Understanding Mortality of Femoral Fractures Following Low-Impact Trauma in Persons With and Without Care Need

Modeling unmeasured baseline information in observational time-to-event data subject to delayed study entry

Unmeasured baseline information in left-truncated data situations frequently occurs in observational time-to-event analyses. For instance, a typical timescale in trials of antidiabetic treatment is "time since treatment initiation", but individuals may have initiated treatment before the start of longitudinal data collection. When the focus is on baseline effects, one widespread approach is to fit a Cox proportional hazards model incorporating the measurements at delayed study entry. This has been criticized because of the potential time dependency of covariates. We tackle this problem by using a Bayesian joint model that combines a mixed-effects model for the longitudinal trajectory with a proportional hazards model for the event of interest incorporating the baseline covariate, possibly unmeasured in the presence of left truncation. The novelty is that our procedure is not used to account for non-continuously monitored longitudinal covariates in right-censored time-to-event studies, but to utilize these trajectories to make inferences about missing baseline measurements in left-truncated data. Simulating times-to-event depending on baseline covariates we also compared our proposal to a simpler two-stage approach which performed favorably. Our approach is illustrated by investigating the impact of baseline blood glucose levels on antidiabetic treatment failure using data from a German diabetes register.

Dynamic inference in general nested case-control designs

Nested case-control designs are attractive in studies with a time-to-event endpoint if the outcome is rare or if interest lies in evaluating expensive covariates. The appeal is that these designs restrict to small subsets of all patients at risk just prior to the observed event times. Only these small subsets need to be evaluated. Typically, the controls are selected at random and methods for time-simultaneous inference have been proposed in the literature. However, the martingale structure behind nested case-control designs allows for more powerful and flexible non-standard sampling designs. We exploit that structure to find simultaneous confidence bands based on wild bootstrap resampling procedures within this general class of designs. We show in a simulation study that the intended coverage probability is obtained for confidence bands for cumulative baseline hazard functions. We apply our methods to observational data about hospital-acquired infections.

Epidemiology of hip fractures : Systematic literature review of German data and an overview of the international literature

BACKGROUND

Hip fractures are regarded as a worldwide epidemic and a major public health concern. Changing risk factors, local differences and temporal trends contribute to the particular epidemiology of hip fractures. This overview gives a comprehensive insight into the epidemiology of hip fractures and reviews where German data have contributed to the literature.

METHODS

The review of the epidemiology of hip fractures in Germany is based on a systematic literature search in PubMed. Information about the global epidemiology of hip fractures was provided by a selective literature review focusing on specific aspects of the epidemiology of hip fractures.

RESULTS

Hip fracture rates vary more than 100-fold between different countries. In most high-income countries, a rise in age-standardized hip fracture rates was observed until the 1980s and 1990s and a decrease thereafter. Such a decrease has not been observed for Germany so far. Many factors, diseases and drugs have been found to be associated with hip fractures and there is some evidence that fracture risk in later life is already programmed during fetal life and early childhood. Of the hip fracture burden 50% occur in people with disability and in need of care. In nursing homes approximately 4 fractures can be expected in 100 women per year. In people with intellectual or developmental disabilities comparable risks of hip fracture occur 10-40 years earlier than in the general population. Incidence of disability, institutionalization and death are frequent consequences of hip fractures.

CONCLUSION

The epidemiology of hip fractures is characterized by a high burden of disease, local differences, temporal trends, well-defined high-risk populations and many established risk factors.

The wild bootstrap for multivariate Nelson-Aalen estimators

We rigorously extend the widely used wild bootstrap resampling technique to the multivariate Nelson-Aalen estimator under Aalen's multiplicative intensity model. Aalen's model covers general Markovian multistate models including competing risks subject to independent left-truncation and right-censoring. This leads to various statistical applications such as asymptotically valid confidence bands or tests for equivalence and proportional hazards. This is exemplified in a data analysis examining the impact of ventilation on the duration of intensive care unit stay. The finite sample properties of the new procedures are investigated in a simulation study.

Patient Characteristics as Indicator for Care Dependence after Hip Fracture: A Retrospective Cohort Study Using Health Insurance Claims Data From Germany

OBJECTIVES

Hip fractures are common consequences of falls in older adults and, among other negative health outcomes, often lead to care dependence in the long term. Until 2016, the German long-term care insurance classified care recipients according to a standardized classification system consisting of 3 care levels. It was based on required assistance in performing activities of daily living and assessed by a qualified physician or nurse. Thus, care level reflects the degree of care dependence. The aim of this study was to determine relevant patient characteristics, which are related to the likelihood of increasing care dependence in terms of worsening care level after hip fracture.

DESIGN

Retrospective cohort study.

SETTING AND PARTICIPANTS

Statutory health insurance claims data including 122,922 insured individuals living in Germany and aged 65 years or older, who sustained a hip fracture from 2009 through 2011.

MEASURES

The association of patient characteristics with worsening care level in the quarterly period after hip fracture was investigated by means of multinomial logit regression analysis. Death constitutes a competing risk and was modeled as additional nominal outcome.

RESULTS

Among all patients, crude rates were 30.9% for worsening care level, 54.8% for unchanged care level, and 14.4% for death after hip fracture. The multivariate analysis revealed that patient factors male sex, increasing age, increasing comorbidity, increasing inpatient length of stay, and a lack of inpatient rehabilitation were significantly associated with a worsening care level.

CONCLUSIONS/IMPLICATIONS

This study uses the German standardized measurement of care dependence in terms of worsening care level after hip fracture and finds various related patient characteristics. Knowledge of these characteristics helps to identify possible risk groups for care dependence after hip fracture, for which special attention can be provided regarding treatment and prevention of hip fractures.