A meta-analysis involves systematically combining results data across studies to produce a summary estimate of relative risk (or a weighted average or results). As more studies are published, more data become available that can be pooled together using a systematic approach. A meta-analysis serves many functions in a weight of evidence assessment, such as producing a weighted estimate of the magnitude of risk, examining and identifying potential sources of heterogeneity (between-study variation), evaluating the consistency of findings across studies, determining possible dose-response trends, and assessing publication bias. EpidStat epidemiologists, statisticians, and health scientists have published numerous meta-analyses on a wide variety of exposures and outcomes in top tier scientific and medical journals.
To conduct meta-analyses of randomized controlled trials (RCTs) to estimate the effect of eicosapentaenoic and docosahexaenoic acid (EPA+DHA) on coronary heart disease (CHD), and to conduct meta-analyses of prospective cohort studies to estimate the association between EPA+DHA intake and CHD risk.
A systematic literature search of Ovid/Medline, PubMed, Embase, and the Cochrane Library from January 1, 1947, to November 2, 2015, was conducted; 18 RCTs and 16 prospective cohort studies examining EPA+DHA from foods or supplements and CHD, including myocardial infarction, sudden cardiac death, coronary death, and angina, were identified. Random-effects meta-analysis models were used to generate summary relative risk estimates (SRREs) and 95% CIs. Heterogeneity was examined in subgroup and sensitivity analyses and by meta-regression. Dose-response was evaluated in stratified dose or intake analyses. Publication bias assessments were performed.
Among RCTs, there was a nonstatistically significant reduction in CHD risk with EPA+DHA provision (SRRE=0.94; 95% CI, 0.85-1.05). Subgroup analyses of data from RCTs indicated a statistically significant CHD risk reduction with EPA+DHA provision among higher-risk populations, including participants with elevated triglyceride levels (SRRE=0.84; 95% CI, 0.72-0.98) and elevated low-density lipoprotein cholesterol (SRRE=0.86; 95% CI, 0.76-0.98). Meta-analysis of data from prospective cohort studies resulted in a statistically significant SRRE of 0.82 (95% […]
Arteriovenous fistulae are the currently recommended gold standard vascular access modality for haemodialysis because of their prolonged patency, improved durability, and low risk of infection for those that mature. However, notable disadvantages are observed in terms of protracted maturation time, associated high rates of catheter use, and substantial abandonment rates. The aim of this study was to quantitatively summarize the outcomes of fistula patency, infection, maturation, and abandonment published in the scientific literature.
This was a systematic review and meta-analyses of studies evaluating fistula outcomes. Literature searches were conducted in multiple databases to identify observational and interventional studies of mean fistula patency rates at 1 year, infection risk, maturation time, and abandonment. Digitisation software was used to simulate individual patient level data from Kaplan-Meier survival plots.
Over 8000 studies were reviewed, and from these, 318 studies were included comprising 62,712 accesses. For fistulas the primary unassisted, primary assisted, and secondary patency rates at one year were 64%, 73% and 79% respectively, however not all fistulas reported as patent could be confirmed as being clinically useful for dialysis (i.e. functional patency). For fistulas that were reported as mature, mean time to maturation was 3.5 months, however only 26% of created fistulas were reported […]
The objective was to conduct a meta-analysis of studies of benzene exposure and non-Hodgkin lymphoma (NHL). A total of 8 cohort and 14 case-control studies were analyzed. Meta-analysis of any benzene exposure resulted in a summary relative risk estimate (SRRE) of 1.02 (95% CI: 0.94 to 1.12). The SRRE changed minimally when only data representing the highest level of benzene exposure were analyzed after an a priori data extraction protocol, using cumulative exposure as the optimum metric (SRRE = 1.08, 95% CI: 0.93 to 1.24). Meta-analysis of five studies that reported results for 60 or more ppm-years of cumulative exposure yielded an SRRE of 1.08 (95% CI: 0.36 to 3.24). Similarly, an SRRE of 1.04 (95% CI: 0.96 to 1.12) for each 25 ppm-year increment of benzene exposure was observed. The results from this meta-analysis are not supportive of an independent association between benzene exposure and NHL.
Alexander DD, Wagner ME. Benzene exposure and non-Hodgkin lymphoma: a meta-analysis of epidemiologic studies. J Occup Environ Med. 2010 Feb;52(2):169-89.
The relationship between red meat consumption and colorectal cancer (CRC) has been the subject of scientific debate. To estimate the summary association between red meat intake and CRC and to examine sources of heterogeneity, a meta-analysis of prospective studies was conducted. Thirty-four prospective studies of red meat and CRC were identified, of which 25 represented independent nonoverlapping study populations. Summary relative risk estimates (SRREs) for high versus low intake and dose-response relationships were calculated. In the high versus low intake meta-analysis, the SRRE was 1.12 (95% CI: 1.04-1.21) with significant heterogeneity (P=0.014). Summary associations were modified by tumor site and sex. The SRREs for colon cancer and rectal cancer were 1.11 (95% CI: 1.03-1.19) and 1.19 (95% CI: 0.97-1.46), respectively. The SRREs among men and women were 1.21 (95% CI: 1.04-1.42) and 1.01 (95% CI: 0.87-1.17), respectively. The available epidemiologic data are not sufficient to support an independent and unequivocal positive association between red meat intake and CRC. This conclusion is based on summary associations that are weak in magnitude, heterogeneity across studies, inconsistent patterns of associations across the subgroup analyses, and the likely influence of confounding by other dietary and lifestyle factors.
Alexander DD, Weed DL, Cushing CA, Lowe KA. […]