This thesis develops and investigates statistical methods for two frailty models in the analysis of time-to-event data.The first part of the thesis deals with the statistical assessment of the... Show moreThis thesis develops and investigates statistical methods for two frailty models in the analysis of time-to-event data.The first part of the thesis deals with the statistical assessment of the slowing down of human death rates at advanced ages. Such mortality deceleration can be described through the gamma-Gompertz model as an effect of selection in heterogeneous populations. As the frailty variance of this proportional hazards frailty model may lie on the boundary of the parameter space, statistical techniques have to be adjusted to this non-standard condition. Chapter 2 presents the asymptotic properties of likelihood inference in this model. In Chapter 3, aspects of study design are discussed, such as the information loss if samples are restricted to cover only survivors beyond some high age. Chapter 4 introduces focused model selection as a new approach to assessing mortality deceleration.The second part of the thesis is concerned with inference in a joint frailty model for recurrent events and a terminal event in two different observational settings. Chapter 5 considers the situation of intermittent observation of the recurrence process, such that only interval counts of recurrent events are available. Chapter 6 examines the situation of delayed entry, in which individuals can only be included in the recurrent event study if they have not yet experienced the terminal event. Show less
This thesis addresses current treatment strategies in older cancer patients, as well as the consequences of these decisions for clinical outcomes. In addition, this thesis investigated the value of... Show moreThis thesis addresses current treatment strategies in older cancer patients, as well as the consequences of these decisions for clinical outcomes. In addition, this thesis investigated the value of frailty assessment in different cancer populations and described the implementation of a multidisciplinary team approach in frail older cancer patients. Show less
Older emergency department (ED) patients are at high risk of adverse health outcomes, such as mortality or functional decline. Early identification of those patients who are at highest risk gives... Show moreOlder emergency department (ED) patients are at high risk of adverse health outcomes, such as mortality or functional decline. Early identification of those patients who are at highest risk gives an opportunity to target interventions and guide treatment decisions for those who need it most.This thesis describes the clinical value of using geriatric screening in the ED. Geriatric screening identifies older patients at high risk of both short- and long-term poor outcomes and provides valuable information for care providers treating acutely hospitalized older patients. The results from screening could aid in individualized treatment decisions to acquire more personalized care, and therefore gives an opportunity to optimize outcomes for older patients.Implementation of screening programs in the fast-paced environment of everyday ED practice remains scarce. The results of this thesis show that the implementation of a geriatric screening program in routine ED practice is feasible and the use of screening is accepted by both the users (triage nurses) and the older patients.Using geriatric screening in routine care is therefore useful and feasible. More research will be needed to investigate implementation in different hospitals to generate guidance on how geriatric screening tools can be successfully implemented on a wide scale. Show less
