Further analysis of a meta-analysis.
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Meta-analysis in epidemiology.
Meta-analysis is the structured and systematic qualitative and quantitative integration of the results of several independent studies (i.e. the epidemiology of results). As in any epidemiological study, a meta-analysis needs to start with clearly stated aims and objectives. Attention needs to be paid to selection bias in selecting the study population (all publications on the topic). An initial qualitative assessment (conducted blinded to results) categorises projects on the basis of their methods, as unacceptable (dropped from later analysis) and acceptable or good. Further analysis could be conducted by stratifying or weighting independent studies according to preset quality criteria. The quantitative assessment involves deriving a pooled measure of outcome (usually the relative or attributable risk). Tests for heterogeneity are required before pooling. By pooling the results from many settings using different methods, the ability to generalise them in terms of their public health relevance is increased.
Meta-Analysis as Topic↗
Meta-analysis and evidence.
Meta-analysis is the science of combining evidence from different studies, but traditional statistical techniques contain neither a formal definition nor a measure of evidence. It is argued in this paper that the log-likelihood ratio, as a measure of the "weight of evidence," can be a very useful tool in the meta-analysis. The mathematics and the philosophy behind the use of this index are introduced. The construction and interpretation of "support curves" in fixed and random-effects models are presented. The application of evidential techniques is illustrated on six trials of aspirin therapy previously presented by Canner. The possible dangers of focusing on statistical error rates instead of evidence are discussed.
Aspirin↗
Meta-analysis techniques.
The three elements of meta-analysis include exact specification of sources from which primary studies are identified; transformation of primary study findings to a common metric; and statistical analysis of primary study findings. Meta-analysis has several drawbacks, such as dependence on the quality of the reporting of primary analysis findings; dependence on sufficient numbers of eligible studies to justify statistical analysis; a lack of a universal common metric; and a lack of expert agreement about the best form of statistical analysis. As researchers become more familiar with meta-analysis, two effects will be seen: an increased use of meta-analysis elements in all review of literature, and increased attention to reporting important details of research in scientific journals.
Humans↗
Early enteral feeding, compared with parenteral, reduces postoperative septic complications. The results of a meta-analysis.
This two-part meta-analysis combined data from eight prospective randomized trials designed to compare the nutritional efficacy of early enteral (TEN) and parenteral (TPN) nutrition in high-risk surgical patients. The combined data gave sufficient patient numbers (TEN, n = 118; TPN, n = 112) to adequately address whether route of substrate delivery affected septic complication incidence. Phase I (dropouts excluded) meta-analysis confirmed data homogeneity across study sites, that TEN and TPN groups were comparable, and that significantly fewer TEN patients experienced septic complications (TEN, 18%; TPN, 35%; p = 0.01). Phase II meta-analysis, an intent-to-treat analysis (dropouts included), confirmed that fewer TEN patients developed septic complications. Further breakdown by patient type showed that all trauma and blunt trauma subgroups had the most significant reduction in septic complications when fed enterally. In conclusion, this meta-analysis attests to the feasibility of early postoperative TEN in high-risk surgical patients and that these patients have reduced septic morbidity rates compared with those administered TPN.
Adult↗
Dipyridamole in the treatment of angina pectoris: a meta-analysis.
A meta-analysis was performed to reevaluate the efficacy of dipyridamole for prophylaxis of angina pectoris. We found 10 articles that reported 11 randomized control trials published between 1960 and 1970. Three trials found a statistically significant benefit for the drug vs placebo, four showed a positive trend, two found no difference, and two showed a slight trend favoring placebo. When the results of all 11 trials were combined, two different statistical methods showed a statistically significant benefit from the drug. These combined results must be interpreted cautiously because of excluded patients and other methodologic variations in the studies, as well as evidence from other studies that dipyridamole may aggravate angina. Nevertheless, we conclude that there is some evidence for efficacy of the drug and believe the question should be restudied in larger and better-designed trials.
Angina Pectoris↗
The dissemination of research findings: some limitations revealed when attempting a meta-analysis.
A meta-analysis of the literature on drug treatments for Alzheimer's disease revealed the following limitations in the dissemination of research findings: multiple publication of findings, failure to report basic descriptive statistics and failure to respond to written requests for additional information on the research. The possible reasons for these problems and remedies for them are discussed.
Alzheimer Disease↗
Meta-analysis in clinical research.
Meta-analysis is the process of combining study results that can be used to draw conclusions about therapeutic effectiveness or to plan new studies. We review important design and statistical issues of this process. The design issues include protocol development, objectives, literature search, publication bias, measures of study outcomes, and quality of the data. The statistical issues include consistency (homogeneity) of study outcomes, and techniques for pooling results from several studies. Guidelines are provided to assess the quality of meta-analyses based on our discussion of the design and statistical issues. Limitations and areas for further development of this approach are discussed; researchers should come to a general agreement on how to conduct meta-analysis. As an explicit strategy for summarizing results, meta-analysis may help clinicians and researchers better understand the findings of clinical studies.
Data Collection↗
The impact of methodological factors on child psychotherapy outcome research: a meta-analysis for researchers.
Two recent meta-analyses have generated evidence for child and adolescent psychotherapy effects. However, critics note that such meta-analyses often include studies with methodological shortcomings which might invalidate their results. In the present study, we explored whether the results of the most extensive child/adolescent meta-analysis might have been influenced by such methodological variables, focusing on internal validity and external validity factors. Together, these factors accounted for two-thirds as much variance as the substantive factors (e.g., type of therapy, age) in the original meta-analysis. This suggests that relative to these therapy and child-characteristic variables, methodological factors have a substantial, though smaller, impact on meta-analysis results. In general, increased experimental rigor was related to larger effect sizes; this argues against the hypothesis that methodologically weak studies have led to an overestimate of therapy effects. No significant interactive relations were found between validity factors and predictors of outcome; this suggests that the relations noted in previous meta-analyses between outcome and various variables were not distorted by the validity factors tested here.
Adaptation, Psychological↗
A prototype for integrative review and meta-analysis of nursing research.
Meta-analysis has gained international recognition as a statistical approach to research synthesis. What is missing in research reviews, however, is the systematic compilation of results from non-experimentally designed studies. An approach is described which extends the rigours of integrative research review and meta-analysis to descriptive studies. A model for conceptualizing a systematically derived research synthesis is presented with selected accompanying generic elements. The model serves as a prototype for application to a variety of topical areas of interest. Generic elements contained in the prototype may be tailored to specific topics with relative ease. Resources and time required for topic development from conceptualization through to dissemination can be considerably reduced by adaptation of the generic elements.
Clinical Nursing Research↗
Informing the mammography coverage debate. Results of meta-analysis, computer modeling, and issue analysis.
Methods of meta-analysis, computer modeling, and issue analysis are used to answer four key questions related to efficacy, cost, and political feasibility of legislating insurance coverage for mammography. The findings are presented, and the strengths and weaknesses of the combined use of these methods to inform policy debate at the regional level are discussed.
Adult↗
How effective are current drugs for Crohn's disease? A meta-analysis.
We have conducted a meta-analysis of 12 placebo controlled trials to determine the efficacy of single drug therapy in Crohn's disease for both induction (seven trials) and maintenance (five trials) of remission. A total of 767 and 796 patients were studied, respectively. Various clinical criteria of success were analyzed. The Dersimonian-Laird method for meta-analysis was used to calculate the risk difference (RD). Therapeutic advantage, defined as the difference between drug and placebo response, was also determined. Using various criteria of success, we found that single drug therapy conferred an 11-29% therapeutic advantage (RD = 0.13-0.33) over placebo for the induction of remission. In trials for maintenance, no therapeutic advantage was found for single drug therapy over placebo. All forms of maintenance therapy followed nearly identical linear rates of relapse over time, showing an approximately 90% maintenance of remission rate at 3 months, which decreased to 25% at 36 months. In conclusion, meta-analysis has established a standard of reference against which future drug trials can be compared. This standard of reference for drug and placebo rates, as well as the corresponding risk differences and therapeutic advantages can help determine the relative value of newer agents in the therapy of Crohn's disease.
Crohn Disease↗
Cigarette smoking-associated changes in blood lipid and lipoprotein levels in the 8- to 19-year-old age group: a meta-analysis.
In this meta-analysis it was demonstrated that, when compared with nonsmokers of similar age, smokers in the 8- to 19-year-old age group have significantly higher serum levels of triglyceride (+11.8%), very-low-density lipoprotein (VLDL)-cholesterol (+12.4%) and low-density lipoprotein (LDL)-cholesterol (+4.1%) and significantly lower serum levels of high-density lipoprotein (HDL)-cholesterol (-8.5%) and total cholesterol (-3.7%). All of these smoking-associated changes are in the same direction as those found in adults, with the exception of total cholesterol levels, which are significantly increased in adult smokers. The extent to which mean triglyceride, LDL-cholesterol, and HDL-cholesterol levels are shifted is significantly greater in the 8- to 19-year-old smokers than in adult smokers. The changes in mean total cholesterol levels among smokers in both age groups represent only the net shifts in the lipoprotein fractions and are therefore likely to be a less sensitive indicator of the possible lipid-related excess coronary artery disease risk in smokers.
Adolescent↗
Socioeconomic differences in the effectiveness of oral health programs for dental caries prevention in Europe: A systematic review and meta-analysis.
AIM: The meta-analysis systematically summarized evidence on how socioeconomic status (SES), access to dental care, and oral health programs (OHP) affect caries prevalence and severity among children and adults in Europe. METHODS: Four electronic databases (PubMed, Scopus, Cochrane Library and Embase) were systematically screened from 1947-2026, supplemented by cross-referencing and manual searches, without language restrictions. Study selection, data extraction and quality assessment were done in duplicate. Methodological quality was assessed using the NHLBI Study Quality Assessment Tools according to study design. Certainty of evidence was graded using GRADE Profiler 3.6. Mean differences (MD) were calculated for changes in DMFT, and odds ratios (OR) for the presence of dental caries in individuals using fixed-or random-effects models. RESULTS: Electronic searching identified 1800 articles; 23 studies were included in the review (>169,000 participants) and 14 in the meta-analyses (>88,000). Nine studies evaluated the effectiveness of OHP stratified by SES, and ten examined OHP in low-SES populations. Among low-SES individuals, participation in OHP was associated with a significantly lower increase in DMFT (MD[95% CI]=-0.63[-0.94;-0.31];very low certainty) and significantly lower odds of having dental caries (OR[95% CI]=0.61[0.52;0.73];very low) compared with non-participation. Among program participants, individuals with low SES showed a significantly greater increase in DMFT than those with high SES (MD[95% CI]=0.79[0.30;1.21];very low) and had significantly higher odds of having dental caries (OR[95% CI]= 2.88[1.97;4.22];very low). CONCLUSION: Participation in OHP may be associated with reducing dental caries in European populations, but benefits are unequally distributed and increase with higher SES. However, this conclusion is based on a limited number of well-conducted trials.
Humans↗
Meta-analysis: whither narrative review?
Meta-analysis refers to methodologies that are used to integrate related empirical research to arrive at conclusions not possible by reviewing individual studies, or to improve generalizations of individual studies. It is distinguished from the traditional narrative review in that statistical methodologies are applied to derive more objective conclusions than those that typify narrative reviews. Meta-analysis has been slow to appear in the literature of clinical medicine, however, particularly when viewed in the context of the exponential expansion of literature and the availability of computer technology to facilitate its conduct.
Clinical Medicine↗
[Ginkgo biloba extract in peripheral arterial diseases. Meta-analysis of controlled clinical studies].
In the first part the statistical methods of meta-analysis are discussed. Meta-analysis is considered as a statistical tool for quantitatively summarizing the results of clinical trials with comparable aims (treatments) and designs. Meta-analysis can be based on the significance probabilities or effect values. The last procedure is preferable as it gives an estimate (and confidence interval) for the global effect of the treatment of interest, if homogeneity of the effects between the trials can be assumed. Such a homogeneity can be often achieved by a suitable standardization of the effect variables within the trials. In the second part the methods of meta-analysis are applied to controlled clinical trials with Ginkgo biloba extract EGb 761 in patients with peripheral arterial disease. Included were 5 placebo-controlled clinical trials with similar design and inclusion criteria. In all studies treatment effect was quantified by the increase of walking distance (measured in standardized treadmill exercise). The effect value of EGb 761 treatment was expressed by the standardized mean difference in walking distance increase between EGb 761 and placebo, standardized by the standard deviation. It could be shown that this effect value is homogeneous in all trials. The global effect size was estimated as 0.75. This means that the mean increase in walking distance achieved by EGb 761 is 0.75 times of the standard deviation higher than that achieved by placebo. This value is highly significant different from zero. So the meta-analysis revealed a highly significant therapeutic effect of EGb 761 for the treatment of peripheral arterial disease.
Arteries↗
The Impact of Nutritional Status on Oral Health Outcomes and Management in Older Adults: A Systematic Review and Meta-Analysis.
OBJECTIVE: This systematic review and meta-analysis evaluated the relationship between nutritional status and the oral health of older adults (aged 75 years or older). The PECO focus question was, 'What is the occurrence, association and impact of nutritional state on the oral health outcomes and its management in older adults?' METHODS: A comprehensive literature search was performed across MEDLINE (PubMed), Embase and the Cochrane Library. Publications up to April 2025 were considered, yielding 3324 records for initial screening. Quality assessment of the included studies predominantly revealed a low to moderate risk of bias. RESULTS: Eighty-three studies were included for data analysis. Meta-analyses demonstrated that older adults at risk of malnutrition had fewer teeth (SMD = -0.29; 95% CI: -0.46, -0.11; p = 0.002). Those with < 20 teeth and who were not rehabilitated with dentures were more likely to be malnourished (OR = 4.00; 95% CI: 1.21, 13.18; p = 0.02). Malnutrition was associated with self-reported chewing problems (OR = 2.38; 95% CI: 1.74, 3.26; p < 0.0001), swallowing problems (OR = 3.18; 95% CI: 2.20, 4.61; p < 0.0001) or dry mouth (OR = 2.35; 95% CI: 1.91, 2.88; p < 0.0001). Conversely, those with oral pain showed lower odds of malnutrition risk (OR = 0.68; 95% CI: 0.52, 0.89; p = 0.005). CONCLUSIONS: Fewer teeth, existing chewing or swallowing problems, dry mouth and the absence of removable dentures where needed, were associated with malnutrition in care-dependent older adults. The current lack of longitudinal studies and proof of causality for malnutrition affecting oral health outcomes underscores the need for further research to better clarify the complex relationship between oral health and nutrition in older populations. TRIAL REGISTRATION: PROSPERO Registration: CRD420251003549.
Humans↗
Meta-analysis for descriptive research.
Although nurses have begun to use meta-analysis, a review of the nursing literature demonstrates that its use has not been maximized. Meta-analysis can be employed to synthesize descriptive as well as experimental research, yet attention in nursing has focused almost exclusively on meta-analysis techniques for, and meta-analytic studies of, experimental research. Furthermore, nursing literature has emphasized use of the effect size index (d) rather than the correlation index (r); the latter may, in some cases, be the more suitable metric, particularly with meta-analysis of correlational studies. An argument is made for the value of meta-analysis as a technique for integrating descriptive research, and an overview of different meta-analytic approaches to data analysis using the correlational index with descriptive research is provided.
Humans↗