-
PloS One 2023Alzheimer's disease (AD) is a neurodegenerative disorder that causes gradual memory loss. AD and its prodromal stage of mild cognitive impairment (MCI) are marked by... (Meta-Analysis)
Meta-Analysis
BACKGROUND
Alzheimer's disease (AD) is a neurodegenerative disorder that causes gradual memory loss. AD and its prodromal stage of mild cognitive impairment (MCI) are marked by significant gut microbiome perturbations, also known as gut dysbiosis. However, the direction and extent of gut dysbiosis have not been elucidated. Therefore, we performed a meta-analysis and systematic review of 16S gut microbiome studies to gain insights into gut dysbiosis in AD and MCI.
METHODS
We searched MEDLINE, Scopus, EMBASE, EBSCO, and Cochrane for AD gut microbiome studies published between Jan 1, 2010 and Mar 31, 2022. This study has two outcomes: primary and secondary. The primary outcomes explored the changes in α-diversity and relative abundance of microbial taxa, which were analyzed using a variance-weighted random-effects model. The secondary outcomes focused on qualitatively summarized β-diversity ordination and linear discriminant analysis effect sizes. The risk of bias was assessed using a methodology appropriate for the included case-control studies. The geographic cohorts' heterogeneity was examined using subgroup meta-analyses if sufficient studies reported the outcome. The study protocol has been registered with PROSPERO (CRD42022328141).
FINDINGS
Seventeen studies with 679 AD and MCI patients and 632 controls were identified and analyzed. The cohort is 61.9% female with a mean age of 71.3±6.9 years. The meta-analysis shows an overall decrease in species richness in the AD gut microbiome. However, the phylum Bacteroides is consistently higher in US cohorts (standardised mean difference [SMD] 0.75, 95% confidence interval [CI] 0.37 to 1.13, p < 0.01) and lower in Chinese cohorts (SMD -0.79, 95% CI -1.32 to -0.25, p < 0.01). Moreover, the Phascolarctobacterium genus is shown to increase significantly, but only during the MCI stage.
DISCUSSION
Notwithstanding possible confounding from polypharmacy, our findings show the relevance of diet and lifestyle in AD pathophysiology. Our study presents evidence for region-specific changes in abundance of Bacteroides, a major constituent of the microbiome. Moreover, the increase in Phascolarctobacterium and the decrease in Bacteroides in MCI subjects shows that gut microbiome dysbiosis is initiated in the prodromal stage. Therefore, studies of the gut microbiome can facilitate early diagnosis and intervention in Alzheimer's disease and perhaps other neurodegenerative disorders.
Topics: Humans; Female; Middle Aged; Aged; Male; Alzheimer Disease; Gastrointestinal Microbiome; Dysbiosis; Prodromal Symptoms; Bacteroides; Cognitive Dysfunction
PubMed: 37224131
DOI: 10.1371/journal.pone.0285346 -
Frontiers in Neuroscience 2023Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by declining cognitive ability. Currently, there are no effective treatments for this...
BACKGROUND AND OBJECTIVE
Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by declining cognitive ability. Currently, there are no effective treatments for this condition. However, certain measures, such as nutritional interventions, can slow disease progression. Therefore, the objective of this systematic review was to identify and map the updates of the last 5 years regarding the nutritional status and nutritional interventions associated with AD patients.
STUDY DESIGN
A systematic review.
METHODS
A search was conducted for randomized clinical trials, systematic reviews, and meta-analyses investigating the association between nutritional interventions and AD published between 2018 and 2022 in the PubMed, Web of Science, Scopus, and Cochrane Library databases. A total of 38 studies were identified, of which 17 were randomized clinical trials, and 21 were systematic reviews and/or meta-analyses.
RESULTS
The results show that the western diet pattern is a risk factor for developing AD. In contrast, the Mediterranean diet, ketogenic diet, and supplementation with omega-3 fatty acids and probiotics are protective factors. This effect is significant only in cases of mild-to-moderate AD.
CONCLUSION
Certain nutritional interventions may slow the progression of AD and improve cognitive function and quality of life. Further research is required to draw more definitive conclusions.
PubMed: 37214392
DOI: 10.3389/fnins.2023.1147177 -
Journal of Clinical Medicine Feb 2020The evidence of a connection between the peripheral inflammatory processes and neurodegenerative diseases of the central nervous system is becoming more apparent. This... (Review)
Review
The evidence of a connection between the peripheral inflammatory processes and neurodegenerative diseases of the central nervous system is becoming more apparent. This review of the related literature highlights the most recent clinical, epidemiological, and in vitro studies trying to investigate possible connections between periodontal bacteria and the onset and progression of Alzheimer's disease. This review was conducted by searching databases such as PubMed and Scopus using keywords or combinations such as Alzheimer's Disease AND periodontal or dementia AND periodontitis OR periodontal. After eliminating overlaps and screening the articles not related to these issues, we identified 1088 records and proceeded to the selection of articles for an evaluation of the associative assumptions. The hypothesis suggested by the authors and confirmed by the literature is that the bacterial load and the inflammatory process linked to periodontal disease can intensify inflammation at the level of the central nervous system, favoring the occurrence of the disease. The analysis of the literature highlights how periodontal disease can directly contribute to the peripheral inflammatory environment by the introduction of periodontal or indirect pathogenic bacteria and proinflammatory cytokines locally produced at the periodontal level following bacterial colonization of periodontal defects.
PubMed: 32054121
DOI: 10.3390/jcm9020495 -
Neurological Sciences : Official... Jul 2022To explore the pathogenetic hypothesis provided to explain the comorbidity of anxious and depressive symptomatology and AD and to assess the association between anxious... (Review)
Review
OBJECTIVES
To explore the pathogenetic hypothesis provided to explain the comorbidity of anxious and depressive symptomatology and AD and to assess the association between anxious and depressive symptoms and the AD-related cognitive impairment.
METHODS
In October 2020 and March 2021, PsycINFO, Embase, Ovid, and CINAHL were searched for peer-reviewed original articles investigating anxiety and/or depression in AD.
RESULTS
A total of 14,760 studies were identified and 34 papers on AD patients were included in the review. Suggested biological causes of depression and anxiety in AD include higher strychnine-sensitive glycine receptor (GlyRS) functioning and selective reduction of N-methyl-D-aspartate (NMDA) receptor NR2A density, cortical and limbic atrophy, lower resting cortical metabolism, lower CSF Aβ42 and higher t-tau and p-tau levels, and neuritic plaques. At the same time, dysthymia arises in the early stages of AD as an emotional reaction to the progressive cognitive decline and can cause it; anxiety can appear as an initial compensating behaviour; and depression might be related to AD awareness and loss of functional abilities. Affective symptoms and the expression of the depressive symptoms tend to reduce as AD progresses.
CONCLUSION
The neurodegeneration of areas and circuits dealing with emotions can elicit anxiety and depression in AD. In the early stages of the disease, anxiety and depression could arise as a psychological reaction to AD and due to coping difficulties. In late AD stages, the cognitive impairment reduces the emotional responses and their expression. Anxiety and depression are more intense in early-onset AD, due to the major impact of AD on the individual.
Topics: Alzheimer Disease; Anxiety; Anxiety Disorders; Biomarkers; Cognitive Dysfunction; Depression; Humans; Receptors, N-Methyl-D-Aspartate
PubMed: 35461471
DOI: 10.1007/s10072-022-06068-x -
International Journal of Environmental... Nov 2022Declines in activities of daily living (ADL) and instrumental activities of daily living (IADL) performances due to cognitive impairments hinder mild cognitive... (Meta-Analysis)
Meta-Analysis Review
Declines in activities of daily living (ADL) and instrumental activities of daily living (IADL) performances due to cognitive impairments hinder mild cognitive impairment (MCI) and Alzheimer's disease (AD) patients' independent and safe daily lives. In order to prevent and treat this, several cognitive interventions have been implemented, but their ecological validity was not ensured due to that their contents are far from real life. Virtual reality (VR) can resemble real life with immersive stimuli, but there have been few studies confirming its ecological effects on ADL and IADL. Therefore, this study conducted a meta-analysis of VR-based cognitive training to investigate its ecological effects on ADL and IADL in MCI and AD patients. From February 2012 to February 2022, a search was conducted for articles published in PubMed, Cochrane, Science Direct, and Web of Science. Quality assessment was assessed by the PEDro scale, and the Cochrane Collaboration tool was used to assess risk of bias. Publication bias was assessed by Egger's regression. Five studies that met inclusion criteria were included in this study. The VR-based cognitive training showed significant effects on ADL and IADL in both MCI and AD patients. When comparing effects in each group, both MCI and AD patients showed significant effects on ADL and IADL, but MCI patients showed lower effects on ADL and IADL than AD patients. The results indicated that VR-based cognitive training would be beneficial to improve ADL and IADL in MCI and AD patients, suggesting that VR-based cognitive training is ecologically valid.
Topics: Humans; Activities of Daily Living; Alzheimer Disease; Cognitive Training; Cognitive Dysfunction; Virtual Reality; Neuropsychological Tests
PubMed: 36497946
DOI: 10.3390/ijerph192315875 -
Journal of Neurochemistry Mar 2021Similar to dementia, the risk for developing type 2 diabetes mellitus (T2DM) increases with age, and T2DM also increases the risk for dementia, particularly Alzheimer's...
Similar to dementia, the risk for developing type 2 diabetes mellitus (T2DM) increases with age, and T2DM also increases the risk for dementia, particularly Alzheimer's disease (AD). Although T2DM is primarily a peripheral disorder and AD is a central nervous system disease, both share some common features as they are chronic and complex diseases, and both show involvement of oxidative stress and inflammation in their progression. These characteristics suggest that T2DM may be associated with AD, which gave rise to a new term, type 3 diabetes (T3DM). In this study, we searched for matching peripheral proteomic biomarkers of AD and T2DM based in a systematic review of the available literature. We identified 17 common biomarkers that were differentially expressed in both patients with AD or T2DM when compared with healthy controls. These biomarkers could provide a useful workflow for screening T2DM patients at risk to develop AD.
Topics: Alzheimer Disease; Animals; Biomarkers; Diabetes Mellitus, Type 2; Humans; Proteomics
PubMed: 32909269
DOI: 10.1111/jnc.15166 -
Annals of Family Medicine 2024We conducted a meta-analysis to evaluate clinically meaningful benefits and harms of monoclonal antibodies targeting amyloid in patients with Alzheimer dementia. (Meta-Analysis)
Meta-Analysis Review
PURPOSE
We conducted a meta-analysis to evaluate clinically meaningful benefits and harms of monoclonal antibodies targeting amyloid in patients with Alzheimer dementia.
METHODS
We searched PubMed, Cochrane CENTRAL, and 5 trial registries, as well as the reference lists of identified studies. We included randomized controlled trials comparing a monoclonal antibody with placebo at a dose consistent with that used in phase 3 trials or for Food and Drug Administration approval. Studies had to report at least 1 clinically relevant benefit or harm. Data were extracted independently by at least 2 researchers for random effects meta-analysis. Changes in cognitive and functional scales were compared between groups, and each difference was assessed to determine if it met the minimal clinically important difference (MCID).
RESULTS
We identified 19 publications with 23,202 total participants that evaluated 8 anti-amyloid antibodies. There were small improvements over placebo in the Alzheimer's Disease Assessment Scale (ADAS)-Cog-11 to -14 score (standardized mean difference = -0.07; 95% CI, -0.10 to -0.04), Mini Mental State Examination score (0.32 points; 95% CI, 0.13 to 0.50), and Clinical Dementia Rating-Sum of Boxes scale score (mean difference =-0.18 points; 95% CI, -0.34 to -0.03), and the combined functional scores (standardized mean difference = 0.09; 95% CI, 0.05 to 0.13). None of the changes, including those for lecanemab, aducanumab, and donanemab, exceeded the MCID. Harms included significantly increased risks of amyloid-related imaging abnormalities (ARIA)-edema (relative risk [RR] = 10.29; number needed to harm [NNH] = 9), ARIA-hemorrhage (RR = 1.74; NNH = 13), and symptomatic ARIA-edema (RR = 24.3; NNH = 86).
CONCLUSIONS
Although monoclonal antibodies targeting amyloid provide small benefits on cognitive and functional scales in patients with Alzheimer dementia, these improvements are far below the MCID for each outcome and are accompanied by clinically meaningful harms.
Topics: United States; Humans; Alzheimer Disease; Antibodies, Monoclonal; Mental Status and Dementia Tests; Edema; Antibodies, Monoclonal, Humanized
PubMed: 38253509
DOI: 10.1370/afm.3050 -
Ageing Research Reviews Dec 2022Dementia prevention research has progressed rapidly in recent years, with publication of several large lifestyle intervention trials, and renewed interest in... (Review)
Review
Dementia prevention research has progressed rapidly in recent years, with publication of several large lifestyle intervention trials, and renewed interest in pharmacological interventions, notably for individuals with Alzheimer's disease biomarkers, warranting an updated review of results and methodology. We identified 112 completed trials testing the efficacy of single-domain pharmacological (n = 33, 29%), nutritional (n = 27, 24%), physical activity (n = 18, 16%) and cognitive stimulation (n = 13, 12%), or multidomain (n = 22, 20%) interventions on incident dementia, or a relevant intermediate marker (e.g. cognitive function, biomarkers or dementia risk scores) in people without dementia. The earliest trials tested pharmacological interventions or nutritional supplements, but lifestyle interventions predominated in the last decade. In total, 21 (19%) trials demonstrated a clear beneficial effect on the pre-specified primary outcome (or all co-primary outcomes), but only two (10%) were large-scale (testing blood pressure lowering (Syst-Eur) or multidomain (FINGER) interventions on incident dementia and cognitive change in cognitive function, respectively). Of the 116 ongoing trials, 40% (n = 46) are testing multidomain interventions. Recent methodological shifts concern target populations, primary outcome measures, and intervention design, but study design remains constant (parallel group randomised controlled trial). Future trials may consider using adaptive trials or interventions, and more targeted approaches, since certain interventions may be more effective in certain subgroups of the population, and at specific times in the life-course. Efforts should also be made to increase the representativeness and diversity of prevention trial populations.
Topics: Humans; Cognitive Dysfunction; Cognition; Alzheimer Disease; Cognitive Behavioral Therapy; Life Style; Randomized Controlled Trials as Topic
PubMed: 36336171
DOI: 10.1016/j.arr.2022.101777 -
Translational Psychiatry Apr 2022Polysomnography (PSG) studies of sleep changes in Alzheimer's disease (AD) have reported but not fully established the relationship between sleep disturbances and AD. To... (Meta-Analysis)
Meta-Analysis
Polysomnography (PSG) studies of sleep changes in Alzheimer's disease (AD) have reported but not fully established the relationship between sleep disturbances and AD. To better detail this relationship, we conducted a systematic review and meta-analysis of reported PSG differences between AD patients and healthy controls. An electronic literature search was conducted in EMBASE, MEDLINE, All EBM databases, CINAHL, and PsycINFO inception to Mar 2021. Twenty-eight studies were identified for systematic review, 24 of which were used for meta-analysis. Meta-analyses revealed significant reductions in total sleep time, sleep efficiency, and percentage of slow-wave sleep (SWS) and rapid eye movement (REM) sleep, and increases in sleep latency, wake time after sleep onset, number of awakenings, and REM latency in AD compared to controls. Importantly, both decreased SWS and REM were significantly associated with the severity of cognitive impairment in AD patients. Alterations in electroencephalogram (EEG) frequency components and sleep spindles were also observed in AD, although the supporting evidence for these changes was limited. Sleep in AD is compromised with increased measures of wake and decreased TST, SWS, and REM sleep relative to controls. AD-related reductions in SWS and REM sleep correlate with the degree of cognitive impairment. Alterations in sleep EEG frequency components such as sleep spindles may be possible biomarkers with relevance for diagnosing AD although their sensitivity and specificity remain to be clearly delineated. AD-related sleep changes are potential targets for early therapeutic intervention aimed at improving sleep and slowing cognitive decline.
Topics: Alzheimer Disease; Humans; Polysomnography; Sleep; Sleep Wake Disorders; Sleep, REM
PubMed: 35365609
DOI: 10.1038/s41398-022-01897-y -
BMJ Open Apr 2022To examine the comparative efficacy and safety of cognitive enhancers by patient characteristics for managing Alzheimer's dementia (AD). (Meta-Analysis)
Meta-Analysis
OBJECTIVE
To examine the comparative efficacy and safety of cognitive enhancers by patient characteristics for managing Alzheimer's dementia (AD).
DESIGN
Systematic review and individual patient data (IPD) network meta-analysis (NMA) based on our previously published systematic review and aggregate data NMA.
DATA SOURCES
MEDLINE, Embase, Cochrane Methodology Register, CINAHL, AgeLine and Cochrane Central Register of Controlled Trials up to March 2016.
PARTICIPANTS
80 randomised controlled trials (RCTs) including 21 138 adults with AD, and 12 RCTs with IPD including 6906 patients.
INTERVENTIONS
Cognitive enhancers (donepezil, rivastigmine, galantamine and memantine) alone or in any combination against other cognitive enhancers or placebo.
DATA EXTRACTION AND SYNTHESIS
We requested IPD from authors, sponsors and data sharing platforms. When IPD were not available, we used aggregate data. We appraised study quality with the Cochrane risk-of-bias. We conducted a two-stage random-effects IPD-NMA, and assessed their findings using CINeMA (Confidence in Network Meta-Analysis).
PRIMARY AND SECONDARY OUTCOMES
We included trials assessing cognition with the Mini-Mental State Examination (MMSE), and adverse events.
RESULTS
Our IPD-NMA compared nine treatments (including placebo). Donepezil (mean difference (MD)=1.41, 95% CI: 0.51 to 2.32) and donepezil +memantine (MD=2.57, 95% CI: 0.07 to 5.07) improved MMSE score (56 RCTs, 11 619 participants; CINeMA score: moderate) compared with placebo. According to P-score, oral rivastigmine (OR=1.26, 95% CI: 0.82 to 1.94, P-score=16%) and donepezil (OR=1.08, 95% CI: 0.87 to 1.35, P-score=30%) had the least favourable safety profile, but none of the estimated treatment effects were sufficiently precise when compared with placebo (45 RCTs, 15 649 patients; CINeMA score: moderate to high). For moderate-to-severe impairment, donepezil, memantine and their combination performed best, but for mild-to-moderate impairment donepezil and transdermal rivastigmine ranked best. Adjusting for MMSE baseline differences, oral rivastigmine and galantamine improved MMSE score, whereas when adjusting for comorbidities only oral rivastigmine was effective.
CONCLUSIONS
The choice among the different cognitive enhancers may depend on patient's characteristics. The MDs of all cognitive enhancer regimens except for single-agent oral rivastigmine, galantamine and memantine, against placebo were clinically important for cognition (MD larger than 1.40 MMSE points), but results were quite imprecise. However, two-thirds of the published RCTs were associated with high risk of bias for incomplete outcome data, and IPD were only available for 15% of the included RCTs.
PROSPERO REGISTRATION NUMBER
CRD42015023507.
Topics: Adult; Alzheimer Disease; Donepezil; Galantamine; Humans; Memantine; Network Meta-Analysis; Nootropic Agents; Rivastigmine
PubMed: 35473731
DOI: 10.1136/bmjopen-2021-053012