Le rôle des attributions dans la relation entre l'environnement socio-professionnel et le niveau habituel d'estime de soi : le cas des serveuses de bar

Québec Université Laval, Bibliothèque 201

3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase Inhibitors and the Risk of Cancer

Background During the past 15 years there has been an exponential increase in the number of prescriptions for lipid-lowering drugs. Uncertainties remain about the long-term impact of these medications on cancer, which is particularly bothersome given that the duration of these treatments may extend for several decades.\ud Objective To explore the association between 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors and cancer incidence.\ud Methods Using the administrative health databases of the Régie de l'Assurance-Maladie du Québec we performed a nested case-control study. We selected a cohort of 6721 beneficiaries of the health care plan of Quebec who were free of cancer for at least 1 year at cohort entry, 65 years and older, and treated with lipid-modifying agents. Cohort members were selected between 1988 and 1994 and were followed up for a median period of 2.7 years. From the cohort, 542 cases of first malignant neoplasm were identified, and 5420 controls were randomly selected. Users of HMG-CoA reductase inhibitors were compared with users of bile acid–binding resins as to their risk of cancer. Specific cancer sites were also considered.\ud Results Users of HMG-CoA reductase inhibitors were found to be 28% less likely than users of bile acid–binding resins to be diagnosed as having any cancer (rate ratio, 0.72; 95% confidence interval, 0.57-0.92). All specific cancer sites under study were found to be not or inversely associated with the use of HMG-CoA reductase inhibitors.\ud Conclusion The results of our study provide some degree of reassurance about the safety of HMG-CoA reductase inhibitors

Understanding and diagnosing the potential for bias when using machine learning methods with doubly robust causal estimators

Data-adaptive methods have been proposed to estimate nuisance parameters when using doubly robust semiparametric methods for estimating marginal causal effects. However, in the presence of near practical positivity violations, these methods can produce a separation of the two exposure groups in terms of propensity score densities which can lead to biased estimates of the treatment effect. To motivate the problem, we evaluated the Targeted Minimum Loss-based Estimation procedure using a simulation scenario to estimate the average treatment effect. We highlight the divergence in estimates obtained when using parametric and data-adaptive methods to estimate the propensity score. We then adapted an existing diagnostic tool based on a bootstrap resampling of the subjects and simulation of the outcome data in order to show that the estimation using data-adaptive methods for the propensity score in this study may lead to large bias and poor coverage. The adapted bootstrap procedure is able to identify this instability and can be used as a diagnostic tool

Impact of discretization of the timeline for longitudinal causal inference methods

In longitudinal settings, causal inference methods usually rely on a discretization of the patient timeline that may not reflect the underlying data generation process. This paper investigates the estimation of causal parameters under discretized data. It presents the implicit assumptions practitioners make but do not acknowledge when discretizing data to assess longitudinal causal parameters. We illustrate that differences in point estimates under different discretizations are due to the data coarsening resulting in both a modified definition of the parameter of interest and loss of information about time-dependent confounders. We further investigate several tools to advise analysts in selecting a timeline discretization for use with pooled Longitudinal Targeted Maximum Likelihood Estimation for the estimation of the parameters of a marginal structural model. We use a simulation study to empirically evaluate bias at different discretizations and assess the use of the cross-validated variance as a measure of data support to select a discretization under a chosen data coarsening mechanism. We then apply our approach to a study on the relative effect of alternative asthma treatments during pregnancy on pregnancy duration. The results of the simulation study illustrate how coarsening changes the target parameter of interest as well as how it may create bias due to a lack of appropriate control for time-dependent confounders. We also observe evidence that the cross-validated variance acts well as a measure of support in the data, by being minimized at finer discretizations as the sample size increases

Relationship between Adherence Level to Statins, Clinical Issues and Health-Care Costs in Real-Life Clinical Setting

AbstractObjectiveStatins have been shown to reduce the risk of major cardiovascular disease. We recognize that there is a major gap between the use of statins in actual practice and treatment guidelines for dyslipidemia. Low adherence to statins may have a significant impact on clinical issues and health-care costs. The objective is to evaluate the impact of low adherence to statins on clinical issues and direct health-care costs.MethodsA cohort of 55,134 patients newly treated with statins was reconstructed from the Régie de l'Assurance Maladie du Québec and Med-Echo databases. Subjects included were aged between 45 and 85, initially free of cardiovascular disease, newly treated with statins between 1999 and 2002, and followed-up for a minimum of 3 years. Adherence to statins was measured in terms of the proportion of days' supply of medication dispensed over a defined period, and categorized as ≥80% or <80%. The adjusted odds ratio (OR) of cardiovascular events between the two adherence groups was estimated using a polytomous logistic analysis. The mean costs of direct health-care services were evaluated. A two-part model was applied for hospitalization costs.ResultsThe mean high adherence level to statins was around to 96% during follow-up; and this value was at 42% for the low adherence level. The patients with low adherence to statins were more likely to have coronary artery disease (OR 1.07; 95% confidence interval [CI], 1.01–1.13), cerebrovascular disease (OR 1.13; 95% CI 1.03–1.25), and chronic heart failure within 3-year period of follow-up (OR 1.13; 95% CI 1.01–1.26). Low adherence to statins was also associated with an increased risk of hospitalization by 4% (OR 1.04; 95% CI 1.01–1.09). Among patients who were hospitalized, low adherence to statins was significantly associated with increase of hospitalization costs by approximately $1060/patient for a 3-year period.ConclusionLow adherence to statins was correlated with a higher risk of cardiovascular disease, hospitalization rate, and hospitalization costs. An increased level of adherence to statins agents should provide a better health status for individuals and a net economic gain

Bioleaching of Uranium Tailings as Secondary Sources for Rare Earth Elements Production.

Tailings from inactive uranium mine sites represent a potential secondary source of rare earth elements (REEs). For this study, two mine tailings (DT and RAT) from restored uranium sites in Ontario, Canada, were used. Bioleaching experiments were conducted with a mix of native sulfur- and iron-oxidizing bacteria to test the solubilization of REEs, U and Th at different temperatures (20, 30 and 40 °C). The selective recovery of REEs from bioleaching solution was evaluated using different ion exchange resins. The mineralogical characterization revealed that DT tailings were mainly composed of quartz, pyrite, gypsum and silicates, whereas RAT tailings were mainly composed of quartz. The maximum solubilization of heavy and light REEs (HREEs and LREEs, respectively), Th and U reached 54%, 6%, 60% and 51% for RAT after 35 days at pH 2, T = 30 °C and pulp density = 10% (w/v). Higher extraction yields were obtained for DT, with 58% of HREEs, 14% of LREEs, 85% of Th and 89% of U solubilized under the same conditions. The use of Lewatit TP272 resin for the recovery of Sc (94%) and U (99%) followed by the Lewatit SP112 resin for the recovery of Th (57%) and REEs (81% LREEs and 65% HREEs) seemed a promising method for the co-extraction of the key elements from the bioleaching solution

Mass balance study of a multistage process for the purification of a fluorspar by-product from a rare earth element carbonatite deposit.

Fluorspar, also known as fluorite (CaF₂), is commercially important in metallurgical (e.g. used as slag viscosity modifier), ceramic (e.g. used to manufacture glass), and chemical industries (e.g. production of commercial HF). In the present study, a process has been developed to produce a ceramic grade fluorspar by-product from a rare earth element (REE)-bearing carbonatite deposit. The objective of the present study was to conduce a mass balance assessment of a CaF₂ by-product purification process as well as an economic evaluation of the final flotation step to determine the advantage/limitation of this additional step to improve the purity of CaF₂ from metallurgical to ceramic grade. After an initial flotation step to produce feed, the fluorspar purification process consisted of four steps. Firstly, a magnetic separation step was conducted to pre-concentrate the fluorspar into a non-magnetic fraction, while concentrating Fe- and REE-bearing minerals in the magnetic fraction. Secondly, the non-magnetic fraction was subjected to an acid leaching step to solubilize carbonates. Thirdly, the leached solid was treated again by magnetic separation to remove the further liberated REE-bearing minerals from the fluorspar minerals. Finally, a flotation step was performed to depress silicate minerals in the tailings fraction and thus to improve fluorspar grade in the concentrate. The purity of fluorspar increased from 15.6% in the feed (no commercial value, residue to be disposed of) to 95.1% in the final product (ceramic grade). According to the mass balance calculations, approximately 98.6 g of ceramic grade CaF₂ was recovered from 1 kg of feed material and the output/input ratio of fluorspar was estimated at 94.0%. The costs of the flotation process develop to improve the purity of CaF₂ from metallurgical to ceramic grade were estimated at 194 $CAD.t⁻¹, while the revenue to be generated by the ceramic grade fluorspar obtained were estimated at 244$CAD.t⁻¹, indicating that the additional flotation step is economically feasible and beneficial to the company, not only to upgrade fluorspar by-product (from commercial to ceramic grade), but also to generate a profit of at least 50 $CAD.t⁻¹