). Meanwhile, the OR of cognitive impairment was 1.49 (95%CI = 1.21, 1.83) for cross-sectional studies and 1.42 (95%CI = 1.12, 1.79) for cohort studies, respectively.

Conclusion

Our meta-analysis indicated that higher DII (indicating a more pro-inflammatory diet) is related to increased risk of cognitive impairment.

Dietary Patterns and Nonmotor Symptoms in Parkinson's Disease: A Cross-Sectional Analysis

OBJECTIVE

Evidence-based treatment for nonmotor symptoms in Parkinson's disease (PD) is limited. Lifestyle-based improvements including dietary changes may be a potential management strategy. The intent of this research was to investigate the extent to which 3 dietary indices (Mediterranean-DASH Diet Intervention for Neurodegenerative Delay [MIND], Dietary Inflammation Index [DII], and Healthy Diet Indicator [HDI-2020]) are associated with overall and individual nonmotor symptom severity among individuals with PD.

METHOD

An exploratory cross-sectional analysis of dietary (food frequency questionnaire) and clinical data was undertaken, including measures of overall nonmotor symptom severity, such as fatigue, depression, anxiety, apathy, sleep problems, daytime sleepiness, and cognitive impairment. The relationship between each dietary score and symptom outcome was assessed by linear regression for continuous variables and through general linear model analysis for tertiles of dietary adherence.

RESULTS

None of the dietary indices significantly predicted the total nonmotor symptom severity score. The HDI predicted a significant decrease in fatigue scores as measured by the NeuroQoL fatigue item (standardized β = -.19, p = 0.022), after adjusting for age, sex, energy intake, years since diagnosis, physical activity level, education, and smoking. Self-reported depression symptoms reduced by .17 (standardized β) for each unit increase in HDI score (p = 0.035), after controlling for age, gender, energy intake, and years since diagnosis. No other significant associations were evident between dietary scores and any other nonmotor symptoms.

CONCLUSIONS

Our results indicate that fatigue and depression in PD may be modified by diet; however, more research is needed using a larger sample to replicate these findings.

Supplemental data for this article is available online at https://doi.org/10.1080/07315724.2022.2056544 .

Dietary Inflammatory Index score and prodromal Parkinson's disease incidence: The HELIAD study

AIM

The aim of the present study was to investigate the association of the inflammatory potential of diet with prodromal Parkinson's disease (pPD) probability and incidence among community-dwelling older individuals without clinical features of parkinsonism at baseline.

METHODS

The sample consisted of 1,030 participants 65 years old or older, drawn from a population-based cohort study of older adults in Greece (Hellenic Longitudinal Investigation of Aging and Diet - HELIAD). We calculated pPD probability, according to International Parkinson and Movement Disorder Society research criteria. Dietary Inflammatory Index (DII) was used to measure the dietary inflammatory potential, with higher index score reflecting a more pro-inflammatory diet. Associations of baseline DII with pPD probability cross-sectionally, and with possible/probable pPD incidence (pPD probability ≥30%) during the follow-up period, were examined via general linear models and generalized estimating equations, respectively.

RESULTS

Cross-sectionally, one unit increase of DII score[DII (min, max) = -5.83, 6.01]was associated with 4.9% increased pPD probability [β=0.049, 95%CI (0.025-0.090), p<0.001]. Prospectively, 62 participants developed pPD during 3.1±0.9 (mean±SD) years of follow-up. One unit increase in DII was associated with 20.3% increased risk for developing pPD [RR=1.203, 95%CI (1.070-1.351), p=0.002]. Participants in the highest tertile of DII score were 2.6 times more likely to develop pPD [β=2.594, 95%CI (1.332-5.050), p=0.005], compared to those in the lowest tertile.

CONCLUSION

More pro-inflammatory diet was related with higher pPD probability and pPD incidence (pPD probability ≥30%) in a community-dwelling older adult population. Further studies are needed to confirm these findings.

COVCOG 1: Factors Predicting Physical, Neurological and Cognitive Symptoms in Long COVID in a Community Sample. A First Publication From the COVID and Cognition Study

Since its first emergence in December 2019, coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has evolved into a global pandemic. Whilst often considered a respiratory disease, a large proportion of COVID-19 patients report neurological symptoms, and there is accumulating evidence for neural damage in some individuals, with recent studies suggesting loss of gray matter in multiple regions, particularly in the left hemisphere. There are a number of mechanisms by which COVID-19 infection may lead to neurological symptoms and structural and functional changes in the brain, and it is reasonable to expect that many of these may translate into cognitive problems. Indeed, cognitive problems are one of the most commonly reported symptoms in those experiencing "Long COVID"-the chronic illness following COVID-19 infection that affects between 10 and 25% of patients. The COVID and Cognition Study is a part cross-sectional, part longitudinal, study documenting and aiming to understand the cognitive problems in Long COVID. In this first paper from the study, we document the characteristics of our sample of 181 individuals who had experienced COVID-19 infection, and 185 who had not. We explore which factors may be predictive of ongoing symptoms and their severity, as well as conducting an in-depth analysis of symptom profiles. Finally, we explore which factors predict the presence and severity of cognitive symptoms, both throughout the ongoing illness and at the time of testing. The main finding from this first analysis is that that severity of initial illness is a significant predictor of the presence and severity of ongoing symptoms, and that some symptoms during the initial illness-particularly limb weakness-may be more common in those that have more severe ongoing symptoms. Symptom profiles can be well described in terms of 5 or 6 factors, reflecting the variety of this highly heterogenous condition experienced by the individual. Specifically, we found that neurological/psychiatric and fatigue/mixed symptoms during the initial illness, and that neurological, gastrointestinal, and cardiopulmonary/fatigue symptoms during the ongoing illness, predicted experience of cognitive symptoms.

The Interplay of the Unfolded Protein Response in Neurodegenerative Diseases: A Therapeutic Role of Curcumin

Abnormal accumulation of misfolded proteins in the endoplasmic reticulum and their aggregation causes inflammation and endoplasmic reticulum stress. This promotes accumulation of toxic proteins in the body tissues especially brain leading to manifestation of neurodegenerative diseases. The studies suggest that deregulation of proteostasis, particularly aberrant unfolded protein response (UPR) signaling, may be a common morbific process in the development of neurodegeneration. Curcumin, the mixture of low molecular weight polyphenolic compounds from turmeric, Curcuma longa has shown promising response to prevents many diseases including current global severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and neurodegenerative disorders. The UPR which correlates positively with neurodegenerative disorders were found affected by curcumin. In this review, we examine the evidence from many model systems illustrating how curcumin interacts with UPR and slows down the development of various neurodegenerative disorders (ND), e.g., Alzheimer's and Parkinson's diseases. The recent global increase in ND patients indicates that researchers and practitioners will need to develop a new pharmacological drug or treatment to manage and cure these neurodegenerative diseases.

Assessing the (anti)-inflammatory potential of diets

PURPOSE OF REVIEW

It is accepted that several chronic diseases are associated with inflammation. Dietary habits and the consumption of certain nutrients have been shown to influence inflammation, reflected by inflammatory cytokines. In this narrative review, we discuss currently developed tools to assess the inflammatory potential of diets and compare them with established tools.

RECENT FINDINGS

Four new indices were recently developed. The Inflammatory Score of the Diet is a modified version of the established Dietary Inflammatory Index. The novel Empirical Dietary Inflammatory Index works without previous dietary intake assessment and the Anti-Inflammatory Diet Index was specifically developed in a northern European population. The Dietary and Lifestyle Inflammation Scores addresses additional confounders. The informative value of dietary indices relies on the accuracy and completeness of dietary intake assessment.

SUMMARY

Dietary inflammatory indices are important tools to assess, compare and validate the inflammatory potential of diets across populations without the need for biomarker assessments. They allow to investigate associations between an (anti)-inflammatory diet with disease risk and course. Although the Dietary Inflammatory Index remains the most used index worldwide, currently developed indices allow more flexibility, have a different focus or simplify assessment. Additional foods, that were recently shown to modulate inflammation, but are not (fully) considered yet, may deserve more attention in the future.

The Role of Inflammatory Diet and Vitamin D on the Link between Periodontitis and Cognitive Function: A Mediation Analysis in Older Adults

Patients suffering from periodontitis are at a higher risk of developing cognitive dysfunction. However, the mediation effect of an inflammatory diet and serum vitamin D levels in this link is unclear. In total, 2062 participants aged 60 years or older with complete periodontal diagnosis and cognitive tests from the National Health and Nutrition Examination Survey (NHANES) 2011-2012 and 2013-2014 were enrolled. The Consortium to Establish a Registry for Alzheimer's disease (CERAD) word learning subtest (WLT) and CERAD delayed recall test (DRT), the animal fluency test (AFT) and the digit symbol substitution test (DSST) was used. Dietary inflammatory index (DII) was computed via nutrition datasets. Mediation analysis tested the effects of DII and vitamin D levels in the association of mean probing depth (PD) and attachment loss (AL) in all four cognitive tests. Periodontitis patients obtained worse cognitive test scores than periodontally healthy individuals. DII was negatively associated with CERAD-WLT, CERAD-DRT, AFT and DSST, and was estimated to mediate between 9.2% and 36.4% of the total association between periodontitis with cognitive dysfunction (p < 0.05). Vitamin D showed a weak association between CERAD-DRT, AFT and DSST and was estimated to between 8.1% and 73.2% of the association between periodontitis and cognitive dysfunction (p < 0.05). The association between periodontitis and impaired cognitive function seems to be mediated both by a proinflammatory dietary load and vitamin D deficiency. Future studies should further explore these mediators in the periodontitis-cognitive decline link.

Vitamins in Alzheimer's Disease-Review of the Latest Reports

Alzheimer's disease (AD) is the most common form of dementia, and the aging of the population means that the number of cases is successively increasing. The cause of the disease has not been established, but it is suggested that many factors affect it, including nutritional aspects. As part of the work, the PubMed database has been searched, beginning from 2005, for terms related to key nutritional aspects. A diet rich in antioxidant vitamins can improve the cognitive functions of patients. Thanks to an adequate intake of B vitamins, homocysteine levels are reduced, which indirectly protects against the development of the disease. A properly balanced diet, as well as the use of appropriate supplementation, can contribute to improving the clinical condition of patients with AD.

Is poor self-rated sleep quality associated with elevated systemic inflammation in healthy older adults?

OBJECTIVE

Examine subjective sleep quality and inflammation among healthy older adults participating in the Australian Research Council Longevity Intervention (ARCLI).

METHODS

Data was taken from a sub-set of 232 participants aged between 60-70 years (M = 65.88 ± SD 4.08 years) who participated in the baseline assessment phase of the Australian Research Council Longevity Intervention (ARCLI) study. Subjective sleep was assessed via the Leeds Sleep Evaluation Questionnaire (LSEQ). Inflammatory markers (TNF-α, IL-1β, IL-6, IL-10, IL-2, IFN-γ, IL-4, hs-CRP) were derived from whole blood. Correlation and multiple regression analyses were used to examine associations between each of the four sleep outcome variables and inflammatory outcomes, examined as a group and following gender stratification.

RESULTS

Difficulties getting to sleep were independently associated with higher IL-2 [F_(1,156) = 4.62, adjusted R² = 0.02, p = 0.03] and IL-1β [F_(1,141) = 8.52, adjusted R² = 0.05, p = 0.004] (whole group). Difficulties getting to sleep were associated with greater IL-1β [males: F_(1,58) = 7.36, adjusted R² = 0.097 p = 0.009; females: F _(1,81) = 4.25, R² = 0.038, p = 0.04], and negatively associated with hs-CRP (women) [F _(1,129) = 4.71, R² = 0.028, p = 0.032].

DISCUSSION

Subjective sleep-onset difficulties are associated with systemic inflammation.

The Many Faces of Emerging and Reemerging Infectious Disease

The emergence of disease threats can take many forms, from the adaptation of a traditionally zoonotic pathogen for efficient spread in humans, to the development of antibiotic resistance in well-known pathogens, to the creation of new niches for established disease through social and societal changes. In this commentary, the authors explore these various facets of disease emergence through the lens of the papers included in this issue of Epidemiologic Reviews. The authors explore multiple aspects of emergence and the ways in which emergent pathogens can be controlled with the limited tools available. In doing so, they put the papers in this issue in the context of the broader research agenda around understanding and combatting emergent pathogens.