Cohort studies were found to be frequently biased by missing disease information due to death.

Objectives: In epidemiologic cohort studies with missing disease information due to death (MDID), conventional analyses right-censoring death cases at the last observation or at death may yield significant bias in relative risk and hazard ratio estimates. The aim of this study was to investigate susceptibility to this bias and assess its potential direction and magnitude.

Study Design And Setting: Literature review of selected epidemiologic, geriatric, and environmental journals in 2011-2012 and simulation study of various conventional approaches to handling missing disease data.

Systematic review finds that study data not published in full text articles have unclear impact on meta-analyses results in medical research.

Background: A meta-analysis as part of a systematic review aims to provide a thorough, comprehensive and unbiased statistical summary of data from the literature. However, relevant study results could be missing from a meta-analysis because of selective publication and inadequate dissemination. If missing outcome data differ systematically from published ones, a meta-analysis will be biased with an inaccurate assessment of the intervention effect.

Premature Discontinuation of Prospective Clinical Studies Approved by a Research Ethics Committee - A Comparison of Randomised and Non-Randomised Studies.

Background: Premature discontinuation of clinical studies affects about 25% of randomised controlled trials (RCTs) which raises concerns about waste of scarce resources for research. The risk of discontinuation of non-randomised prospective studies (NPSs) is yet unclear.

Objectives: To compare the proportion of discontinued studies between NPSs and RCTs that received ethical approval.

Treatment as Required versus Regular Monthly Treatment in the Management of Neovascular Age-Related Macular Degeneration: A Systematic Review and Meta-Analysis.

Background: To investigate whether treatment as required 'pro re nata' (PRN) versus regular monthly treatment regimens lead to differences in outcomes in neovascular age-related macular degeneration (nAMD). Regular monthly administration of vascular endothelial growth factor (VEGF) inhibitors is an established gold standard treatment, but this approach is costly. Replacement of monthly by PRN treatment can only be justified if there is no difference in patient relevant outcomes.

Extent of non-publication in cohorts of studies approved by research ethics committees or included in trial registries.

Background: The synthesis of published research in systematic reviews is essential when providing evidence to inform clinical and health policy decision-making. However, the validity of systematic reviews is threatened if journal publications represent a biased selection of all studies that have been conducted (dissemination bias). To investigate the extent of dissemination bias we conducted a systematic review that determined the proportion of studies published as peer-reviewed journal articles and investigated factors associated with full publication in cohorts of studies (i) approved by research ethics committees (RECs) or (ii) included in trial registries.