Spelling suggestions: "subject:"metaanalysis"" "subject:"metanalysis""
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Does vitamin D supplementation alter plasma adipokines concentrations? A systematic review and meta-analysis of randomized controlled trials.Dinca, Madalina, Serban, Maria-Corina, Sahebkar, Amirhossein, Mikhailidis, Dimitri P, Toth, Peter P, Martin, Seth S, Blaha, Michael J, Blüher, Matthias, Gurban, Camelia, Penson, Peter, Michos, Erin D, Hernandez, Adrian V., Jones, Steven R, Banach, Maciej 30 March 2016 (has links)
We aimed to elucidate the role of vitamin D supplementation on adipokines through a systematic review and a meta-analysis of randomized placebo-controlled trials (RCTs). The search included PUBMED, Scopus, Web of Science and Google Scholar through July 1st, 2015. Finally we identified 9 RCTs and 484 participants. Meta-analysis of data from 7 studies did not find a significant change in plasma adiponectin concentrations following vitamin D supplementation (mean difference [MD]: 4.45%, 95%CI: -3.04, 11.93, p=0.244; Q=2.18, I(2)=0%). In meta-regression, changes in plasma adiponectin concentrations following vitamin D supplementation were found to be independent of treatment duration (slope: 0.25; 95%CI: -0.69, 1.19; p=0.603) and changes in serum 25-hydroxy vitamin D [25(OH)D] levels (slope: -0.02; 95%CI: -0.15, 0.12; p=0.780). Meta-analysis of data from 6 studies did not find a significant change in plasma leptin concentrations following vitamin D supplementation (MD: -4.51%, 95%CI: -25.13, 16.11, p=0.668; Q=6.41, I(2)=21.97%). Sensitivity analysis showed that this effect size is sensitive to one of the studies; removing it resulted in a significant reduction in plasma leptin levels (MD: -12.81%, 95%CI: -24.33, -1.30, p=0.029). In meta-regression, changes in plasma leptin concentrations following vitamin D supplementation were found to be independent of treatment duration (slope: -1.93; 95%CI: -4.08, 0.23; p=0.080). However, changes in serum 25(OH)D were found to be significantly associated with changes in plasma leptin levels following vitamin D supplementation (slope: 1.05; 95%CI: 0.08, 2.02; p=0.033). In conclusion, current data did not indicate a significant effect of vitamin D supplementation on adiponectin and leptin levels. / Revisión por pares
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Effect of Diastolic Dysfunction on Postoperative Outcomes after Cardiovascular Surgery: a Systematic Review and Meta-AnalysisKaw, Roop, Hernandez, Adrian V., Pasupuleti, Vinay, Deshpande, Abhishek, Nagarajan, Vijaiganesh, Bueno, Hector, Coleman, Craig I., Ioannidis, John P.A., Bhatt, Deepak L., Blackstone, Eugene H. 06 1900 (has links)
El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / Objective The objective of this study was to investigate the effect of preoperative diastolic dysfunction on postoperative mortality and morbidity after cardiovascular surgery. Methods We systematically searched for articles that assessed the prognostic role of diastolic dysfunction on cardiovascular surgery in PubMed, Cochrane Library, Web of Science, Embase and Scopus until February 2016. Twelve studies (n=8224) met our inclusion criteria. Due to scarcity of outcome events, fixed-effects meta-analysis was performed using the Mantel-Haenszel method. Results Preoperative diagnosis of diastolic dysfunction was associated with higher postoperative mortality (OR 2.41, 95% CI 1.54-3.71; p<0.0001), major adverse cardiac events (MACE) (OR 2.07, 95% CI 1.55-2.78; p <=0.0001) and prolonged mechanical ventilation (OR 2.08, 95% CI 1.04-4.16; p=0.04) in comparison to patients without diastolic dysfunction among patients who underwent cardiovascular surgery. The odds of postoperative myocardial infarction (OR: 1.29, 95% CI 0.82, 2.05; p=0.28) and atrial fibrillation (OR: 2.67; 95% CI 0.49-14.43; p=0.25) did not significantly differ between the two groups. Severity of preoperative diastolic dysfunction was associated with increased postoperative mortality (OR 21.22, 95% CI 3.74 -120.33; p=0.0006) for Grade 3 diastolic dysfunction compared with patients with normal diastolic function. Inclusion of left ventricular ejection fraction (LVEF) <40% accompanying diastolic dysfunction, did not further impact postoperative mortality (p=0.27; I2 =18%) when compared with patients with normal LVEF and diastolic dysfunction. Conclusions Presence of preoperative diastolic dysfunction was associated with higher postoperative mortality and MACE, regardless of LVEF. Mortality was significantly higher in grade III diastolic dysfunction. Keywords Diastolic dysfunction; cardiovascular surgical procedures; mortality; meta-analysis / Revisión por pares
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The role of metacognition in suicidal thinking and ruminationHallard, Robert January 2017 (has links)
The Self-Regulatory Executive Function (S-REF) model (Wells & Matthew, 2015) states that psychological disorder results from an unhelpful thinking style called the Cognitive Attentional Syndrome (CAS). The CAS incorporates worry/rumination, threat monitoring and unhelpful thought control strategies and is controlled by erroneous metacognitive beliefs. The contribution of the S-REF model to the understating of rumination (paper one) and suicidal ideation (paper two) is evaluated within this thesis. Rumination is one component of the CAS. According to the S-REF model, its execution is guided by metacognitive beliefs. Paper one describes a systematic review and meta-analysis that was undertaken to establish the nature and strength of the relationships between rumination and metacognitive beliefs. Robust relationships, of moderate strength, were observed between rumination and beliefs about its benefits and between rumination and beliefs about its negative consequences. Future research should aim to delineate causality in the observed relationships and consider confounder variables. In paper two it is argued that the S-REF conceptualisation represents a promising new approach to the understanding of suicidal ideation. The importance of considering CAS processes was supported by the study findings. Worry and punishment-related thought control strategies, alongside rumination, predicted suicidal ideation. Distraction, social control and reappraisal strategies negatively predicted suicidal ideation. Some evidence that CAS processes were controlled by erroneous metacognitive beliefs was also obtained. However, this was not conclusive and should be considered again in a larger sample. Paper three describes the development of papers one and two in more detail, highlighting and justifying the important decisions made. Further reflections on methodology are also provided to demonstrate the learning achieved.
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A comparison of tests of heterogeneity in meta-analysis.January 2001 (has links)
Lee Shun-yi. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 57-61). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Tests of Hypotheses --- p.4 / Chapter 1.2.1 --- Likelihood Ratio Statistic --- p.4 / Chapter 1.2.2 --- The Rao´ة s Score Statistic --- p.5 / Chapter 1.2.3 --- Wald's Statistic --- p.6 / Chapter 1.3 --- Notation --- p.6 / Chapter 2 --- Fixed Effects Model --- p.8 / Chapter 2.1 --- Introduction --- p.8 / Chapter 2.2 --- Pearson Chi-square Statistic --- p.9 / Chapter 2.3 --- Logistic Regression Model --- p.11 / Chapter 2.3.1 --- Testing Linear Hypotheses about the Regression Coefficients --- p.12 / Chapter 2.4 --- Combining Proportions --- p.16 / Chapter 2.4.1 --- Classical Estimators --- p.17 / Chapter 2.4.2 --- Jackknife Estimator --- p.18 / Chapter 2.4.3 --- Cross-validatory estimators --- p.19 / Chapter 3 --- Random Effects Model --- p.21 / Chapter 3.1 --- Introduction --- p.21 / Chapter 3.2 --- DerSimonian and Laird Method --- p.22 / Chapter 3.3 --- Generalized linear model with random effect --- p.24 / Chapter 3.3.1 --- Quasi-Likelihood --- p.25 / Chapter 3.3.2 --- Testing Linear Hypotheses about the Regression Coefficients --- p.26 / Chapter 3.3.3 --- MINQUE --- p.27 / Chapter 3.3.4 --- Score Test --- p.31 / Chapter 4 --- Overdispersion and Intraclass Correlation --- p.36 / Chapter 4.1 --- Introduction --- p.36 / Chapter 4.2 --- C(α) Test --- p.39 / Chapter 4.2.1 --- Correlated Binomial model and Beta-Binomial model --- p.40 / Chapter 4.2.2 --- C(α) Statistic Based On Quasi-likclihood --- p.46 / Chapter 4.3 --- Donner Statistic --- p.48 / Chapter 4.4 --- Rao and Scott Statistic --- p.51 / Chapter 5 --- Example and Discussion --- p.53 / Bibliography --- p.57
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Informational efficiency of the real estate market: A meta-analysisHerath, Shanaka, Maier, Gunther 16 April 2015 (has links) (PDF)
The growing empirical literature testing informational efficiency of real estate markets uses data from various contexts and at different levels of aggregation. The results of these studies are mixed. We use a distinctive meta-analysis to examine whether some of these study characteristics and contexts lead to a significantly higher chance for identification of an efficient real estate market. The results generated through meta-regression suggest that use of stock market data and individual level data, rather than aggregate data, significantly improves the probability of a study concluding efficiency. Additionally, the findings neither provide support for the suspicion that the view of market efficiency has significantly changed over the years nor do they indicate a publication bias resulting from such a view. The statistical insignificance of other study characteristics suggests that the outcome concerning efficiency is a context-specific random manifestation for the most part. (authors' abstract)
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Métodos bayesianos em metanálise: especificação da distribuição a priori para a variabilidade entre os estudos / Bayesian methods in meta-analysis: specication of prior distributions for the between-studies variabilitySuleimy Cristina Mazin 27 November 2009 (has links)
MAZIN, S. C.Metodos Bayesianos em Metanalise: Especicac~ao da Distribuic~ao a Priori para a Variabilidade entre os Estudos. 2009. 175f. Dissertac~ao (mestrado) - Faculdade de Medicina de Ribeir~ao Preto, Universidade de S~ao Paulo, Ribeir~ao Preto, 2009. Prossionais da saude, pesquisadores e outros responsaveis por polticas de saude s~ao frequentemente inundados com quantidades de informac~oes nem sempre manejaveis, o que torna a revis~ao sistematica uma maneira eciente de integrar o conhecimento existente gerando dados que auxiliem a tomada de decis~ao. Em uma revis~ao sistematica os dados dos diferentes estudos podem ser quantitativamente combinados por metodos estatsticos chamados metanalise. A metanalise e uma ferramenta estatstica utilizada para combinar ou integrar os resultados dos diversos estudos independentes, sobre o mesmo tema. Entre os estudos que comp~oem a metanalise pode existir uma variabilidade que n~ao e devida ao acaso, chamada heterogeneidade. A heterogeneidade e geralmente testada pelo teste Q ou quanticada pela estatstica I2. A investigac~ao da heterogeneidade na metanalise e de grande import^ancia pois a aus^encia ou a presenca indica o modelo estatstico mais adequado. Assim, na aus^encia desta variabilidade utilizamos um modelo estatstico de efeito xo e na presenca utilizamos um modelo de efeitos aleatorios que incorpora a variabilidade entre os estudos na metanalise. Muitas metanalises s~ao compostas por poucos estudos, e quando isso acontece, temos diculdades de estimar as medidas de efeito metanalticas atraves da teoria classica, pois esta e dependente de pressupostos assintoticos. Na abordagem bayesiana n~ao temos esse problema, mas devemos ter muito cuidado com a especicac~ao da distribuic~ao a priori. Uma vantagem da infer^encia bayesiana e a possibilidade de predizer um resultado para um estudo futuro. Neste trabalho, conduzimos um estudo sobre a especicac~ao da distribuic~ao a priori para o par^ametro que expressa a vari^ancia entre os estudos e constatamos que n~ao existe uma unica escolha que caracterize uma distribuic~ao a priori que possa ser considerada ~ao informativa\"em todas as situac~oes. A escolha de uma distribuic~ao a priori ~ao informativa\"depende da heterogeneidade entre os estudos na metanalise. Assim a distribuic~ao a priori deve ser escolhida com muito cuidado e seguida de uma analise de sensibilidade, especialmente quando o numero de estudos e pequeno. / MAZIN, S. C. Bayesian methods in meta-analysis: specication of prior distributions for the between-studies variability. 2009. 175s. Dissertation (master degree) - Faculty of Medicine of Ribeir~ao Preto, University of S~ao Paulo, Ribeir~ao Preto, 2009. Health professionals, researchers and others responsible for health policy are often overwhelmed by amounts of information that can not always be manageable, which makes the systematic review an ecient way to integrate existing knowledge generating information that may help decision making. In a systematic review, data from dierent studies can be quantitatively combined by statistical methods called meta-analysis. The meta-analysis is a statistical tool used to combine or integrate the results of several independent studies on the same topic. Among the studies that comprise the meta-analysis we have a variability that does not yield from the chance, called the heterogeneity. Heterogeneity is usually tested by Q or quantied by the statistic I2. The investigation of heterogeneity in meta-analysis has a great importance because the absence or presence indicates the most appropriate statistical model. In the absence of this variability we used a xed eect statistical model and a random eects model was used to incorporate the variability between studies in the meta-analysis. Many meta-analysis are composed of few studies, and in those cases, it is dicult to estimate the eect of meta-analytic measures by the classical theory because the asymptotic assumptions. In the Bayesian approach we do not have this problem, but we must be very careful about the specication of prior distribution. One advantage of Bayesian inference is the ability to predict an outcome for a future study. In this work, carried out a study about the specication of prior distribution for the parameter that expresses of the variance between studies and found that there is no single choice that features a prior distribution that would be considered uninformative at all times. The choice of a prior distribution uninformative depend heterogeneity among studies in the meta-analysis. Thus, the prior distribution should be examined very carefully and followed by a sensitivity analysis, especially when the number of studies is small.
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Evidenced based psychological interventions : informing best practice and considering adverse effects : Part 1. Adverse effects of psychological therapy: creation of APTMOS outcome measure based on consensus; and, Part 2. A network meta-analysis of psychological interventions for schizophrenia and psychosisMcGlanaghy, Edel January 2018 (has links)
Clinical decision-making about psychological interventions is best supported by robust evidence and informed patient choice. Randomised controlled trials (RCTs) are the current gold standard in evaluating intervention effectiveness and identifying harm. At present, RCTs of psychological intervention are unlikely to include measurement of adverse effects and this is in part due to lack of consensus about this topic. A Delphi study was conducted with a panel of both professionals and people with personal experience of face-to-face psychotherapy across the spectrum of mental health difficulties to seek consensus on what to include on a measure of adverse effects. Fifty-four items derived from an initial list of 147 items generated by the panel, are included on the APTMOS outcome measure, which now in it's preliminary form now requires validation before use in RCTs. To date, the evidence for psychological interventions for psychosis and schizophrenia has not been synthesised, which is important to inform patient choice and decision-making. Network meta-analysis compares multiple interventions using direct evidence from randomised controlled trials (RCTs) and indirect evidence from the network. A systematic review of the literature identified 91 RCTs across 23 different intervention/control group categories. Psychological interventions were more effective at reducing total symptoms of psychosis than control groups. One intervention with a low risk of bias, mindfulness-based psychoeducation, was consistently identified as most effective, with large effect sizes. Subgroup analyses identified differential effectiveness in different settings and for different subgroups. Further high quality RCT evidence of the highest ranked interventions is required to inform updates to clinical guidelines of psychological interventions for psychosis.
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The naturally restorative environment as a nonpharmacological intervention for dementiaBossen, Ann L. Gibbs 01 May 2013 (has links)
Alzheimer's disease is a form of dementia associated with disturbing and disruptive behaviors that account for many negative health and well-being outcomes, including declines in functional status, social engagement, and physical activity (Lyketsos, 2007). These behavioral consequences diminish patients' quality of life (QoL) and increase caregiver burden and the cost of care, often ultimately necessitating that patients be placed in a nursing home (Murman and Colenda, 2005).
Nature can profoundly affect people's health, well-being, and QoL; indeed, it is an old concept that the healing properties of nature can be used therapeutically. Accordingly, naturally restorative environmental (NRE) interventions stimulate one or more of the senses using natural things: elements of the earth that are living and animate, geographic, or solar and climatic (Gibson, Chalfont, Clarke, Torrington, and Sixsmith, 2007). For persons with dementia, interventions that incorporate NRE elements have demonstrated a variety of benefits, including decreased agitation; less use of psychotropic drugs); normalization of the circadian rhythm; and enhanced sociability, affect, cognitive capacity, and attention (Detweiler, Murphy, Kim, Meyers, and Ashai, 2009; Colenda, Cohen, McCall, and Rosenquist, 1997; LeGrace, 2002). Self-reported improvements in well-being, quality of life, and participation in meaningful activities have also been documented (Collins and O'Callaghan, 2008; Duggan, Blackman, Martyr, and Van Schaik, 2008; Nowak and Davis, 2011). Thus, NREs provide caregivers potential options for addressing physical, spiritual, psychological, and social needs, while at the same time, affecting behavioral responses. These widespread benefits justify further investigation and clarification.
Despite the rich potential of NRE interventions for treating dementia, the research to support NRE use has not been synthesized and defined in terms of specific behaviors that may be affected, their dosage, the optimal NRE settings, and other specific characteristics. Further research is needed to develop the most effective interventions. The purpose of this dissertation is to produce a comprehensive meta-analysis of the studies, both published and unpublished, that detail the use of NRE in interventions for behaviors and QoL in dementia care. A meta-regression was conducted of moderator variables to guide development of NRE interventions for dementia care. Additionally, the characteristics of different types of programs were synthesized. Data from thirty three articles were pooled for effect size (ES) estimates on two outcomes: disruptive behaviors and quality of life. In two-group comparisons, treatment and control, an ES = 0.484 + .138, k= 17, CI (0.215, 0.745) favored the interpretation that disruptive behaviors were attenuated with NRE interventions. Findings were higher in single, pre- post-test design studies, with an ES= 0.758+ 0.109. k= 7, CI (0.544, 0.973) for diminishing disruptive behaviors. In the two-group comparisons assessing the quality of life outcome, the ES= 0.579 + 0.171, k= 10, CI (0.243, 0.915); for single group designs, the ES= 1.347+ 0.256, k=7, CI (0.020, 0.719). Thus both design analyses indicated improved measures of QoL for persons with dementia. Moderator analysis by type of NRE, two-group design, showed statistically significant lessening in disruptive behaviors using aromatherapy, but not bright light or horticulture therapy. Better QoL was shown independently by the moderators, aromatherapy and horticulture therapy, but not bright light therapy. When single group analysis was done for each type of NRE, they all independently showed significance for both behaviors and QoL; except there were no single group designs in AT or BLT. Despite the considerable heterogeneity of the interventions, individual moderators all showed potential benefits, in a variety of settings, and in different contexts.
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CONSUMER EMBARRASSMENT – A META-ANALYTIC REVIEW AND EXPERIMENTAL EXAMINATIONZiegler, Alexander H. 01 January 2019 (has links)
This dissertation consists of two essays that discuss the influence of embarrassment on consumers. In the first essay, I examine consumers’ coping responses to embarrassment in a meta-analytic review. In essay two, I utilize an experimental approach to investigate the impact of embarrassing encounters on unrelated consumers who merely observe the situation.
In the first essay, the meta-analysis is guided by findings in the literature that demonstrate embarrassment can both promote and detract from consumer well-being. However, despite being investigated for decades, little is known about how consumers cope with embarrassing situations, and when and why consumers respond in positive and negative ways. The meta-analysis draws on the transactional framework of appraisals and coping to analyze the extant literature, construing positive responses as problem-focused coping, and negative responses as emotion-focused coping. I examine both situational and trait factor moderators to explain variance in these divergent outcomes and to resolve competing findings. A meta-analysis of 93 independent samples (N = 24,051) revealed that embarrassment leads to both problem-focused coping (r = 0.21), which can promote consumer well-being, and emotion-focused coping (r = 0.23), which can detract from consumer well-being. The relationship between embarrassment and emotion-focused coping was particularly strong in emotionally intense situations that were out of a transgressor’s control, for female consumers, and for consumers with an individualist orientation. The relationship between embarrassment and problem-focused coping was particularly strong in emotionally intense situations for male and young consumers.
The second essay investigates the influence of embarrassing situations on neutral observers of the situation. The extant literature suggests that a consumer who commits a social transgression will experience embarrassment if real or imagined others are present to witness the transgression. However, the parallel embarrassment experienced, in turn, by those observers lacks a theoretical account, since observers have committed no transgression and are not the subject of appraisal by others. I label this phenomenon observer embarrassment, and introduce perspective taking as the underlying process that leads to observer embarrassment. Across six studies, I use physiological, behavioral, and self-report measures to validate the presence of observer embarrassment, as well as the underlying perspective-taking mechanism. Specifically, the results demonstrate that observers are more likely to experience embarrassment when they imagine themselves as the transgressor (versus experience empathy for the transgressor), something more likely to occur when the observer and actor share a common identity. Thus, observer embarrassment is not an empathetic response to witnessing a social transgression, but rather an experience parallel to personal embarrassment of others.
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Validity decay versus validity stability in stem and non-stem fieldsWestrick, Paul Andrew 01 July 2012 (has links)
The main purpose of this study was to determine if validity coefficients for ACT scores, both composite scores and subject area test scores, and high school grade point average (HSGPA) decayed or held stable over eight semesters of undergraduate study in science, technology, engineering, and mathematics (STEM) fields at civilian four-year institutions, and whether the decay patterns differed from those found in non-STEM fields at the same institutions. Data from 62,212 students at 26 four-year institutions were analyzed in a hierarchical meta-analysis in which student major category (SMC), gender, and admission selectivity levels were considered potential moderators. Four sets of analyses were run. The first was by the three SMCs: STEM-Quantitative majors, STEM-Biological majors, and non-STEM majors. The second was SMC by gender. The third was SMC by admission selectivity level. The fourth was SMC by gender by admission selectivity level.
The results across all four analyses indicated that ACT score validity coefficients for STEM-Quantitative and STEM-Biological majors decayed less over eight semesters than the validity coefficients for non-STEM majors did. This was true for the uncorrected and corrected validity coefficients. For the HSGPA validity coefficients, this was true for the corrected validity coefficients. Non-STEM majors had very similar validity decay patterns regardless of the level of analysis. However, four of the eight STEM subgroups in the final set of analyses had minimal amounts of decay, and in some instances small amounts of validity growth.
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