Nested exposure case-control sampling: a sampling scheme to analyze rare time-dependent exposures

For large cohort studies with rare outcomes, the nested case-control design only requires data collection of small subsets of the individuals at risk. These are typically randomly sampled at the observed event times and a weighted, stratified analysis takes over the role of the full cohort analysis. Motivated by observational studies on the impact of hospital-acquired infection on hospital stay outcome, we are interested in situations, where not necessarily the outcome is rare, but time-dependent exposure such as the occurrence of an adverse event or disease progression is. Using the counting process formulation of general nested case-control designs, we propose three sampling schemes where not all commonly observed outcomes need to be included in the analysis. Rather, inclusion probabilities may be time-dependent and may even depend on the past sampling and exposure history. A bootstrap analysis of a full cohort data set from hospital epidemiology allows us to investigate the practical utility of the proposed sampling schemes in comparison to a full cohort analysis and a too simple application of the nested case-control design, if the outcome is not rare.

     

Writing Distinction – Eine illegitime Kultur als subkulturelles Feld

Graffiti is an illegitimate culture, yet with high potential for distinction and abstract aesthetic principles. The article considers these characteristics as result of the process of the autonomization of graffiti as subcultural field and aims to reconstruct its field logic.     

Gender differences in predictors of late-life health insurance knowledge

For many older adults having access to affordable health care is a major concern. The present study's goal was to examine what factors were related to individuals' knowledge of late-life health insurance. A total of 131 women and 116 men (all aged 55-71) answered questions about private, Medicare, Medigap, and long-term care insurances. In addition, they answered demographic, personality, and health status questions. Results revealed that different factors are related to men's and women's knowledge of late-life health insurance options implying genderspecific educational interventions would be more effective than current educational interventions.     

The time‐dependent “cure‐death” model investigating two equally important endpoints simultaneously in trials treating high‐risk patients with resistant pathogens

A variety of primary endpoints are used in clinical trials treating patients with severe infectious diseases, and existing guidelines do not provide a consistent recommendation. We propose to study simultaneously two primary endpoints, cure and death, in a comprehensive multistate cure‐death model as starting point for a treatment comparison. This technique enables us to study the temporal dynamic of the patient‐relevant probability to be cured and alive. We describe and compare traditional and innovative methods suitable for a treatment comparison based on this model. Traditional analyses using risk differences focus on one prespecified timepoint only. A restricted logrank‐based test of treatment effect is sensitive to ordered categories of responses and integrates information on duration of response. The pseudo‐value regression provides a direct regression model for examination of treatment effect via difference in transition probabilities. Applied to a topical real data example and simulation scenarios, we demonstrate advantages and limitations and provide an insight into how these methods can handle different kinds of treatment imbalances. The cure‐death model provides a suitable framework to gain a better understanding of how a new treatment influences the time‐dynamic cure and death process. This might help the future planning of randomised clinical trials, sample size calculations, and data analyses.     

On pseudo-values for regression analysis in competing risks models

For regression on state and transition probabilities in multi-state models Andersen et al. (Biometrika 90:15–27, 2003) propose a technique based on jackknife pseudo-values. In this article we analyze the pseudo-values suggested for competing risks models and prove some conjectures regarding their asymptotics (Klein and Andersen, Biometrics 61:223–229, 2005). The key is a second order von Mises expansion of the Aalen-Johansen estimator which yields an appropriate representation of the pseudo-values. The method is illustrated with data from a clinical study on total joint replacement. In the application we consider for comparison the estimates obtained with the Fine and Gray approach (J Am Stat Assoc 94:496–509, 1999) and also time-dependent solutions of pseudo-value regression equations.     

Wann werden Ehen getrennt?

With regard to marriages, numerous studies have reported a time-dependent course of the dissolution rate, which is characterized by an initial rise and a subsequent decline after a couple of years. The article at hand discusses potential explanations for the correlation of marital duration and the risk of dissolution and examines them on the basis of the Family Survey 2000. The results indicate, among other things, that the concentration of childbirths in an early stage of marriage leads to a slow-down of the initial rise of the dissolution rate whereas it weakens its later decline as the stabilizing effect of shared children on marriage decreases when the children become older. There are significant differences with respect to the dependency of the dissolution risk on marital duration between the successive marriage cohorts, depending on the wife’s occupation, age at marriage as well as between couples who did vs. those who did not cohabitate before marriage. The results suggest that relationship-specific processes as well as changes of the marital preconditions resulting from the partners’ respective ages contribute to the explanation of the course of the dissolution rate.     

Shift scheduling for tank trucks

In this paper we deal with shift scheduling of tank trucks for a small oil company. Given are a set of tank trucks with different characteristics and a set of drivers with different skills. The objective is to assign a feasible driver to every shift of the tank trucks such that legal and safety restrictions are satisfied, the total working times of the drivers are within desired intervals, requested vacation of the drivers is respected and the trucks are assigned to more favored drivers. We propose a two-phase solution algorithm which is based on a mixed integer linear programming formulation and an improvement procedure. Computational results are reported showing that the algorithm is able to generate feasible schedules in a small amount of time.