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1.
OBJECTIVE: Weight- and shape-related self-evaluation refers to the process whereby an individual determines her self-worth based on an evaluation of her body weight and shape. This is a hallmark feature of both anorexia and bulimia nervosa, as specified in the 4th ed. of the Diagnostic and Statistical Manual of Mental Disorders. The purpose of this study was to further our understanding of weight-related self-evaluation in eating-disordered women. METHOD: Eating-disordered patients, restrained eaters, and unrestrained eaters completed an experimenter-designed questionnaire that examines different dimensions of weight-related self-evaluation (i.e., the Multidimensional Weight-Related Self-Evaluation Inventory). RESULTS: Results revealed that weight-related self-evaluation is a feature shared, to some extent, by both eating-disordered patients and restrained eaters. However, eating-disordered patients extend weight-related self-evaluation to include more domains of self-esteem than did restrained eaters. DISCUSSION: These findings support a multidimensional approach to weight-related self-evaluation and further our understanding of the process of weight-related self-evaluation in eating-disordered patients.  相似文献   

2.
Estimation of treatment effects with causal interpretation from observational data is complicated because exposure to treatment may be confounded with subject characteristics. The propensity score, the probability of treatment exposure conditional on covariates, is the basis for two approaches to adjusting for confounding: methods based on stratification of observations by quantiles of estimated propensity scores and methods based on weighting observations by the inverse of estimated propensity scores. We review popular versions of these approaches and related methods offering improved precision, describe theoretical properties and highlight their implications for practice, and present extensive comparisons of performance that provide guidance for practical use.  相似文献   

3.
Madden D  Nolan A  Nolan B 《Health economics》2005,14(10):1047-1060
In Ireland, approximately 30% of the population receive free GP services (medical card patients) while the remainder (private patients) must pay for each visit. In 1989, the manner in which GPs were reimbursed by the State for their medical card patients was changed from fee-for-service to capitation while private patients continued to pay on a fee-for-service basis. Concerns about supplier-induced demand were in part responsible for this policy change. The purpose of this paper is to examine the extent to which the utilisation of GP services is influenced by the reimbursement system facing GPs, by comparing visiting rates for the two groups before and after this change. Using a difference-in-differences approach on pooled micro-data from 1987, 1995 and 2000, we find that medical card eligibility has a consistently positive and significant effect on the utilisation of GP services. However, the differential in visiting rates between medical card patients and others did not narrow between 1987 and 1995 or 2000, as might have been anticipated if supplier-induced demand played a major role prior to the change in reimbursement system.  相似文献   

4.
Smith RD 《Health economics》2001,10(6):487-497
This paper directly compares the relative sensitivity of time-trade-off (TTO) and willingness-to-pay (WTP) values obtained for various levels of change in health status. This was achieved by administering a TTO and WTP survey to a population of 50 subjects, assessing their valuation of various degrees of change in health status. It was found that, overall, WTP is more sensitive than TTO in distinguishing between different dimensions of health at the same nominal level of health status (only four WTP values not significantly different, compared with eight TTO values). In addition, WTP was also more sensitive to differences in quality of life between different levels of health within each dimension (all values significantly different from each other, with TTO yielding three insignificant relationships). These results tentatively suggest, therefore, that WTP seems to be a more sensitive measure of change in health status than TTO.  相似文献   

5.
This paper examines the identification problem in age‐period‐cohort models that use either linear or categorically coded ages, periods, and cohorts or combinations of these parameterizations. These models are not identified using the traditional fixed effect regression model approach because of a linear dependency between the ages, periods, and cohorts. However, these models can be identified if the researcher introduces a single just identifying constraint on the model coefficients. The problem with such constraints is that the results can differ substantially depending on the constraint chosen. Somewhat surprisingly, age‐period‐cohort models that specify one or more of ages and/or periods and/or cohorts as random effects are identified. This is the case without introducing an additional constraint. I label this identification as statistical model identification and show how statistical model identification comes about in mixed models and why which effects are treated as fixed and which are treated as random can substantially change the estimates of the age, period, and cohort effects. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

6.
BACKGROUND: Coke-oven workers (COWs) are occupationally exposed to high concentrations of polycyclic aromatic hydrocarbons (PAHs). Urinary 8-hydroxy-2-deoxyguanosine (8-OH-dG) and 1-hydroxypyrene (1-OHP) are biological markers of oxidative DNA damage and PAHs metabolism, respectively. In this study, we investigated whether polymorphisms of glutathione S-transferase (GSTM1 and GSTT1) can modulate the relationship between urinary 8-OH-dG and 1-OHP concentrations among the COWs. METHODS: This was a cross-sectional study. Between February and November of 2001, 53 topside-oven and 130 side-oven workers with the presence of GSTM1 and GSTT1 genotypes were investigated. RESULTS: Urinary 1-OHP and 8-OH-dG concentrations (mean +/- SD) in the topside-oven workers with the presence of GSTM1 were 107.2 +/- 107.9 and 15.3 +/- 9.7 ng/ml, respectively, which were not significantly different from those in the absence of GSTM1 (84.1 +/- 104.5 and 12.8 +/- 14.1 ng/ml). The similar insignificant results were also noted in the sideoven workers. For GSTT1 polymorphism, the results remained insignificant. In contrast, individual excretion of urinary 8-OH-dG and 1-OHP concentrations were still highly correlated (Spearman correlation coefficients: r = 0.43, P < 0.0001, n = 183). CONCLUSIONS: GST may not play a role in the regulation of metabolism of urinary biological markers in COWs.  相似文献   

7.
While the intent-to-treat (ITT) analysis is widely accepted for superiority trials, there remains debate about its role in non-inferiority trials. It is often said that the ITT tends to be anti-conservative in the demonstration of non-inferiority. This concern has led to some reliance on per-protocol (PP) analyses that exclude patients on the basis of post-baseline events, despite the inherent bias of such analyses. We compare ITT and PP results from antibiotic trials presented to the public at the FDA's Anti-infective Drug Advisory Committee from 1999 to 2003. While the number of available trials is too small to produce clear conclusions, these data did not support the assumption that the ITT would lead to smaller treatment difference than the PP, in the setting of antibiotic trials. Possible explanations are discussed.  相似文献   

8.
Hugues Aschard  Vilmundur Gudnason  Tamara B. Harris  Albert V. Smith  Eric Boerwinkle  Michael R. Brown  Alanna C. Morrison  Myriam Fornage  Li‐An Lin  Melissa Richard  Traci M. Bartz  Bruce M. Psaty  Caroline Hayward  Ozren Polasek  Jonathan Marten  Igor Rudan  Mary F. Feitosa  Aldi T. Kraja  Michael A. Province  Xuan Deng  Virginia A. Fisher  Yanhua Zhou  Lawrence F. Bielak  Jennifer Smith  Jennifer E. Huffman  Sandosh Padmanabhan  Blair H. Smith  Jingzhong Ding  Yongmei Liu  Kurt Lohman  Claude Bouchard  Tuomo Rankinen  Treva K. Rice  Donna Arnett  Karen Schwander  Xiuqing Guo  Walter Palmas  Jerome I. Rotter  Tamuno Alfred  Erwin P. Bottinger  Ruth J. F. Loos  Najaf Amin  Oscar H. Franco  Cornelia M. van Duijn  Dina Vojinovic  Daniel I. Chasman  Paul M. Ridker  Lynda M. Rose  L. Adrienne Cupples 《Genetic epidemiology》2016,40(5):404-415
Studying gene‐environment (G × E) interactions is important, as they extend our knowledge of the genetic architecture of complex traits and may help to identify novel variants not detected via analysis of main effects alone. The main statistical framework for studying G × E interactions uses a single regression model that includes both the genetic main and G × E interaction effects (the “joint” framework). The alternative “stratified” framework combines results from genetic main‐effect analyses carried out separately within the exposed and unexposed groups. Although there have been several investigations using theory and simulation, an empirical comparison of the two frameworks is lacking. Here, we compare the two frameworks using results from genome‐wide association studies of systolic blood pressure for 3.2 million low frequency and 6.5 million common variants across 20 cohorts of European ancestry, comprising 79,731 individuals. Our cohorts have sample sizes ranging from 456 to 22,983 and include both family‐based and population‐based samples. In cohort‐specific analyses, the two frameworks provided similar inference for population‐based cohorts. The agreement was reduced for family‐based cohorts. In meta‐analyses, agreement between the two frameworks was less than that observed in cohort‐specific analyses, despite the increased sample size. In meta‐analyses, agreement depended on (1) the minor allele frequency, (2) inclusion of family‐based cohorts in meta‐analysis, and (3) filtering scheme. The stratified framework appears to approximate the joint framework well only for common variants in population‐based cohorts. We conclude that the joint framework is the preferred approach and should be used to control false positives when dealing with low‐frequency variants and/or family‐based cohorts.  相似文献   

9.
Time-to-event regression is a frequent tool in biomedical research. In clinical trials this time is usually measured from the beginning of the study. The same approach is often adopted in the analysis of longitudinal observational studies. However, in recent years there has appeared literature making a case for the use of the date of birth as a starting point, and thus utilize age as the time-to-event. In this paper, we explore different types of age-scale models and compare them with time-on-study models in terms of the estimated regression coefficients they produce. We consider six proportional hazards regression models that differ in the choice of time scale and in the method of adjusting for the years before the study. By considering the estimating equations of these models as well as numerical simulations we conclude that correct adjustment for the age at entry is crucial in reducing bias of the estimated coefficients. The unadjusted age-scale model is inferior to any of the five other models considered, regardless of their choice of time scale. Additionally, if adjustment for age at entry is made, our analyses show very little to suggest that there exists any practically meaningful difference in the estimated regression coefficients depending on the choice of time scale. These findings are supported by four practical examples from the Framingham Heart Study.  相似文献   

10.
Infant mortality and child nutrition in Bangladesh   总被引:1,自引:0,他引:1  
The excess female infant mortality observed in South Asia has typically been attributed to gender discrimination in the intra-household allocation of food and medical care. However, studies on child nutrition find no evidence of gender differences. A natural explanation could be that in environments of high infant mortality of females, the surviving children are healthier, so that child nutrition cannot be studied independently of mortality. In this paper, we use data from the 2004 Bangladesh Demographic Health Survey to investigate if there are any gender differences in survival probabilities and whether this leads to differences in child nutrition. We argue the importance of establishing whether or not there exists a dependence relationship between the two random variables--infant mortality and child nutrition--and in order to detect this we employ a copula approach to model specification. The results suggest, for example, that while male children have a significantly lower likelihood of surviving their first year relative to female children, should they survive they have significantly better height-for-age Z-scores. From a policy perspective, household wealth and public health interventions such as vaccinations are found to be important predictors of better nutritional outcomes.  相似文献   

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