meta-analysis


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meta-analysis

a method by which the results of a number of quantitative studies can be analysed together to produce an overall impression from a field of research. This method lays emphasis on EFFECT SIZE as well as providing a SIGNIFICANCE TEST for the results. It has advantages over a conventional review in that it forces the analyst to evaluate the method and the results of a study more critically and that it provides an objective method for synthesizing the results from such studies. There are two basic approaches to meta-analysis. The first and most common approach involves combining the results from the studies in order to produce a single effect size, inferential statistic and probability. The second approach involves comparing studies which differ over some aspect of their method to see if the results of studies which utilized one design or measure differ from the results of studies employing a different design or method. By combining the results of a number of studies, meta-analysis can circumvent the problems of low STATISTICAL POWER which may characterize the individual studies. (See Cooper; 1998; Cooper and Hedges, 1994; Rosenthal, 1991)
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Inadequate reporting of key information in meta-analyses limits researchers' and clinicians' ability to critically appraise and independently interpret meta-analysis results, and therefore diminishes their clinical values.
Studies were included in this umbrella review if they met all of the following criteria: (1) systematic review including meta-analysis (quantitative analysis) of RCTs, crossover, and observational studies; (2) garlic supplementation; garlic intake; highest vs.
Comment: The results of this meta-analysis suggest that omega-3 fatty acids are beneficial in the treatment of dry eye syndrome.
Meta-analysis, then, can provide answers to the most important questions in program planning and prevention: What works?
KEY WORDS: Meta-analysis, network meta-analysis, indirect comparison, direct estimates, indirect estimates
It is the first meta-analysis to pool results from studies of blood cytokine levels in outpatients with three serious mental illnesses, Dr.
* The evidence analyzed in the Sgolastra et al meta-analysis indicates that Nd:YAG+SRP has potential for benefits beyond SRP alone due to the reduction in PD and GCF; however, the low number of studies eligible for inclusion and the risk of bias for studies included leads to the conclusion that insufficient evidence exists to support the effectiveness of Nd:YAG adjunctive to SRP.
Meta-analysis of subgroups showed a significant reduction in systolic BP in hypertensive (-4.4 mm Hg; 95% Cl, -7.37 to -1.42, 12=0.0%; P=.004) but not normotensive patients.
The a priori inclusion criteria for this study were as follows: (1) previous systematic reviews with meta-analysis of randomized controlled trials or data reported separately for randomized controlled trials, (2) children and adolescents 5 to 18 years of age, (3) aerobic exercise and/or progressive resistance training intervention(s) lasting for an average of at least 4 weeks, (4) published and unpublished (dissertations and master's theses) studies in any language from 1990 forward, and (5) exercise minus control group difference in one or more of the following variables that were primary outcomes in the original meta-analysis: body weight, body mass index, body mass index percentile, body mass index z-score, percent body fat, fat mass, and fat-free mass.
Conducting meta-analysis in R with the metafor package.
A meta-analysis normally uses the same principles as a systematic literature review, but pools quantitative results.