Showing papers by "Allan Donner published in 2012"

Shift work and vascular events: systematic review and meta-analysis

Abstract: Objective To synthesise the association of shift work with major vascular events as reported in the literature. Data sources Systematic searches of major bibliographic databases, contact with experts in the field, and review of reference lists of primary articles, review papers, and guidelines. Study selection Observational studies that reported risk ratios for vascular morbidity, vascular mortality, or all cause mortality in relation to shift work were included; control groups could be non-shift (“day”) workers or the general population. Data extraction Study quality was assessed with the Downs and Black scale for observational studies. The three primary outcomes were myocardial infarction, ischaemic stroke, and any coronary event. Heterogeneity was measured with the I 2 statistic and computed random effects models. Results 34 studies in 2 011 935 people were identified. Shift work was associated with myocardial infarction (risk ratio 1.23, 95% confidence interval 1.15 to 1.31; I 2 =0) and ischaemic stroke (1.05, 1.01 to 1.09; I 2 =0). Coronary events were also increased (risk ratio 1.24, 1.10 to 1.39), albeit with significant heterogeneity across studies (I 2 =85%). Pooled risk ratios were significant for both unadjusted analyses and analyses adjusted for risk factors. All shift work schedules with the exception of evening shifts were associated with a statistically higher risk of coronary events. Shift work was not associated with increased rates of mortality (whether vascular cause specific or overall). Presence or absence of adjustment for smoking and socioeconomic status was not a source of heterogeneity in the primary studies. 6598 myocardial infarctions, 17 359 coronary events, and 1854 ischaemic strokes occurred. On the basis of the Canadian prevalence of shift work of 32.8%, the population attributable risks related to shift work were 7.0% for myocardial infarction, 7.3% for all coronary events, and 1.6% for ischaemic stroke. Conclusions Shift work is associated with vascular events, which may have implications for public policy and occupational medicine.

Closed-form confidence intervals for functions of the normal mean and standard deviation.

Abstract: Confidence interval methods for a normal mean and standard deviation are well known and simple to apply. However, the same cannot be said for important functions of these parameters. These functions include the normal distribution percentiles, the Bland-Altman limits of agreement, the coefficient of variation and Cohen's effect size. We present a simple approach to this problem by using variance estimates recovered from confidence limits computed for the mean and standard deviation separately. All resulting confidence intervals have closed forms. Simulation results demonstrate that this approach performs very well for limits of agreement, coefficients of variation and their differences.

What is the role and authority of gatekeepers in cluster randomized trials in health research

Abstract: This article is part of a series of papers examining ethical issues in cluster randomized trials (CRTs) in health research. In the introductory paper in this series, we set out six areas of inquiry that must be addressed if the CRT is to be set on a firm ethical foundation. This paper addresses the sixth of the questions posed, namely, what is the role and authority of gatekeepers in CRTs in health research? ‘Gatekeepers’ are individuals or bodies that represent the interests of cluster members, clusters, or organizations. The need for gatekeepers arose in response to the difficulties in obtaining informed consent because of cluster randomization, cluster-level interventions, and cluster size. In this paper, we call for a more restrictive understanding of the role and authority of gatekeepers. Previous papers in this series have provided solutions to the challenges posed by informed consent in CRTs without the need to invoke gatekeepers. We considered that consent to randomization is not required when cluster members are approached for consent at the earliest opportunity and before any study interventions or data-collection procedures have started. Further, when cluster-level interventions or cluster size means that obtaining informed consent is not possible, a waiver of consent may be appropriate. In this paper, we suggest that the role of gatekeepers in protecting individual interests in CRTs should be limited. Generally, gatekeepers do not have the authority to provide proxy consent for cluster members. When a municipality or other community has a legitimate political authority that is empowered to make such decisions, cluster permission may be appropriate; however, gatekeepers may usefully protect cluster interests in other ways. Cluster consultation may ensure that the CRT addresses local health needs, and is conducted in accord with local values and customs. Gatekeepers may also play an important role in protecting the interests of organizations, such as hospitals, nursing homes, general practices, and schools. In these settings, permission to access the organization relies on resource implications and adherence to institutional policies.

Quality of cluster randomized controlled trials in oral health: a systematic review of reports published between 2005 and 2009

Abstract: – Objectives: To assess the quality of methods and reporting of recently published cluster randomized trials (CRTs) in oral health. Methods: We searched PubMed for CRTs that included at least one oral health-related outcome and were published from 2005 to 2009 inclusive. We developed a list of criteria for assessing trial quality and reporting. This was influenced largely by the extended CONSORT statement for CRTs but also included criteria suggested by other authors. We examined the extent to which trials were consistent with these criteria. Results: Twenty-three trials were included in the review. In 15 (65%) trials, clustering had been accounted for in sample size calculations, and in 18 (78%) authors had accounted for clustering in analysis. Intraclass correlation coefficients (ICCs) were reported for eight (35%) trials; the outcome assessor was reported as having been blinded to allocation in 12 (52%) trials; 17 (74%) described eligibility criteria at individual level, but only nine (39%) described such criteria at cluster level. Sixteen of 20 trials (80%), in which individuals were recruited, reported that individual informed consent was obtained. Conclusions: These results suggest that the quality of recent CRTs in oral health is relatively high and appears to compare favourably with other fields. However, there remains room for improvement. Authors of future trials should endeavour to ensure sample size calculations and analyses properly account for clustering (and are reported as such), consider the potential for recruitment/identification bias at the design stage, describe the steps taken to avoid this in the final report and report observed ICCs and cluster-level eligibility criteria.

Cluster-randomized trial of early palliative care for patients with metastatic cancer.

Abstract: 9003 Background: Patients with metastatic cancer have compromised quality of life (QOL), which tends to worsen towards the end of life. We conducted a cluster-randomized trial of early versus routi...

Evidence-based sample size estimation based upon an updated meta-regression analysis.

Abstract: A traditional meta-analysis examines the overall effectiveness of an intervention by producing a pooled estimate of treatment efficacy. In contrast to this, a meta-regression model seeks to determine whether a study-level covariate (X) is a plausible source of heterogeneity in a set of treatment effects. Upon performing such an analysis, the results may suggest the presence of a meaningful amount of variation in the treatment effects because of the covariate; however, the current set of trials may not provide sufficient statistical power for such a conclusion. The proposed approach provides quantitative insight into the amount of support that a new trial may provide to the hypothesis that X is a meaningful source of variation in an updated meta-regression model, which includes both the previously completed and the proposed trial. This empirical algorithm allows examination of the potential feasibility of a planned study of various sizes to further support or refute the hypothesis that X is a statistically significant source of variation. A detailed example illustrates the sample size estimation algorithm for both a planned individually or cluster randomized trial to investigate the now commonly accepted impact of geographical latitude on the observed effectiveness of the Bacillus Calmette-Guerin vaccine in the prevention of tuberculosis. Copyright © 2012 John Wiley & Sons, Ltd.

Measures of family resemblance for binary traits: likelihood based inference.

Abstract: Detection and estimation of measures of familial aggregation is considered the first step to establish whether a certain disease has genetic component. Such measures are usually estimated from observational studies on siblings, parent-offspring, extended pedigrees or twins. When the trait of interest is quantitative (e.g. Blood pressures, body mass index, blood glucose levels, etc.) efficient likelihood estimation of such measures is feasible under the assumption of multivariate normality of the distributions of the traits. In this case the intra-class and inter-class correlations are used to assess the similarities among family members. When the trail is measured on the binary scale, we establish a full likelihood inference on such measures among siblings, parents, and parent-offspring. We illustrate the methodology on nuclear family data where the trait is the presence or absence of hypertension.