Pigeot-Kübler, Iris
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Pigeot-Kübler, Iris
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Pigeot-Kübler, Iris
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Item-typ:Veröffentlichung, Controlling for unobserved confounders in observational studies using large health care databases by means of instrumental variables in time-to-event analysisRandomized controlled trials cannot provide all necessary information about drug reactions as they are limited by several factors. Observational studies in free-living populations are therefore necessary. Large health care databases are frequently used for this purpose. A common problem of analyses based on these databases is that confounding variables are often not recorded, so that effects are inconsistently estimated. Under certain conditions instrumental variables can eliminate confounding bias, so that IV estimators can consistently estimate treatment effects. Instrumental variable methods are well established for continuous outcomes using linear regression models, where two-stage least squares are typically used. However, in time-to-event analysis no such common instrumental variable method exists. Even if the proportional hazards model is used, two-stage estimators to account for instrumental variables are only justified for rare events. The aim of this thesis is therefore to explore two-stage instrumental variable estimation for time-to-event outcomes in large health care databases if the assumption of rare events does not hold true.Dissertation709 279 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Statistical modeling of physical activity based on accelerometer data(2016-03-21); ; ; This thesis focuses on the objective measurement of physical activity (PA), recorded by accelerometers. Chapter 2 describes the objective measurement of PA using accelerometers in contrast to subjective measurements like PA questionnaires. Chapter 3 presents the basic assumption on PA. Contrary to the cutpoint method, it is more realistic to assume that human activity behavior consists of a sequence of non-overlapping, distinguishable activities that can be represented by a mean intensity level. The recorded accelerometer counts scatter around this mean level. In Chapter 4, two novel approaches to better capture PA are developed and implemented. The Hidden Markov models are stochastic models that allow fitting a Markov chain with a predefined number of activities to the data. Expectile regression utilizing the Whittaker smoother with an L0-penalty is introduced as a second innovative approach. Expectile regression is compared to HMMs and the cutpoint method in a simulation study. Chapter 5 presents the results of four studies on PA. Chapter 6 summarizes and discusses the findings of the previous chapters and ends with an outlook on future research.Dissertation381 248 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Möglichkeiten und Grenzen der Datenauswertung in epidemiologischen Krebsregistern(2016-04-12); ; ; Population-based (epidemiological) cancer registries are institutions for the collection, storage, processing, analysis and interpretation of data on the incidence, prevalence and mortality of cancers within defined registration areas. Since the fifties cancer registries have provided comparative statistics. Since 2009, all new cases of cancer nationwide are being systematically registered in Germany. However, in interpreting cancer registry data there are several important aspects that should be kept in mind.Dissertation309 156 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Designs and analytical strategies to control for unmeasured confounding in studies based on administrative health care databases(2017-07-21); ; ; Studies based on routine data of statutory health insurances require the adequate consideration of unmeasured confounders. This thesis investigated two methods to cope with this problem: (i) Classic two-phase designs collect additional data for a stratified subset (phase 2) of all patients (phase 1). An extension was proposed that does not need a stratification of the data but a proper model for participation in phase 2. A simulation study comparing the extended method with multiple imputation (MI) as an alternative revealed that MI resulted in less biased and more precise estimators of the treatment effect. (ii) The high-dimensional propensity score (HDPS) algorithm automatically selects hundreds of empirical confounders from the underlying database, but was mainly applied in pharmacoepidemiology. This thesis investigated the HDPS algorithm in a study in health services research, where a shift in the effect estimates towards a more plausible result was achieved. The further development of these or similar methods is needed in the near future, since studies based on linking routine data with other data source are gaining in importance.Dissertation575 146 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Schätzung der Input- und Response-Funktion bei numerischer Konvolution und Dekonvolution im Rahmen pharmakokinetischer UntersuchungenA numerical procedure for convolution and deconvolution of pharmacokinetic data is looked at as a statistical estimation problem. Estimators for the input-and response function based on a point-area convolution method are derived and their asymptotical properties are discussed. Several approaches to estimate the asymptotic variance of the estimators including jackknife and bootstrap techniques are discussed. A simulation study to investigate the finite sample performance of the estimators is presented.Dissertation243 193 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Zeitreihenzerlegung mittels des mehrkomponentigen Verallgemeinerten Berliner Verfahrens(2008-06-17); ; The subject of this thesis is the multi-component Generalized Berlin Method (mehrkomponentiges Verallgemeinertes Berliner Verfahren, VBV), a method oftime series analysis, with approximates a given time series through the approximation of its influence components based on differential splines.After a detailed introduction to VBV, including, in particular, differential splines, its efficiency as well as some of its applications will be discussed.Moreover, the investigation of the smoothing parameters is carried out by means of (generalized) cross-validation. Last but not least, the best linear unbiased prediction (BLUP) in case of VBV is analyzed.Dissertation300 208 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Automatisierte Verfahren in der Arzneimittelsicherheitsforschung(2012-12-14); ; ; The evaluation of routinely collected data, such as claims data of statutory health insurances, has been pursued in drug safety research in the recent years as these data generally contain more information than spontaneous reporting registers. In this thesis it is examined how the analysis of claims data using automated signal detection methods can lead to reliable conclusions about the risk profile of drugs. The idea of disproportionality analysis is described. The theoretical background of the Gamma- Poisson Shrinkers and its extension for the analysis of longitudinal data is given as well as results of a practical application. To address the problem of the often missing consideration of confounders in signal detection, the propensity score and the High-dimensional propensity score (HDPS) are discussed and compared in an application study. Finally, the ideas of disproportionality analysis and automated covariate selection via HDPS are theoretically combined and practically applied to claims data. In conclusion, all investigated automated methods can be applied successfully to claims data, even if the latter approach is still in need of further adjustments.Dissertation515 156