Umbrella Review Of Meta-analyses Research Articles

CME Exam 2: Environmental Risk Factors for Inflammatory Bowel Diseases: An Umbrella Review of Meta-analyses

CME Exam 2: Environmental Risk Factors for Inflammatory Bowel Diseases: An Umbrella Review of Meta-analyses

Elucidating the risk factors for chronic obstructive pulmonary disease: an umbrella review of meta-analyses.

Chronic obstructive pulmonary disease (COPD) is commonly attributed to smoking, and other potential risk factors are ignored. We aimed to critically appraise the epidemiological credibility of the risk factors for COPD that have been examined in published meta-analyses. We performed a systematic search to capture systematic reviews and meta-analyses of observational studies on environmental factors and biomarkers for risk of COPD. We applied a set of standardised methodological criteria based on the level of statistical significance, sample size, between-study heterogeneity and statistical biases. Our search yielded 11 eligible papers, including 18 meta-analyses on environmental factors or biomarkers for COPD risk, and eight eligible papers with systematic reviews only. Eleven associations achieved statistical significance at P < 0.001 and six associations at P < 1 × 10-6. Thirteen associations presented an I²  50%, while six associations had evidence of small-study effects and/or excess significance bias. History of tuberculosis or rheumatoid arthritis, exposure to biomass fuels, tobacco smoking and second hand smoking were supported by high epidemiological credibility for an increased risk of COPD. Furthermore, highly suggestive evidence was found for increased levels of serum C-reactive protein, and serum fibrinogen in COPD patients compared with healthy controls. To summarise, our approach suggests that, while a proportion of COPD patients are non-smokers, only a narrow range of risk factors not related to smoking have been studied for an association with COPD. There is also a need to decipher possible protective factors in COPD pathogenesis given that more than a half of ever-smokers do not develop COPD.

Risk factors for interpersonal violence: an umbrella review of meta-analyses.

Interpersonal violence is a leading cause of morbidity and mortality. The strength and population effect of modifiable risk factors for interpersonal violence, and the quality of the research evidence is not known.AimsWe aimed to examine the strength and population effect of modifiable risk factors for interpersonal violence, and the quality and reproducibility of the research evidence. We conducted an umbrella review of systematic reviews and meta-analyses of risk factors for interpersonal violence. A systematic search was conducted to identify systematic reviews and meta-analyses in general population samples. Effect sizes were extracted, converted into odds ratios and synthesised, and population attributable risk fractions (PAF) were calculated. Quality analyses were performed, including of small study effects, adjustment for confounders and heterogeneity. Secondary analyses for aggression, intimate partner violence and homicide were conducted, and systematic reviews (without meta-analyses) were summarised. We identified 22 meta-analyses reporting on risk factors for interpersonal violence. Neuropsychiatric disorders were among the strongest in relative and absolute terms. The neuropsychiatric risk factor that had the largest effect at a population level were substance use disorders, with a PAF of 14.8% (95% CI 9.0-21.6%), and the most important historical factor was witnessing or being a victim of violence in childhood (PAF = 12.2%, 95% CI 6.5-17.4%). There was evidence of small study effects and large heterogeneity. National strategies for the prevention of interpersonal violence may need to review policies concerning the identification and treatment of modifiable risk factors.Declarations of interestJ.R.G. is an NIHR Senior Investigator. The views expressed within this article are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care.

Risk factors and peripheral biomarkers for schizophrenia spectrum disorders: an umbrella review of meta-analyses.

This study aimed to systematically appraise the meta-analyses of observational studies on risk factors and peripheral biomarkers for schizophrenia spectrum disorders. We conducted an umbrella review to capture all meta-analyses and Mendelian randomization studies that examined associations between non-genetic risk factors and schizophrenia spectrum disorders. For each eligible meta-analysis, we estimated the summary effect size estimate, its 95% confidence and prediction intervals and the I2 metric. Additionally, evidence for small-study effects and excess significance bias was assessed. Overall, we found 41 eligible papers including 98 associations. Sixty-two associations had a nominally significant (P-value <0.05) effect. Seventy-two of the associations exhibited large or very large between-study heterogeneity, while 13 associations had evidence for small-study effects. Excess significance bias was found in 18 associations. Only five factors (childhood adversities, cannabis use, history of obstetric complications, stressful events during adulthood, and serum folate level) showed robust evidence. Despite identifying 98 associations, there is only robust evidence to suggest that cannabis use, exposure to stressful events during childhood and adulthood, history of obstetric complications, and low serum folate level confer a higher risk for developing schizophrenia spectrum disorders. The evidence on peripheral biomarkers for schizophrenia spectrum disorders remains limited.

Dietary Fiber Is Beneficial for the Prevention of Cardiovascular Disease: An Umbrella Review of Meta-analyses

ObjectiveThe purpose of this study was to review previously published meta-analyses on the effectiveness of dietary fiber on cardiovascular disease. MethodsAn umbrella review of all published meta-analyses was performed. A PubMed search from January 1, 1980, to January 31, 2017, was conducted using the following search strategy: (fiber OR glucan OR psyllium OR fructans) AND (meta-analysis OR systematic review). Only English-language publications that provided quantitative statistical analysis on cardiovascular disease, lipid concentrations, or blood pressure were retrieved. ResultsThirty-one meta-analyses were retrieved for inclusion in this umbrella review, and all meta-analyses comparing highest versus lowest dietary fiber intake reported statistically significant reductions in the relative risk (RR) of cardiovascular disease mortality (RR = 0.77-0.83), as well as the incidences of cardiovascular disease (RR = 0.72-0.91), coronary heart disease (RR = 0.76-0.93), and stroke (RR = 0.83-0.93). Meta-analyses on supplementation studies using β-glucan or psyllium fibers also reported statistically significant reductions in both total serum and low-density lipoprotein cholesterol concentrations. ConclusionThis review suggests that individuals consuming the highest amounts of dietary fiber intake can significantly reduce their incidence and mortality from cardiovascular disease. Mechanistically, these beneficial effects may be due to dietary fibers' actions on reducing total serum and low-density lipoprotein cholesterol concentrations between 9.3 to 14.7 mg/dL and 10.8 to 13.5 mg/dL, respectively.

Interventions for preeclampsia prevention: An umbrella review of meta-analyses of randomised trials

Interventions for preeclampsia prevention: An umbrella review of meta-analyses of randomised trials

Therapeutic benefits of glutamine: An umbrella review of meta-analyses.

Glutamine may be an essential amino acid in patients with catabolic disease, as it has been demonstrated that circulating glutamine levels drop during critical illness and following major surgery; this may result in an increase in secondary infection risk, recovery time and mortality rates. However, there is much discrepancy in the literature with regards to randomized controlled studies, and therefore, the present study is an umbrella review of published meta-analyses, conducted to examine the effectiveness of glutamine's role as a therapeutic agent. A search using PubMed, Cochrane Library and CINAHL from January 1st, 1980 to December 31st, 2016 was conducted using the following strategy: 'Glutamine AND (meta-analysis OR systematic review)' and publications were retrieved, which provided quantitative statistical analysis of pooled treatment effects on the relative risks of infectious complications, mortality and length of stay in hospital. A total of 22 meta-analyses were entered into the current umbrella review. As displayed in Tables I, II and III, these analyses are split into three groups, based on different parameters. Of the 19 meta-analyses investigating the effects of infectious complications, 15 identified statistically significant reductions in complications, with relative risks ranging between 0.42 and 0.93. In addition, 12 of the 18 meta-analyses analyzing the length of hospital stays presented statistically significant reductions in the length of stay, with reductions ranging between 0.19 to 4.73 days. Only 4 of the 15 meta-analyses studying mortality effects identified statistically significant reductions in mortality with relative risks ranging between 0.64 and 1.28. Statistically significant heterogeneity was observed in 16 of 22 meta-analyses, and publication bias was observed in five of 11 meta-analyses. Glutamine supplementation for critically ill or surgical patients through parenteral or enteral routes appears to reduce the rate of hospital acquired infectious complications and shortening of the length of stay in hospital. Furthermore, glutamine supplementation appeared to reduce the rate of in-patient mortality, but the majority of meta-analyses did not reach statistical significance. However, researchers must appreciate the positive results with caution in light of the fact that there exists statistically significant heterogeneity for the majority of meta-analyses, and statistically significant publication bias in almost half.

Effectiveness and Adverse Effects of Deep Brain Stimulation: Umbrella Review of Meta-Analyses.

Background This umbrella review summarizes the evidence across meta-analyses regarding the effectiveness and adverse effects of deep brain stimulation (DBS). Methods Databases were searched up to March 2015 for meta-analyses of comparative trials in humans assessing the effectiveness or adverse effects of DBS. Data selection, data extraction, and risk of bias assessment were performed by two independent reviewers. Results Seven eligible systematic reviews were included assessing the use of DBS for epilepsy (n = 1), obsessive-compulsive disorder (n = 1), and Parkinson disease (n = 5). The summary estimates were significant at p ≤ 0.05 in four meta-analyses (27%) with both fixed and random effects. One meta-analysis reported that DBS was more effective than sham in reducing the Yale-Brown Obsessive Compulsive Scale score in obsessive-compulsive disorder patients. The remaining three meta-analyses reported differences regarding mortality and depression in patients with Parkinson disease between DBS of the subthalamic nucleus and of the globus pallidus internus. Of the 15 meta-analyses, none compiled adequately robust evidence. Conclusions Although DBS has emerged as a viable surgical intervention to treat various disabling neurologic symptoms, existing studies fail to adequately support its use based on robust evidence without hints of bias.

Non-genetic risk factors for cutaneous melanoma and keratinocyte skin cancers: An umbrella review of meta-analyses

BackgroundSkin cancers have a complex disease mechanism, involving both genetic and non-genetic risk factors. Numerous meta-analyses have been published claiming statistically significant associations between non-genetic risk factors and skin cancers without applying a thorough methodological assessment. ObjectiveThe present study maps the literature on the non-genetic risk factors of skin cancers, assesses the presence of statistical biases and identifies the associations with robust evidence. MethodsWe searched PubMed up to January 20, 2016 to identify systematic reviews and meta-analyses of observational studies that examined associations between non-genetic factors and skin cancers. For each meta-analysis, we estimated the summary effect size by random-effects and fixed-effects models, the 95% confidence interval and the 95% prediction interval. We also assessed the between-study heterogeneity (I2 metric), evidence for small-study effects and excess significance bias. ResultsForty-four eligible papers were identified and included a total of 85 associations. Twenty-one associations were significant at P<10−6. Fifty-two associations had large or very large heterogeneity. Evidence for small-study effects and excess significance bias was found in fifteen and thirteen associations, respectively. Overall, thirteen associations (actinic keratosis, serum vitamin D, sunburns, and hair color for basal cell carcinoma and density of freckles, eye color, hair color, history of melanoma, skin type, sunburns, premalignant skin lesions, common and atypical nevi for melanoma) presented high level of credibility. ConclusionThe majority of meta-analyses on non-genetic risk factors for skin cancers suffered from large between-study heterogeneity and small-study effects or excess significance bias. The associations with convincing and highly suggestive evidence were mainly focused on skin photosensitivity and phenotypic characteristics.

Potential increased risk of cancer from commonly used medications: an umbrella review of meta-analyses

Several commonly used medications have been associated with increased cancer risk in the literature. Here, we evaluated the strength and consistency of these claims in published meta-analyses. We carried out an umbrella review of 74 meta-analysis articles addressing the association of commonly used medications (antidiabetics, antihyperlipidemics, antihypertensives, antirheumatics, drugs for osteoporosis, and others) with cancer risk where at least one meta-analysis in the medication class included some data from randomized trials. Overall, 51 articles found no statistically significant differences, 13 found some decreased cancer risk, and 11 found some increased risk (one reported both increased and decreased risks). The 11 meta-analyses that found some increased risks reported 16 increased risk estimates, of which 5 pertained to overall cancer and 11 to site-specific cancer. Six of the 16 estimates were derived from randomized trials and 10 from observational data. Estimates of increased risk were strongly inversely correlated with the amount of evidence (number of cancer cases) (Spearman's correlation coefficient = -0.77, P < 0.001). In 4 of the 16 topics, another meta-analysis existed that was larger (n = 2) or included better controlled data (n = 2) and in all 4 cases there was no statistically significantly increased risk of malignancy. No medication or class had substantial and consistent evidence for increased risk of malignancy. However, for most medications we cannot exclude small risks or risks in population subsets. Such risks are unlikely to be possible to document robustly unless very large, collaborative studies with standardized analyses and no selective reporting are carried out.