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Despite the growing popularity of propensity score (PS) methods in epidemiology, relatively little has been written in the epidemiologic literature about the problem of variable selection for PS models. The authors present the results of two simulation studies designed to help epidemiologists gain insight into the variable selection problem in a PS(More)
Early diagnosis is a tenet in oncology and should enable early treatment with the expectation of improved outcome. Extent and determinants of patient delay of diagnosis in breast cancer patients and its impact on stage of disease were examined in a population based study among female breast cancer patients in Germany. Two hundred and eighty-seven women,(More)
OBJECTIVES To analyse differences of opinions on indications for primary total hip replacements (THRs) within and between groups of orthopaedic surgeons and the physicians who refer patients to them. METHODS 22 orthopaedic centres in 12 European countries took part, resulting in a postal survey of 304 orthopaedic surgeons and 314 referring physicians.(More)
CONTEXT There has been rapid adoption of newer radiation treatments such as intensity-modulated radiation therapy (IMRT) and proton therapy despite greater cost and limited demonstrated benefit compared with previous technologies. OBJECTIVE To determine the comparative morbidity and disease control of IMRT, proton therapy, and conformal radiation therapy(More)
Doubly robust estimation combines a form of outcome regression with a model for the exposure (i.e., the propensity score) to estimate the causal effect of an exposure on an outcome. When used individually to estimate a causal effect, both outcome regression and propensity score methods are unbiased only if the statistical model is correctly specified. The(More)
Often, data on important confounders are not available in cohort studies. Sensitivity analyses based on the relation of single, but not multiple, unmeasured confounders with an exposure of interest in a separate validation study have been proposed. In this paper, the authors controlled for measured confounding in the main cohort using propensity scores(More)
BACKGROUND Although the influenza vaccine is recommended for patients with end-stage renal disease, little is known about its effectiveness. Observational studies of vaccine effectiveness (VE) are challenging because vaccinated subjects may be healthier than unvaccinated subjects. METHODS Using US Renal Data System data, we estimated VE for influenza-like(More)
BACKGROUND In contrast to most observational studies, the randomized Physicians' Health Study found no association between aspirin use and colorectal cancer after 5 years. OBJECTIVE To determine the effect of randomly assigned aspirin treatment and self-selected aspirin use on the incidence of colorectal cancer after 12 years and to identify factors(More)
BACKGROUND Obesity and diabetes are established risk factors for colorectal cancer but have mainly been assessed independently. There are few data about whether the metabolic syndrome, which refers to a clustering of cardiovascular disease risk factors thought to be related to insulin resistance, including obesity, type 2 diabetes, hyperlipidemia, and(More)
The aim of our study was to identify any differences in the quality of life (QOL) of breast cancer survivors one year after diagnosis when the acute treatment effects should not longer be apparent. QOL was assessed in a population-based cohort of 387 women with breast cancer from Saarland (Germany) using the European Organisation for Research and Treatment(More)