Browsing by Author "Silva, Giovani L."
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- Análise Bayesiana espacial conjunta de dados longitudinais e de sobrevivência com aplicação ao estudo do VIH/SIDA no BrasilPublication . Martins, Rui; Silva, Giovani L.; Andreozzi, Valeska"A análise conjunta dos dados longitudinais e de sobrevivência tem suscitado muito interesse nos últimos anos, especialmente para dados relativos ao VIH/SIDA. Tradicionalmente, estes dados eram analisados considerando separadamente o tempo-até-evento (análise de sobrevivência) e as medições repetidas de biomarcadores (análise longitudinal). Mas, tendo em conta que os dados são observados num mesmo indivíduo, a modelação conjunta das respostas subjacentes parece ser mais apropriada. O modelo conjunto espacial bayesiano aqui proposto apresenta melhorias consideráveis nas distribuições do tempo mediano de sobrevivência quando comparado com o modelo separado."
- Bayesian joint modeling of longitudinal and spatial survival AIDS dataPublication . Martins, Rui; Silva, Giovani L.; Andreozzi, Valeska"Joint analysis of longitudinal and survival data has received increasing attention in the recent years, especially for analyzing cancer and AIDS data. As both repeated measurements (longitudinal) and time-to-event (survival) outcomes are observed in an individual, a joint modeling is more appropriate because it takes into account the dependence between the two types of responses, which are often analyzed separately. We propose a Bayesian hierarchical model for jointly modeling longitudinal and survival data considering functional time and spatial frailty effects, respectively. That is, the proposed model deals with nonlinear longitudinal effects and spatial survival effects accounting for the unobserved heterogeneity among individuals living in the same region. This joint approach is applied to a cohort study of patients with HIV/AIDS in Brazil during the years 2002–2006. Our Bayesian joint model presents considerable improvements in the estimation of survival times of the Brazilian HIV/AIDS patients when compared with those ones obtained through a separate survival model and shows that the spatial risk of death is the same across the different Brazilian states."