Partial logistic relevance vector machines in survival analysis

The use of relevance vector machines to flexibly model hazard rate functions is explored. This technique is adapted to survival analysis problems through the partial logistic approach. The method exploits the Bayesian automatic relevance determination procedure to obtain sparse solutions and it incorporates the flexibility of kernel-based models. Example results are presented on literature data from a head-and-neck cancer survival study using Gaussian and spline kernels. Sensitivity analysis is conducted to assess the influence of hyperprior distribution parameters. The proposed method is then contrasted with other flexible hazard regression methods, in particular the HARE model proposed by Kooperberg et al. [16]. A simulation study is conducted to carry out the comparison. The model developed in this paper exhibited good performance in the prediction of hazard rate. The application of this sparse Bayesian technique to a real cancer data set demonstrated that the proposed method can potentially reveal characteristics of the hazards, associated with the dynamics of the studied diseases, which may be missed by existing modeling approaches based on different perspectives on the bias vs. variance balance.     

Maximum likelihood estimation of correlation between maximal oxygen consumption and the 6-min walk test in patients with chronic heart failure

Maximal oxygen consumption (VO₂max) is the standard measurement used to quantify cardiovascular functional capacity and aerobic fitness. Unfortunately, it is a costly, impractical and labour-intensive measure to obtain. The 6-min walk test (6MWT) also assesses cardiopulmonary function, but in contrast to the VO₂max test, it is inexpensive and can be performed almost anywhere. Various medical studies have addressed the correlation between VO₂max and 6MWT in patients with chronic heart failure. Of particular interest, from a medical point of view, is the conditional correlation between the two measures given the individual's height, weight, age and gender. In this paper, we have calculated the maximum likelihood estimate of the conditional correlation in patients with chronic heart failure under the assumption of skew normality. Data were recorded from 98 patients in the Operative Unit of Thoracic Surgery in Bari, Italy. The estimated conditional correlation was found to be much smaller than estimated marginal correlations reported in the medical literature.     

Local stationarity in small area estimation models

Small area estimators are often based on linear mixed models under the assumption that relationships among variables are stationary across the area of interest (Fay–Herriot models). This hypothesis is patently violated when the population is divided into heterogeneous latent subgroups. In this paper we propose a local Fay–Herriot model assisted by a Simulated Annealing algorithm to identify the latent subgroups of small areas. The value minimized through the Simulated Annealing algorithm is the sum of the estimated mean squared error (MSE) of the small area estimates. The technique is employed for small area estimates of erosion on agricultural land within the Rathbun Lake Watershed (IA, USA). The results are promising and show that introducing local stationarity in a small area model may lead to useful improvements in the performance of the estimators.     

Family Trajectories and Health: A Life Course Perspective

This paper investigates the role of family trajectory, i.e., the whole sequence of family events during the life course of early adults in shaping their health outcomes. Union formation and childbearing are jointly considered, since the two life domains are highly connected and their intersections may have an effect on health outcomes. Data come from wave I and wave IV of the National Longitudinal Study of Adolescent Health (Add Health) in the United States. The paper is divided in two parts. The first part focuses on family transitions and investigates if changes in timing (when events happen), quantum (what and how many transitions), and ordering (in what order), have an effect on the health of young women. In the second part, life course trajectories are classified into six groups representing different ideal-types of family trajectories and the association of these trajectories with health outcomes is explored. Results suggest that family trajectories play an important role on different health outcomes. Controlling for selection and background characteristics, precocious and “non-normative” transitions are associated with lower self-reported health and higher propensity of smoking and drinking.     

Commissioned analysis of surgical performance using routine data: lessons from the Bristol inquiry

The public inquiry into paediatric cardiac surgery at the Bristol Royal Infirmary commissioned the authors to design and conduct analyses of routine data sources to compare surgical outcomes between centres. Such analyses are necessarily complex in this context but were further hampered by the inherent inconsistencies and mediocre quality of the various sources of data. Three levels of analysis of increasing sophistication were carried out. The reasonable consistency of the results arising from different sources of data, together with a number of sensitivity analyses, led us to conclude that there had been excess mortality in Bristol in open heart operations on children under 1 year of age. We consider criticisms of our analysis and discuss the role of statisticians in this inquiry and their contribution to the final report of the inquiry. The potential statistical role in future programmes for monitoring clinical performance is highlighted.     

Rights of Foreign Workers and the Politics of Migration in South-East and East Asia

The issue of cross‐border migration in South‐East and East Asia is linked to the integration of regional, if not global, labour markets. The types of labour that are currently in demand have changed substantially since the 1990s in terms of (1) overall magnitude, (2) gender composition, and (3) increased diversification. This paper, however, focuses upon those workers classified as unskilled as they constitute numerically the largest and most vulnerable group. The challenges to provide adequate protection from, and prevention of, exploitative and abusive practices that seriously minimize the socio‐economic benefits for these workers are linked to migration policies and the issue of rights in the origin and destination countries. This paper's objective is to provide a broad outline of the emerging trends and issues revolving around contemporary cross‐border labour migration and the politics of migrants' rights in South‐East and East Asia, illustrated by the difficulties experienced with the ratification of the 1990 United Nations Convention on the Rights of All Migrants and their Families (ICMR). The data this paper is based upon were collected for a report commissioned by the United Nations Educational, Scientific and Cultural Organization (UNESCO) with fieldwork carried out in seven countries located in the Asia Pacific region. It is argued that ratification of the ICMR is obstructed by politics and by a lack of political will. A rights‐based approach to the protection of migrant labour is thus related to a number of macro and micro level issues, revolving around development and practices of “good governance” in addition to interstate relations. This means that the promotion of migrants' rights requires a holistic approach addressing national and transnational issues in an era of increasing mobility across borders.     

Modelling Job-Search Duration from the Italian Labour Force Data

ABSTRACT: Micro (and possibly panel) data from the Labour Force Surveys are a valuable source for analysing the labour supply behaviour. Among the information collected by the quarterly Italian Labour Force Survey conducted by ISTAT (the Italian national statistical agency), there are data on the duration of job-search. From a single survey, one can only know the duration of search up to the time of the interview. Nonetheless, by appropriately exploiting the longitudinal structure of the survey (the sample scheme is a rotated one, with a 50|X% overlapping of the sample units in two subsequent quarters) it is possible to measure, although imperfectly, some completed spells of job-search. In this paper, we try to model the duration of job-search for a sample of young unemployed. Considerable attention is devoted to the measure of duration of search, and to the evaluation of its accuracy. A one state proportional hazard model is specified and estimated, accounting also for unobserved heterogeneity. The model is estimated on a sample of young (15 to 29 years old) unemployed in January 1986 reinterviewed in April, in an Italian region (Lombardy). The major finding is a fairly clear evidence, both for males and females, of negative duration dependence, even after accounting for the unobserved heterogeneity that turns out to affect the female population.     

Always doing your best? Effort and performance in dynamic settings

Theory and Decision - Achieving an ambitious goal frequently requires succeeding in a sequence of intermediate tasks, some being critical for the final outcome, and others not. However, individuals...     

A unique collaboration of female medical providers within the United States Armed Forces: rehabilitation of a marine with post-concussive vestibulopathy

Uncle Sam's loyal nieces have come a long way from the days of World War I. The development of occupational and physical therapy was heavily influenced by an early relationship with medical specialists during the First World War. This relationship can be considered largely responsible for the eventual acceptance (by the Armed Forces) of women working in this area. Over the past decade active duty women have seen many changes in opportunities to serve and are now stationed aboard aircraft carriers, performing roles previously considered for male personnel. We report a case study of the medical care provided by both military and civilian women working for the United States Armed Forces. Initial assessment was conducted in a battalion aid station of a United States Marine Corp base and the subject was then referred to a military medical center with highly technical vestibular assessment and rehabilitation services. The subject's case represents a unique collaboration of women therapists, enabling a Marines' access to timely and accurate assessment, treatment and ultimately, successful return to active duty. This case study is one of many examples of the acceptance and successful integration of women as providers of medical care within the Military's medical framework.