Joint Modeling of Survival and Longitudinal Ordered Data Using a Semiparametric Approach

Medical research frequently focuses on the relationship between quality of life (QoL) and survival time of subjects. QoL may be one of the most important factors that could be used to predict survival, making it worth identifying factors that jointly affect survival and QoL. We propose a semiparametric joint model that consists of item response and survival components, where these two components are linked through latent variables. Several popular ordinal models are considered and compared in the item response component, while the Cox proportional hazards model is used in the survival component. We estimate the baseline hazard function and model parameters simultaneously, through a profile likelihood approach. We illustrate the method using an example from a clinical study.     

How Do Migrants Fare in a Post‐Apartheid South African Labor Market?1

South African policies have historically emphasized employment as the reason for immigration. In post‐apartheid South Africa, stories about how “immigrants take away our jobs” abound in the mass media, yet few empirical studies have been undertaken to examine the validity of this claim. This study looks at the relationship between migration status, nativity and labor force outcomes in the post‐apartheid labor market. Our results suggest that migrants are more likely to participate in the labor force and to be gainfully employed than the indigenous population. Foreign migrants enjoy the highest labor force participation rates and employment rates in South Africa. South African‐born internal migrants also have significantly higher labor force outcomes than do nonmigrants.     

Modeling Acute Rheumatic Fever

Acute rheumatic fever (ARF) is a major cause of heart disease, rare in developed countries, but of concern in New Zealand, where a unique feature is the prevalence of ARF among Maori and Pacific Island peoples. The incidence and prevalence of ARF in a population are modeled for the New Zealand case, where risks of contracting Group A Streptococcus or developing ARF are allowed to vary according to ethnicity, age, and ARF history. The critical parameter R₀ determines whether a disease will become epidemic or not. A proportional treatment protocol is the most effective at reducing ARF.     

“You Don't Get to Sing a Song When You Have Nothing to Say”: Oliver Mtukudzi's Music as a Vehicle for Socio-Political Commentary

Abstract

Oliver Mtukudzi's music is known for both its musicality and because it addresses social and political issues. Mtukudzi uses his music to tackle the political realities of Zimbabwe and issues related to AIDS, gender and street children. The use of riddles and innuendo is common within Shona music and it is these tools that Mtukudzi uses to deal with these issues that are not commonly addressed by many other musicians. This article analyses his lyrics and music to examine these particular issues. Particular attention is paid to music because the embedded subtexts of music help to illuminate the subtexts of the lyrics.