BACKGROUND: Causal mediation analysis is often used to understand the impact of variables along the causal pathway of an occurrence relation. How well studies apply and report the elements of causal mediation analysis remains unknown. METHODS: We systematically reviewed epidemiological studies published in 2015 that employed causal mediation analysis to estimate direct and indirect effects of observed associations between an exposure on an outcome. We identified potential epidemiological studies through conducting a citation search within Web of Science and a keyword search within PubMed. Two reviewers independently screened studies for eligibility. For eligible studies, one reviewer performed data extraction, and a senior epidemiologist confirmed the extracted information. Empirical application and methodological details of the technique were extracted and summarized. RESULTS: Thirteen studies were eligible for data extraction. While the majority of studies reported and identified the effects of measures, most studies lacked sufficient details on the extent to which identifiability assumptions were satisfied. Although most studies addressed issues of unmeasured confounders either from empirical approaches or sensitivity analyses, the majority did not examine the potential bias arising from the measurement error of the mediator. Some studies allowed for exposure-mediator interaction and only a few presented results from models both with and without interactions. Power calculations were scarce. CONCLUSIONS: Reporting of causal mediation analysis is varied and suboptimal. Given that the application of causal mediation analysis will likely continue to increase, developing standards of reporting of causal mediation analysis in epidemiological research would be prudent.

BACKGROUND: Little research has been conducted into the physical health implications of suicide bereavement compared to other causes of death. There is some evidence that suicide bereaved parents have higher morbidity, particularly in terms of chronic illness. This systematic review aims to examine the physical and psychosomatic morbidities of people bereaved by a family member's suicide and compare them with family members bereaved by other modes of death. METHODS: MEDLINE, EMBASE, CINAHL, and PsycINFO were searched from 1985 to February 2016. The search was re-run in March 2017. Peer-reviewed English language articles comparing suicide-bereaved family members to non-suicide bereaved family members on measures of physical or psychosomatic health were eligible for inclusion. Cohort, cross-sectional, case-control and cohort-based register studies were eligible for inclusion. A modified version of the Newcastle Ottawa Scale was used for quality assessment. Results were synthesised using narrative synthesis. RESULTS: The literature search located 24 studies which met the inclusion criteria. Seven studies found statistically significant associations between physical health and suicide bereavement. Five of the studies found that suicide-bereaved family members were more likely to experience pain, more physical illnesses and poorer general health. They were also at increased risk of cardiovascular disease, hypertension, diabetes and chronic obstructive pulmonary disease. In contrast, another study in Denmark found that those bereaved by suicide had a lower risk of a number of physical health disorders, including cancers, diabetes, cardiovascular and chronic lower respiratory tract disorders compared to those bereaved by other causes of death. Additionally, a further study conducted in the United States found that suicide-bereaved children visited a GP less frequently than non-suicide bereaved children. CONCLUSIONS: Review findings are relevant for clinicians working with people bereaved by suicide as they highlight that such clients are at increased risk of several adverse physical health outcomes. Future research should examine health risk behaviours of suicide-bereaved and non-suicide bereaved family members as they may confound the association between exposure and outcome. TRIAL REGISTRATIONS: The review protocol has been registered on PROSPERO, registration number CRD42016030007 .

To perform a systematic review of studies prospectively analyzing the impact of regionalization of complex surgical oncology care on patient outcomes. High volume care of complex surgical oncology patients has been repeatedly associated with improved outcomes. Most studies, however, are retrospective and have not prospectively accounted for confounders such as financial ability and social support. Four electronic databases (Ovid MEDLINE(R), Ovid EMBASE, Cochrane Library (Wiley), and EBSCHOHost) were searched from inception until August 25, 2018. Two authors independently reviewed 5887 references, with a third independent reviewer acting as arbitrator when needed. Data extracted from 11 articles that met inclusion criteria. Risk of bias assessments conducted using MINORS criteria for the non-randomized, observational studies, and the Cochrane tool for the randomized-controlled trial. Of the 11 studies selected, we found 7 historically-controlled trials, two retrospective cohort studies with prospective data collection, one prospective study, and one randomized-controlled trial. 73% of studies were from Northern Europe, 18% from Ontario, Canada, and 9% from England. Pancreatic surgery accounted for 36% of studies, followed by gynecologic oncology (27%), thoracic surgery (18%), and dermatologic surgery (9%). The studies reported varying outcome parameters, but all showed improvement post-regionalization. Included studies featured poor-to-fair risk of bias. 11 studies indicated improved outcomes following regionalization of surgical oncology, but most exhibit poor methodological rigor. Prospective evidence for the regionalization of surgical oncology is lacking. More research addressing patient access to care and specialist availability is needed to understand the shortcomings of centralization.