Distinctive subgingival microbial signatures in older adults with different levels of cognitive function.

AIM: To examine association between subgingival microbial signatures and levels of cognitive impairment in older adults. MATERIALS AND METHODS: We analysed subgingival plaque samples and 16S ribosomal RNA sequences for microbiota among 165 participants (normal controls [NCs]: 40, subjective cognitive decline [SCD]: 40, mild cognitive impairment [MCI]: 49 and dementia: 36). RESULTS: The bacterial richness was lower among individuals with worse cognitive function, and subgingival microbial communities differed significantly among the four groups. Declining cognitive function was associated with decreasing relative abundance of genera Capnocytophaga, Saccharibacteria_genera_incertae_sedis, Lautropia and Granulicatella, and increasing abundance of genus Porphyromonas. Moreover, there were differentially abundant genera among the groups. Random forest model based on subgingival microbiota could distinguish between cognitive impairment and NC (AUC = 0.933, 95% confidence interval 0.873-0.992). Significant correlations were observed between oral microbiota and sex, Montreal Cognitive Assessment (MoCA) score and Mini-Mental State Examination score. Partial correlation analysis showed that Leptotrichia and Burkholderia were closely negatively associated with the MoCA score after adjusting for multiple covariates. Gene function was not significantly different between SCD and NC groups, whereas three homozygous genes were altered in MCI patients and two in dementia patients. CONCLUSIONS: This is the first study to demonstrate an association between the composition, function and metabolic pathways of subgingival microbiota and different levels of cognitive function among older individuals. Future cohort studies should assess its diagnostic usefulness for cognitive impairment.

Pneumonia Readmissions in Older Adults With Dementia.

BACKGROUND/OBJECTIVES: Pneumonia readmissions have significant quality of care and policy implications for patients and health care providers. Research indicates that initiatives to decrease readmissions should target high-risk subgroups. Older adults with dementia have an increased risk of pneumonia and subsequent hospitalizations, suggesting that they may be at high-risk of pneumonia readmissions. The purpose of this study was to determine if associations between patient factors and readmission rates differ for older adults with and without dementia who were hospitalized for pneumonia. DESIGN: This was a retrospective study of secondary data. PARTICIPANTS: A nationally representative sample of 389,198 discharge records was extracted from the 2013 Nationwide Readmission Database. MEASURES: Differences between groups were analyzed using χ and t tests. A generalized linear model was utilized to examine associations between patient factors and pneumonia readmissions. RESULTS: Significant differences were found (P<0.001) when comparing patient characteristics of older adults with and without dementia who were readmitted. Older adults with dementia had a readmission rate of 23.5% and were 2.9 times more likely to be readmitted (odds ratio; 95% confidence interval, 1.93, 4.40) than older adults without dementia. Associations were calculated using a generalized linear model with dementia included as an interactive effect. Dementia significantly modified (P<0.05) the relationship between pneumonia readmissions and 4 factors; (a) discharge disposition, (b) chronic conditions, (c) risk of mortality, and (d) median household income. CONCLUSIONS: Classifying older adults with dementia as a high-risk subgroup for pneumonia readmissions is supported by the findings of this study. Development of strategies to reduce pneumonia readmissions that are tailored to individuals with dementia should be considered.

Intraventricular haemorrhage and seizures in a patient with dementia: a case of chronic neurobrucellosis.

Brucellosis is the most commonly reported zoonosis. Nervous system participation can occur at any stage of the disease either in acute or subacute or chronic form. Isolated nervous system involvement or neurobrucellosis is a relatively rare form of the disease. We describe an unusual case of an older patient with dementia with recent onset of seizures in the context of primary isolated intraventricular haemorrhage, diagnosed as chronic neurobrucellosis.

Fecal Microbiome Among Nursing Home Residents with Advanced Dementia and Clostridium difficile.

BACKGROUND/OBJECTIVES: Patients colonized with toxinogenic strains of Clostridium difficile have an increased risk of subsequent infection. Given the potential role of the gut microbiome in increasing the risk of C. difficile colonization, we assessed the diversity and composition of the gut microbiota among long-term care facility (LTCF) residents with advanced dementia colonized with C. difficile. DESIGN: Retrospective analysis of rectal samples collected during a prospective observational study. SETTING: Thirty-five nursing homes in Boston, Massachusetts. PARTICIPANTS: Eighty-seven LTCF residents with advanced dementia. MEASUREMENTS: Operational taxonomic units were identified using 16S rRNA sequencing. Samples positive for C. difficile were matched to negative controls in a 1:3 ratio and assessed for differences in alpha diversity, beta diversity, and differentially abundant features. RESULTS: Clostridium difficile sequence variants were identified among 7/87 (8.04%) residents. No patient had evidence of C. difficile infection. Demographic characteristics and antimicrobial exposure were similar between the seven cases and 21 controls. The overall biodiversity among cases and controls was reduced with a median Shannon index of 3.2 (interquartile range 2.7-3.9), with no statistically significant differences between groups. The bacterial community structure was significantly different among residents with C. difficile colonization versus those without and included a predominance of Akkermansia spp., Dermabacter spp., Romboutsia spp., Meiothermus spp., Peptoclostridium spp., and Ruminococcaceae UGC 009. CONCLUSION: LTCF residents with advanced dementia have substantial dysbiosis of their gut microbiome. Specific taxa characterized C. difficile colonization status.

Microbial origins of chronic diseases.

Chronic diseases such as cardiovascular disease and cancer are among the leading causes of death worldwide and have been on the rise over the past decade. Associations between microbial agents and development of chronic diseases have been made in the past, and new connections are currently being assessed. Investigators are examining the relationship between infectious agents and chronic disease using new technologies with more rigor and specificity. This review examines microbial agents' links to and associations with cardiovascular diseases, cancer, neurodegenerative diseases, renal diseases, psychiatric disorders, and obesity and addresses the important role of the human microbiome in maintenance of health and its potential role in chronic diseases. These associations and relationships will impact future research priorities, surveillance approaches, treatment strategies, and prevention programs for chronic diseases.

Application of Metagenomics Sequencing in a Patient with Dementia: A New Case Report.

(1) Background: The study of the microbiome is crucial for its role in major systemic diseases, in particular the oral and gut microbiota. In recent years, the study of microorganisms correlated, for example, with neurodegenerative disease has increased the prospect of a possible link between gut microbiota and the brain. Here, we report a new case concerning a patient who was initially evaluated genetically for dementia and late-onset dyskinesia, and later tested with 16S metagenomics sequencing. (2) Methods: Starting from a buccal swab, we extracted bacterial DNA and then we performed NGS metagenomics sequencing based on the amplification of the hypervariable regions of the 16S rRNA gene in bacteria. (3) Results: The sequencing revealed the presence of the Spirochaetes phylum, a pathogenic bacterium generally known to be capable of migrating to the Central Nervous System. (4) Conclusions: Oral infections, as our results suggest, could be possible contributing factors to various neurodegenerative conditions.

Relationship Between Plasma Lipopolysaccharides, Gut Microbiota, and Dementia: A Cross-Sectional Study.

BACKGROUND: Previous studies have demonstrated associations between gut microbiota, microbial metabolites, and cognitive decline. However, relationships between these factors and lipopolysaccharides (LPS; molecules of the outer membrane of gram-negative bacteria) remain controversial. OBJECTIVE: To evaluate associations between plasma LPS, gut microbiota, and cognitive function. METHODS: We performed a cross-sectional sub-analysis of data of 127 participants (women: 58%, mean age: 76 years) from our prospective cohort study regarding the relationship between gut microbiota and cognitive function. We enrolled patients who visited our memory clinic and assessed demographics, dementia-related risk factors, cognitive function, brain imaging, gut microbiomes, and microbial metabolites. We evaluated relationships between cognitive decline and plasma LPS using multivariable logistic regression analyses. RESULTS: Plasma LPS concentration increased with increasing degree of cognitive decline and total cerebral small vessel disease (SVD) score (Kruskal-Wallis test; p = 0.016 and 0.007, respectively). Participants with high plasma LPS concentrations tended to have lower concentrations of gut microbial metabolites, such as lactic acid and acetic acid, and were less likely to consume fish and shellfish (44.7% versus 69.6%, p = 0.027) than those with low plasma LPS concentrations. Multivariable analyses revealed that plasma LPS concentration was independently associated with the presence of mild cognitive impairment in participants without dementia (odds ratio: 2.09, 95% confidence interval: 1.14-3.84, p = 0.007). CONCLUSION: In this preliminary study, plasma LPS concentration was associated with both cognitive decline and cerebral SVD and significantly correlated with beneficial gut microbial metabolites. Plasma LPS may be a risk factor for cognitive decline.

Infectious causes of rapidly progressive dementia.

Infections represent an uncommon but important to recognize cause of rapidly progressive dementia, as diagnosis and treatment may produce a favorable outcome in selected instances. This article reviews infectious causes of rapidly progressive dementia, including selected viruses, bacteria, fungi, parasites, and prion diseases. Epidemiology, clinical manifestations, imaging characteristics, laboratory diagnosis, and treatment options are discussed.

Progressive dementia associated with ataxia or obesity in patients with Tropheryma whipplei encephalitis.

BACKGROUND: Tropheryma whipplei, the agent of Whipple's disease, causes localised infections in the absence of histological digestive involvement. Our objective is to describe T. whipplei encephalitis. METHODS: We first diagnosed a patient presenting dementia and obesity whose brain biopsy and cerebrospinal fluid specimens contained T. whipplei DNA and who responded dramatically to antibiotic treatment. We subsequently tested cerebrospinal fluid specimens and brain biopsies sent to our laboratory using T. whipplei PCR assays. PAS-staining and T. whipplei immunohistochemistry were also performed on brain biopsies. Analysis was conducted for 824 cerebrospinal fluid specimens and 16 brain biopsies. RESULTS: We diagnosed seven patients with T. whipplei encephalitis who demonstrated no digestive involvement. Detailed clinical histories were available for 5 of them. Regular PCR that targeted a monocopy sequence, PAS-staining and immunohistochemistry were negative; however, several highly sensitive and specific PCR assays targeting a repeated sequence were positive. Cognitive impairments and ataxia were the most common neurologic manifestations. Weight gain was paradoxically observed for 2 patients. The patients' responses to the antibiotic treatment were dramatic and included weight loss in the obese patients. CONCLUSIONS: We describe a new clinical condition in patients with dementia and obesity or ataxia linked to T. whipplei that may be cured with antibiotics.

Central nervous system tuberculosis masquerading as primary dementia: a case report.

Primary dementias are the most common cause of memory impairment in patients above the age of 60. Hypothyroidism, depression, vitamin B12 deficiency and infectious diseases such as syphilis at times may present with memory impairment mimicking primary dementias in their clinical presentation. We present here a 64-year-old female who presented with complaints of forgetfulness, confusion, memory loss and impaired concentration for the past 3 months. Neuroimaging and computed tomography of the chest were suggestive of active tuberculosis. Anti-tubercular therapy led to resolution of enhancing lesions in the brain and abatement of memory deficits.

Helicobacter pylori infection and risk for developing dementia: an evidence-based meta-analysis of case-control and cohort studies.

BACKGROUND: Infection with multiple pathogens may play a key role in the pathogenesis of dementia. Whether Helicobacter pylori (H. pylori) infection is associated causally with dementia is controversial. OBJECTIVE: We conduct a meta-analysis of case-control and cohort studies on the association between H. pylori infection and the risk for all-cause and Alzheimer's disease (AD) dementia. METHODS: Two independent reviewers searched the PubMed, Cochrane Library, and Embase databases with English language restrictions from the date of conception to September 18, 2020. The primary analysis was as follows: the exposure variable was H. pylori infection, and the outcome was incident all-cause and AD dementia. Pooled odds ratios (OR), relative risk (RR), and corresponding 95% confidence intervals (CI) were obtained using the fixed-or random-effect model. Forest plots were generated to summarize the results. RESULTS: Ten studies involving 96,561 participants were included in the meta-analysis: 5 case-control studies and 5 cohort studies. The overall pooled cohort studies showed a significant positive association between H. pylori infection and all-cause dementia with pooled RR of 1.36 (95% CI, 1.11-1.67). There was no association between H. pylori infection and risk for developing AD: RR of 1.33 (95% CI, 0.86-2.05) in cohort studies, and OR of 1.72 (95% CI, 0.97-3.04) in case-control studies. Significant heterogeneity was showed in each comparison group. CONCLUSION: This meta-analysis supports a positive association between H. pylori infection and the risk of all-cause dementia, but not AD dementia. Due to the interference of confounding factors, randomized controlled trials are needed to prove their causality.

Gut microbiota in dementia. Critical review of novel findings and their potential application.

There is a great deal of impetus for the comprehensive understanding of the complete pathological function, genetic information, and functional diversity of the gut microbiota that favors the development of dementia. It has been reported that patients with mild cognitive impairment and Alzheimer's disease present with several metabolic and immune-inflammatory alterations. The recently highlighted aspects of human health linked to cognitive decline include insulin-resistance, obesity, and chronic low-grade inflammation. Gut microbiota is known to produce neurotransmitters, such as GABA, acetylcholine, dopamine or serotonin, vitamins, intestinal toxins, and modulate nerve signaling - with emphasis on the vagus nerve. Additionally, gut dysbiosis results in impaired synthesis of signaling proteins affecting metabolic processes relevant to the development of Alzheimer's disease. Due to numerous links of gut microbiota to crucial metabolic and inflammatory pathways, attempts aimed at correcting the gut microflora composition may affect dementia pathology in a pleiotropic manner. Taking advantage of the metabolic effects of cold exposure on organisms by the introduction of whole-body cryostimulation in dementia patients could lead to alterations in gut microbiota and, therefore, decrease of an inflammatory response and insulin resistance, which remain one of the critical metabolic features of dementia. Further studies are needed in order to explore the potential application of recent findings and ways of achieving the desired goals.

Interactions Between the Aging Gut Microbiome and Common Geriatric Giants: Polypharmacy, Frailty, and Dementia.

The gut microbiome has pervasive bidirectional relationships with pharmacotherapy, chronic disease, and physical and cognitive function. We conducted a narrative review of the current literature to examine the relationships between the gut microbiome, medication use, sarcopenia and frailty, and cognitive impairment. Data from in vitro experiments, in vivo experiments in invertebrates and complex organisms, and humans indicate associations between the gut microbiome and geriatric syndromes. Better understanding of the direct and indirect roles of the microbiome may inform future prevention and management of geriatric syndromes.

Probiotics for dementia: a systematic review and meta-analysis of randomized controlled trials.

CONTEXT: Dementia is the fifth leading cause of death in the world. Animal studies indicate that in addition to the aging process, intestinal microbiota may play an important role in the neurodegeneration process through the modulation of the gut-brain axis. OBJECTIVE: A systematic review and meta-analysis was conducted to determine the effectiveness of probiotic and synbiotic supplementation on the cognitive function of individuals with dementia. DATA SOURCES: MEDLINE, BVS, SciELO, CENTRAL, Embase, and grey literature were searched from their inception to January 2019. STUDY SELECTION: We included data from randomized clinical trials (RCTs) that addressed dementias and assessed the following outcomes: cognitive function; inflammatory, oxidative stress, and metabolic markers; nutritional status; and intestinal microbiota composition. DATA EXTRACTION: Data searches, article selection, data extraction, and risk-of-bias assessments were performed according to the Cochrane guidelines. Data were pooled by inverse-variance random-effects meta-analyses. GRADE (Grading of Recommendations Assessment, Development, and Evaluations) was used to assess the quality of evidence. RESULTS: Data from 3 RCTs involving 161 individuals with Alzheimer's disease receiving Lactobacillus and Bifidobacterium strains showed no beneficial effect of probiotic supplementation on cognitive function (standardized mean difference, 0.56; 95%CI: -0.06 to 1.18), with very low certainty of evidence. However, probiotic supplementation improved plasma triglycerides, very-low-density lipoprotein cholesterol, insulin resistance, and plasma malondialdehyde. No RCTs included synbiotic supplementation or assessed microbiota composition. CONCLUSION: Current evidence regarding the use of probiotics and synbiotics for individuals with dementia is insufficient to support their clinical application. SYSTEMATIC REVIEW REGISTRATION: PROSPERO registration no: CRD42018116148.

Recurring Gastrointestinal Infections Increase the Risk of Dementia.

BACKGROUND: Gastrointestinal infections cause significant health problems, including those affecting the immune, musculoskeletal, and nervous system, and are one of the leading causes for death worldwide. Recent findings suggest that microbiota of the gastrointestinal tract contribute to dementia. OBJECTIVE: In this nested case-control study we investigated the role of common gastrointestinal infections on the subsequent risk of dementia. METHODS: We used a longitudinal sample of 202,806 individuals from health claims data of the largest German health insurer and applied a nested case-control design with 23,354 initial dementia cases between 2006 and 2014 and 23,354 matched controls. We used conditional logistic regression to compute odds ratios (ORs) for dementia and corresponding 95%confidence intervals (CIs), adjusting for potential confounders. RESULTS: The risk of dementia was increased in patients with recurring incidences of quarters with diagnosed gastrointestinal infections when compared to the unexposed population (one quarter: OR = 1.49, 95%CI = 1.40-1.58; two quarters: OR = 1.70, 95%CI = 1.51-1.91; three or more quarters: OR = 1.64, 95%CI = 1.40-1.93), adjusted for potential confounders. CONCLUSION: Our findings suggest that recurring gastrointestinal infections are associated with an increased risk of subsequent dementia.

Identification of Faecalibacterium prausnitzii strains for gut microbiome-based intervention in Alzheimer's-type dementia.

Evidence linking the gut-brain axis to Alzheimer's disease (AD) is accumulating, but the characteristics of causally important microbes are poorly understood. We perform a fecal microbiome analysis in healthy subjects and those with mild cognitive impairment (MCI) and AD. We find that Faecalibacterium prausnitzii (F. prausnitzii) correlates with cognitive scores and decreases in the MCI group compared with the healthy group. Two isolated strains from the healthy group, live Fp360 and pasteurized Fp14, improve cognitive impairment in an AD mouse model. Whole-genome comparison of isolated strains reveals specific orthologs that are found only in the effective strains and are more abundant in the healthy group compared with the MCI group. Metabolome and RNA sequencing analyses of mouse brains provides mechanistic insights into the relationship between the efficacy of pasteurized Fp14, oxidative stress, and mitochondrial function. We conclude that F. prausnitzii strains with these specific orthologs are candidates for gut microbiome-based intervention in Alzheimer's-type dementia.

[Association between the Gut Microbiome and Cognitive Function].

Dysregulation of the gut microbiome is associated with several life-threatening conditions, and might therefore represent a useful target for the prevention of dementia. However, the relationship between the gut microbiome and dementia has not yet been fully elucidated. Here, we recruited outpatients visiting our memory clinic to participate in this study. Information for patient demographics, various risk factors, and daily activities was collected, and cognitive function was assessed using neuropsychological tests and magnetic resonance imaging scans. Fecal samples were obtained, and the gut microbiome was assessed by terminal restriction fragment length polymorphism (T-RFLP) analysis, one of the most well-established and reliable 16S ribosomal RNA-based methods for classifying gut microbiota. Multivariable logistic regression models were used to identify factors independently associated with dementia and mild cognitive impairment. Graphical modelling was used to illustrate mutual associations. We analyzed 128 eligible patients (female: 59%, mean age: 74.2±8.7 years, mean Mini Mental State Examination score 24). Multivariable analyses showed that enterotype I and enterotype III bacteria were strongly associated with dementia, independent of traditional dementia biomarkers. Further studies investigating metabolites of gut microbes are needed to determine the mechanism underlying this association.

Association of Seropositivity to Borrelia burgdorferi With the Risk of Neuropsychiatric Disorders and Functional Decline in Older Adults: The Aging Multidisciplinary Investigation Study.

Importance: Exposure to Borrelia burgdorferi (Bb) has been reported to be associated with certain neuropsychiatric disorders. Objective: To establish the association between seropositivity to Bb and incidental neuropsychiatric disorders (eg, cognitive decline, incident dementia, and depressive symptoms) as well as functional decline. Design, Setting, and Participants: This prospective, 6-year follow-up cohort study was conducted in a rural southwestern region of France and included 689 retired farmers 65 years or older randomly recruited from the Farmer Health Insurance System who agreed to submit a blood sample and were participants in the Aging Multidisciplinary Investigation study, an ongoing epidemiological prospective study of aging initiated in 2007. The data were analyzed from April to May 2019. Exposures: Borrelia burgdorferi serology testing was performed in a 2-tiered approach. During the follow-up period, cognitive decline, incident dementia, depressive symptoms, and functional decline were repeatedly assessed. Main Outcomes and Measures: Diagnosis of dementia relied on a 3-step procedure; cognitive decline was determined using the Mini-Mental State Examination and depressive symptomatology was assessed using the Center for Epidemiologic Studies Depression scale. For disability, scores on instrumental and basic activities of daily living were investigated. Results: Of 689 participants, 432 (62.2%) were men and the mean (SD) age was 75.8 (6.4) years. The seroprevalence rate of Bb was 6.5%. At baseline, compared with Bb- participants, those who were Bb+ were older, predominantly men, and had lower depressive symptoms. No association between seropositivity and any of the studied outcomes (ie, cognitive decline, depressive symptoms, or functional decline) was found in the crude analysis and after adjusting for confounding variables. Regarding incident dementia, no increased risk was found among Bb+ participants (hazard ratio, 0.42; 95% CI, 0.1-1.17; adjusted for diverse confounders). Conclusions and Relevance: To our knowledge, this is one of the few longitudinal studies exploring the risk of neuropsychiatric disorders and functional decline associated with exposure to Bb. Despite its limitations (eg, a lack of information if clinical manifestations of Lyme borreliosis existed, date of exposure, or treatment received), this study suggests that seropositivity to Bb is not a risk factor for incidental neuropsychiatric disorders and functional decline.

Clinical and Bacterial Markers of Periodontitis and Their Association with Incident All-Cause and Alzheimer's Disease Dementia in a Large National Survey.

Microbial agents including periodontal pathogens have recently appeared as important actors in Alzheimer's disease (AD) pathology. We examined associations of clinical periodontal and bacterial parameters with incident all-cause and AD dementia as well as AD mortality among US middle-aged and older adults. Clinical [Attachment Loss (AL); probing pocket depth (PPD)] and bacterial [pathogen immunoglobulin G (IgG)] periodontal markers were investigated in relation to AD and all-cause dementia incidence and to AD mortality, using data from the third National Health and Nutrition Examination Surveys (NHANES III, 1988-1994) linked longitudinally with National Death Index and Medicare data through January 1, 2014, with up to 26 years of follow-up. Sex- and age-specific multivariable-adjusted Cox proportional hazards models were conducted. Among those ≥65 years, AD incidence and mortality were consistently associated with PPD, two factors and one cluster comprised of IgG titers against Porphyromonas gingivalis (P. gingivalis), Prevotella melaninogenica (P. melaninogenica) and Campylobacter rectus (C. rectus) among others. Specifically, AD incidence was linked to a composite of C. rectus and P. gingivalis titers (per SD, aHR = 1.22; 95% CI, 1.04-1.43, p = 0.012), while AD mortality risk was increased with another composite (per SD, aHR = 1.46; 95% CI, 1.09-1.96, p = 0.017) loading highly on IgG for P. gingivalis, Prevotella intermedia, Prevotella nigrescens, Fusobacterium nucleatum, C. rectus, Streptococcus intermedius, Capnocylophaga Ochracea, and P. melaninogenica. This study provides evidence for an association between periodontal pathogens and AD, which was stronger for older adults. Effectiveness of periodontal pathogen treatment on reducing sequelae of neurodegeneration should be tested in randomized controlled trials.