Objectives To identify and appraise empirical studies on publication and related biases published since 1998; to assess methods to deal with publication and related biases; and to examine, in a random sample of published systematic reviews, measures taken to prevent, reduce and detect dissemination bias. Data sources The main literature search, in August 2008, covered the Cochrane Methodology Register Database, MEDLINE, EMBASE, AMED and CINAHL. In May 2009, PubMed, PsycINFO and OpenSIGLE were also searched. Reference lists of retrieved studies were also examined. Review methods In Part I, studies were classified as evidence or method studies and data were extracted according to types of dissemination bias or methods for dealing with it. Evidence from empirical studies was summarised narratively. In Part II, 300 systematic reviews were randomly selected from MEDLINE and the methods used to deal with publication and related biases were assessed. Results Studies with significant or positive results were more likely to be published than those with non-significant or negative results, thereby confirming findings from a previous HTA report. There was convincing evidence that outcome reporting bias exists and has an impact on the pooled summary in systematic reviews. Studies with significant results tended to be published earlier than studies with non-significant results, and empirical evidence suggests that published studies tended to report a greater treatment effect than those from the grey literature. Exclusion of non-English-language studies appeared to result in a high risk of bias in some areas of research such as complementary and alternative medicine. In a few cases, publication and related biases had a potentially detrimental impact on patients or resource use. Publication bias can be prevented before a literature review (e.g. by prospective registration of trials), or detected during a literature review (e.g. by locating unpublished studies, funnel plot and related tests, sensitivity analysis modelling), or its impact can be minimised after a literature review (e.g. by confirmatory large-scale trials, updating the systematic review). The interpretation of funnel plot and related statistical tests, often used to assess publication bias, was often too simplistic and likely misleading. More sophisticated modelling methods have not been widely used. Compared with systematic reviews published in 1996, recent reviews of health-care interventions were more likely to locate and include non-English-language studies and grey literature or unpublished studies, and to test for publication bias. Conclusions Dissemination of research findings is likely to be a biased process, although the actual impact of such bias depends on specific circumstances. The prospective registration of clinical trials and the endorsement of reporting guidelines may reduce research dissemination bias in clinical research. In systematic reviews, measures can be taken to minimise the impact of dissemination bias by systematically searching for and including relevant studies that are difficult to access. Statistical methods can be useful for sensitivity analyses. Further research is needed to develop methods for qualitatively assessing the risk of publication bias in systematic reviews, and to evaluate the effect of prospective registration of studies, open access policy and improved publication guidelines.

The American Journal of Gastroenterology is published by Nature Publishing Group (NPG) on behalf of the American College of Gastroenterology (ACG). Ranked the #1 clinical journal covering gastroenterology and hepatology*, The American Journal of Gastroenterology (AJG) provides practical and professional support for clinicians dealing with the gastroenterological disorders seen most often in patients. Published with practicing clinicians in mind, the journal aims to be easily accessible, organizing its content by topic, both online and in print. www.amjgastro.com, *2007 Journal Citation Report (Thomson Reuters, 2008)

OBJECTIVE Glycemic variability is emerging as a measure of glycemic control, which may be a reliable predictor of complications. This systematic review and meta-analysis evaluates the association between HbA_1c variability and micro- and macrovascular complications and mortality in type 1 and type 2 diabetes. RESEARCH DESIGN AND METHODS Medline and Embase were searched (2004–2015) for studies describing associations between HbA_1c variability and adverse outcomes in patients with type 1 and type 2 diabetes. Data extraction was performed independently by two reviewers. Random-effects meta-analysis was performed with stratification according to the measure of HbA_1c variability, method of analysis, and diabetes type. RESULTS Seven studies evaluated HbA_1c variability among patients with type 1 diabetes and showed an association of HbA_1c variability with renal disease (risk ratio 1.56 [95% CI 1.08–2.25], two studies), cardiovascular events (1.98 [1.39–2.82]), and retinopathy (2.11 [1.54–2.89]). Thirteen studies evaluated HbA_1c variability among patients with type 2 diabetes. Higher HbA_1c variability was associated with higher risk of renal disease (1.34 [1.15–1.57], two studies), macrovascular events (1.21 [1.06–1.38]), ulceration/gangrene (1.50 [1.06–2.12]), cardiovascular disease (1.27 [1.15–1.40]), and mortality (1.34 [1.18–1.53]). Most studies were retrospective with lack of adjustment for potential confounders, and inconsistency existed in the definition of HbA_1c variability. CONCLUSIONS HbA_1c variability was positively associated with micro- and macrovascular complications and mortality independently of the HbA_1c level and might play a future role in clinical risk assessment.

Background: There is growing evidence that sleep duration and quality may be associated with cardiovascular harm and mortality. Methods and Results: We conducted a systematic review, meta‐analysis, and spline analysis of prospective cohort studies that evaluate the association between sleep duration and quality and cardiovascular outcomes. We searched MEDLINE and EMBASE for these studies and extracted data from identified studies. We utilized linear and nonlinear dose‐response meta‐analysis models and used DerSimonian–Laird random‐effects meta‐analysis models of risk ratios, with inverse variance weighting, and the I ² statistic to quantify heterogeneity. Seventy‐four studies including 3 340 684 participants with 242 240 deaths among 2 564 029 participants who reported death events were reviewed. Findings were broadly similar across both linear and nonlinear dose‐response models in 30 studies with >1 000 000 participants, and we report results from the linear model. Self‐reported duration of sleep >8 hours was associated with a moderate increased risk of all‐cause mortality, with risk ratio , 1.14 (1.05–1.25) for 9 hours, risk ratio, 1.30 (1.19–1.42) for 10 hours, and risk ratio, 1.47 (1.33–1.64) for 11 hours. No significant difference was identified for periods of self‐reported sleep <7 hours, whereas similar patterns were observed for stroke and cardiovascular disease mortality. Subjective poor sleep quality was associated with coronary heart disease (risk ratio , 1.44; 95% confidence interval, 1.09–1.90), but no difference in mortality and other outcomes. Conclusions: Divergence from the recommended 7 to 8 hours of sleep is associated with a higher risk of mortality and cardiovascular events. Longer duration of sleep may be more associated with adverse outcomes compared with shorter sleep durations.

Background: Radial artery occlusion ( RAO ) may occur posttransradial intervention and limits the radial artery as a future access site, thus precluding its use as an arterial conduit. In this study, we investigate the incidence and factors influencing the RAO in the current literature. Methods and Results: We searched MEDLINE and EMBASE for studies of RAO in transradial access. Relevant studies were identified and data were extracted. Data were synthesized by meta‐analysis, quantitative pooling, graphical representation, or by narrative synthesis. A total of 66 studies with 31 345 participants were included in the analysis. Incident RAO ranged between <1% and 33% and varied with timing of assessment of radial artery patency (incidence of RAO within 24 hours was 7.7%, which decreased to 5.5% at >1 week follow‐up). The most efficacious measure in reducing RAO was higher dose of heparin, because lower doses of heparin were associated with increased RAO (risk ratio 0.36, 95% CI 0.17–0.76), whereas shorter compression times also reduced RAO (risk ratio 0.28, 95% CI 0.05–1.50). Several factors were found to be associated with RAO including age, sex, sheath size, and diameter of radial artery, but these factors were not consistent across all studies. Conclusions: RAO is a common complication of transradial access. Maintenance of radial patency should be an integral part of all procedures undertaken through the radial approach. High‐dose heparin along with shorter compression times and patent hemostasis is recommended in reducing RAO .

Background—: The relationship between obstructive sleep apnea (OSA) and cardiovascular events remains unclear. We conducted a systematic review to determine the incident risk of cardiovascular events among patients with OSA. Methods and Results—: We searched MEDLINE and EMBASE in January 2011 for prospective studies that followed up patients with OSA for incident ischemic heart disease, stroke, and cardiovascular mortality. Outcomes data were pooled using random effects meta-analysis and heterogeneity assessed with the I ² statistic. Regression analysis was performed to evaluate the effects of different gradations of OSA severity based on apnea-hypopnea index. We identified 9 relevant studies from 1731 citations. OSA was associated with incident stroke in a meta-analysis of 5 studies (8435 participants), odds ratio (OR) 2.24; 95% confidence interval (CI), 1.57–3.19; I ² =7%. A significant association was seen in studies that were predominantly on men; OR, 2.87; 95% CI, 1.91–4.31, whereas data on women were sparse. In the overall analysis of 6 studies (8785 participants), OSA was nonsignificantly associated with ischemic heart disease (OR, 1.56; 95% CI, 0.83–2.91), with significant findings in the 5 studies that recruited mainly men (OR, 1.92; 95% CI, 1.06–3.48). Substantial heterogeneity was noted (I ² =74%). OSA was linked to cardiovascular death in 2 studies involving 2446 participants (OR, 2.09; 95% CI, 1.20–3.65, I ² =0%). Regression analysis showed greater likelihood of stroke or cardiovascular events with increasing apnea-hypopnea index values. Conclusions—: OSA appears to be associated with stroke, but the relationship with ischemic heart disease and cardiovascular mortality needs further research.