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Published Meta-analyses (published + meta-analyse)
Selected AbstractsThe relation between different dimensions of alcohol consumption and burden of disease: an overviewADDICTION, Issue 5 2010Jürgen Rehm ABSTRACT Aims As part of a larger study to estimate the global burden of disease and injury attributable to alcohol: to evaluate the evidence for a causal impact of average volume of alcohol consumption and pattern of drinking on diseases and injuries; to quantify relationships identified as causal based on published meta-analyses; to separate the impact on mortality versus morbidity where possible; and to assess the impact of the quality of alcohol on burden of disease. Methods Systematic literature reviews were used to identify alcohol-related diseases, birth complications and injuries using standard epidemiological criteria to determine causality. The extent of the risk relations was taken from meta-analyses. Results Evidence of a causal impact of average volume of alcohol consumption was found for the following major diseases: tuberculosis, mouth, nasopharynx, other pharynx and oropharynx cancer, oesophageal cancer, colon and rectum cancer, liver cancer, female breast cancer, diabetes mellitus, alcohol use disorders, unipolar depressive disorders, epilepsy, hypertensive heart disease, ischaemic heart disease (IHD), ischaemic and haemorrhagic stroke, conduction disorders and other dysrhythmias, lower respiratory infections (pneumonia), cirrhosis of the liver, preterm birth complications and fetal alcohol syndrome. Dose,response relationships could be quantified for all disease categories except for depressive disorders, with the relative risk increasing with increased level of alcohol consumption for most diseases. Both average volume and drinking pattern were linked causally to IHD, fetal alcohol syndrome and unintentional and intentional injuries. For IHD, ischaemic stroke and diabetes mellitus beneficial effects were observed for patterns of light to moderate drinking without heavy drinking occasions (as defined by 60+ g pure alcohol per day). For several disease and injury categories, the effects were stronger on mortality compared to morbidity. There was insufficient evidence to establish whether quality of alcohol had a major impact on disease burden. Conclusions Overall, these findings indicate that alcohol impacts many disease outcomes causally, both chronic and acute, and injuries. In addition, a pattern of heavy episodic drinking increases risk for some disease and all injury outcomes. Future studies need to address a number of methodological issues, especially the differential role of average volume versus drinking pattern, in order to obtain more accurate risk estimates and to understand more clearly the nature of alcohol,disease relationships. [source] Models for potentially biased evidence in meta-analysis using empirically based priorsJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES A (STATISTICS IN SOCIETY), Issue 1 2009N. J. Welton Summary., We present models for the combined analysis of evidence from randomized controlled trials categorized as being at either low or high risk of bias due to a flaw in their conduct. We formulate a bias model that incorporates between-study and between-meta-analysis heterogeneity in bias, and uncertainty in overall mean bias. We obtain algebraic expressions for the posterior distribution of the bias-adjusted treatment effect, which provide limiting values for the information that can be obtained from studies at high risk of bias. The parameters of the bias model can be estimated from collections of previously published meta-analyses. We explore alternative models for such data, and alternative methods for introducing prior information on the bias parameters into a new meta-analysis. Results from an illustrative example show that the bias-adjusted treatment effect estimates are sensitive to the way in which the meta-epidemiological data are modelled, but that using point estimates for bias parameters provides an adequate approximation to using a full joint prior distribution. A sensitivity analysis shows that the gain in precision from including studies at high risk of bias is likely to be low, however numerous or large their size, and that little is gained by incorporating such studies, unless the information from studies at low risk of bias is limited. We discuss approaches that might increase the value of including studies at high risk of bias, and the acceptability of the methods in the evaluation of health care interventions. [source] Efficacy of Aerobic Exercise on Coronary Heart Disease Risk FactorsPREVENTIVE CARDIOLOGY, Issue 2 2008George A. Kelley DA The authors examined the effects of aerobic exercise on selected coronary heart disease (CHD) risk factors using data from previously published meta-analyses. Using a random effects model, the effects of aerobic exercise on glycosylated hemoglobin (HbA1c) (mean, 95% confidence interval, ,0.9%, ,1.9% to 0.03%), resting systolic blood pressure (,6.9 mm Hg, ,9.1 to ,4.6 mm Hg), low-density lipoprotein cholesterol (,3.1 mg/dL, ,6.1 to 0 mg/dL), and body mass index (,1.3 kg/m2, ,2.5 to ,0.1 kg/m2) were either statistically significant or demonstrated a trend for statistical significance. Changes were equivalent to relative reductions of ,8.5%, ,4.7%, ,2.0%, and ,4.5%, respectively. Changes corresponded to estimated 5-year reductions in CHD mortality of 14%, 17%, 1.5%, and 5%, respectively. The results of this review reinforce the idea that aerobic exercise is an important nonpharmacologic intervention for improving selected CHD risk factors. [source] The need for patellar resurfacing in total knee arthroplasty: a literature reviewANZ JOURNAL OF SURGERY, Issue 4 2010John D. Swan Abstract The controversy over whether or not to routinely resurface the patella during a total knee arthroplasty has persisted despite three decades of successful joint replacement procedures. Advocates for routine patellar resurfacing admit the occasional need for secondary patellar resurfacing and declare increased incidence of anterior knee pain in patients with non-resurfaced patellae as a cause for worry. Surgeons that leave the patella unresurfaced cite avoidance of complications that include patellar fracture, avascular necrosis, patellar tendon injury and instability. This review discusses the available literature on patellar resurfacing through an evidence-based analysis of randomized and pseudo-randomized controlled trials and published meta-analyses to date. The published literature seems to favour resurfacing the patellar routinely. Selective patellar resurfacing would be the ideal solution if sound pre-operative criteria could be established. So far, a method for accurately predicting which patients can avoid patellar resurfacing has not been found. Future research looking at patellar resurfacing should concentrate on developing criteria for selecting those patients that would benefit from patellar resurfacing and those that would do as well without resurfacing, and thus, limiting potential surgical complications. [source] Publication bias in ecology and evolution: an empirical assessment using the ,trim and fill' methodBIOLOGICAL REVIEWS, Issue 2 2002MICHAEL D. JENNIONS ABSTRACT Recent reviews of specific topics, such as the relationship between male attractiveness to females and fluctuating asymmetry or attractiveness and the expression of secondary sexual characters, suggest that publication bias might be a problem in ecology and evolution. In these cases, there is a significant negative correlation between the sample size of published studies and the magnitude or strength of the research findings (formally the ,effect size'). If all studies that are conducted are equally likely to be published, irrespective of their findings, there should not be a directional relationship between effect size and sample size; only a decrease in the variance in effect size as sample size increases due to a reduction in sampling error. One interpretation of these reports of negative correlations is that studies with small sample sizes and weaker findings (smaller effect sizes) are less likely to be published. If the biological literature is systematically biased this could undermine the attempts of reviewers to summarise actual biology relationships by inflating estimates of average effect sizes. But how common is this problem? And does it really effect the general conclusions of literature reviews? Here, we examine data sets of effect sizes extracted from 40 peer-reviewed, published meta-analyses. We estimate how many studies are missing using the newly developed ,trim and fill' method. This method uses asymmetry in plots of effect size against sample size (,funnel plots') to detect ,missing' studies. For random-effect models of meta-analysis 38% (15/40) of data sets had a significant number of ,missing' studies. After correcting for potential publication bias, 21% (8/38) of weighted mean effects were no longer significantly greater than zero, and 15% (5/34) were no longer statistically robust when we used random-effects models in a weighted meta-analysis. The mean correlation between sample size and the magnitude of standardised effect size was also significantly negative (rs=-0.20, P < 0-0001). Individual correlations were significantly negative (P < 0.10) in 35% (14/40) of cases. Publication bias may therefore effect the main conclusions of at least 15,21% of meta-analyses. We suggest that future literature reviews assess the robustness of their main conclusions by correcting for potential publication bias using the ,trim and fill' method. [source] | ||||||||||