State-space prior distribution for parameter of nonhomogeneous Poisson spatiotemporal models.

This article proposes a new class of nonhomogeneous Poisson spatiotemporal model. In this approach, we use a state-space model-based prior distribution to handle the scale and shape parameters of the Weibull intensity function. The proposed prior distribution enables the inclusion of changes in the behavior of the intensity function over time. In defining the spatial correlation function of the model, we include anisotropy via spatial deformation. We estimate the model parameters from a Bayesian perspective, employ the Markov chain Monte Carlo approach, and validate this estimation procedure through a simulation exercise. Finally, the extreme rainfall in the southern semiarid region in northeastern Brazil is analyzed using the R10mm index. The proposed model showed better fit and prediction ability than did other nonhomogeneous Poisson spatiotemporal models available in the literature. This improvement in performance is mainly due to the flexibility of the intensity function that is achieved by allowing the incorporation, in time, of the climatic characteristics of this region.

Spatiotemporal nonhomogeneous poisson model with a seasonal component applied to the analysis of extreme rainfall.

This paper develops an extension of spatiotemporal models that handle count data using nonhomogeneous Poisson processes. In this new proposal, we incorporate a seasonal cycle component in the definition of the intensity function to control possible effects produced by the occurrence of the event of interest in regular periods. The seasonal cycle can cause problems in estimating the shape parameter of the Weibull and generalized Goel intensity functions. This shape parameter serves to confront the research hypothesis that seeks to identify a trend in the occurrence rate of an event of interest. In the case of the Weibull intensity function, a value significantly equal to one of the shape parameters indicates a constant rate of occurrence, less than one indicates a decreasing rate, and greater than one indicates an increasing rate. In the case of the Goel intensity function, parameter values less than or equal to one indicate a decreasing occurrence rate, and values greater than one indicate the presence of a change point. We also built a spatial model using the Musa-Okumoto intensity function as an alternative to approximate counting processes for which there is a decreasing trend in the occurrence rate of the event of interest. We estimated the parameters of the proposed method from a Bayesian perspective. Finally, we fitted the proposed model and compared it with other approximations to analyze the frequency of extreme rainfall in the northern region of the states of Maranhão and Piauí in northeastern Brazil over ten years. Among the main results, we found that (1) the proposed method has proven superior in terms of fit and prediction performance than the other models, and (2) unlike other approximations, the proposed model does not detect changes in the rate of extreme rainfall occurrences.

Use of a bayesian hierarchical model to study the allometric scaling of the fetoplacental weight ratio / Utilização de modelo hierárquico bayesiano para estudar a relação alométrica entre o peso placentário e peso ao nascer

Objectives: to propose the use of a Bayesian hierarchical model to study the allometric scaling of the fetoplacental weight ratio, including possible confounders. Methods: data from 26 singleton pregnancies with gestational age at birth between 37 and 42 weeks were analyzed. The placentas were collected immediately after delivery and stored under refrigeration until the time of analysis, which occurred within up to 12 hours. Maternal data were collected from medical records. A Bayesian hierarchical model was proposed and Markov chain Monte Carlo simulation methods were used to obtain samples from distribution a posteriori. Results: the model developed showed a reasonable fit, even allowing for the incorporation of variables and a priori information on the parameters used. Conclusions: new variables can be added to the modelfrom the available code, allowing many possibilities for data analysis and indicating the potential for use in research on the subject.

Objetivos: propor a utilização de um modelo Hierárquico Bayesiano para estudar a relação alométrica existente entre o peso ao nascer e o peso placentário, incluindo possíveis fatores interferentes. Métodos: foram analisados os dados de 26 gestações únicas, com idade gestacional entre 37 e 42 semanas. As placentas foram coletadas imediatamente após o parto e conservadas sob refrigeração até o momento da análise, o que ocorreu em até 12 horas. Os dados maternos foram obtidos de prontuários médicos. Finalmente, foi elaborado um modelo hierárquico bayesiano e, para obter amostras da distribuição a posteriori, foram utilizados métodos de simulação Markov Chain Monte Carlo. Resultados: o modelo obtido apresentou um ajuste razoável, permitindo ainda a incorporação de variáveis e informações a priori, sobre os parâmetros utilizados. Conclusões: a partir da disponibilização do código, novas variáveis podem ser adicionadas ao modelo, permitindo muitas possibilidades para a análise dos dados, mostrando potencial para ser utilizado em pesquisas na área.

Coronary artery disease in patients with rheumatic and non-rheumatic valvular heart disease treated at a public hospital in Rio de Janeiro.

OBJECTIVE: to estimate the prevalence of coronary artery disease (CAD) in valvular heart disease of rheumatic (RVHD) and non-rheumatic (NVHD) etiology, assessing possible predictive factors for the presence of CAD. METHODS: This is a cross-sectional study of a series of cases obtained from a pre-defined population, wherein 1,412 patients referred for heart surgery of any etiology were evaluated. Of these, 294 primary heart disease patients aged > or =40 submitted to cinecoronary arteriography (CA) were identified and studied. RESULTS: patients with RVHD presented lower prevalence of CAD (4%) when compared to NVHD (33.61%), p<0.0001. The logistic regression analysis showed that age, typical angina-like chest pain (TACP), systemic arterial hypertension (SAH), diabetes and dyslipidemia were significantly related to CAD, and that the rheumatic etiology was not a disease determinant. Smoking and gender were clinically important in CAD, although not statistically significant. In the whole group, the Log-linear analysis showed that, regardless of the etiology, gender, age > or =55, SAH, TACP, diabetes and dyslipidemia were all related directly to CAD, with the latter three being the most important variables for the disease. CONCLUSION: the prevalence of CAD among RVHD patients is low, whereas it is high among NVHD patients; the rheumatic etiology does not seem to have any beneficial effects on the prevalence of CAD; gender, age, SAH, TACP, dyslipidemia and diabetes were identified as being strongly associated with the presence of CAD. It is possible to define the criteria that indicate the need for pre-surgical CA in heart valve replacements, so that the standard indication after the age of 40 years can be avoided.

Doença arterial coronariana em pacientes com valvopatia reumática e não-reumática acompanhados em hospital público do Rio de Janeiro / Coronary artery disease in patients with rheumatic and non-rheumatic valvular heart disease treated at a public hospital in Rio de Janeiro

OBJETIVO: Avaliar a prevalência de doença arterial coronariana (DAC) na valvopatia de etiologia reumática e não-reumática, examinando possíveis fatores preditivos da presença da doença. MÉTODOS: Estudo transversal, de série de casos obtidos em população pré-definida. Foram avaliados 1.412 pacientes com indicação de cirurgia cardíaca por qualquer etiologia. Destes, foram encontrados e estudados 294 casos com valvopatia primária de etiologias reumática e não-reumática, com idade > 40 anos, submetidos a coronariografia. RESULTADOS: Os valvopatas reumáticos apresentaram menor prevalência de DAC (4 por cento) que os não-reumáticos (33,61 por cento) (p < 0,0001). O modelo de regressão logística evidenciou que idade, dor torácica típica, hipertensão arterial sistêmica (HAS), diabete melito e dislipidemia estavam significativamente relacionados à DAC, e que a etiologia reumática não era determinante da doença. Tabagismo e sexo revelaram-se de importância clínica na DAC, embora sem significância estatística. No grupo total, o modelo de análise Log linear demonstrou que, independentemente da etiologia, sexo, idade > 55 anos, HAS, dor torácica típica, diabete e dislipidemia se relacionavam diretamente com a DAC, sendo as três últimas as variáveis de maior peso para a doença. CONCLUSÃO: A prevalência de DAC é baixa entre valvopatas reumáticos e mais alta entre não-reumáticos; a etiologia reumática não parece exercer efeito protetor sobre a prevalência de DAC; e as variáveis sexo, idade, HAS, dor torácica típica, dislipidemia e diabete melito foram identificadas como fortemente associadas à presença de DAC. É possível definir critérios de indicação de coronariografia pré-operatória nas trocas valvares, podendo-se evitar a indicação rotineira a partir dos 40 anos.

OBJECTIVE: to estimate the prevalence of coronary artery disease (CAD) in valvular heart disease of rheumatic (RVHD) and non-rheumatic (NVHD) etiology, assessing possible predictive factors for the presence of CAD. METHODS: This is a cross-sectional study of a series of cases obtained from a pre-defined population, wherein 1,412 patients referred for heart surgery of any etiology were evaluated. Of these, 294 primary heart disease patients aged >40 submitted to cinecoronary arteriography (CA) were identified and studied. RESULTS: patients with RVHD presented lower prevalence of CAD (4 percent) when compared to NVHD (33.61 percent), p<0.0001. The logistic regression analysis showed that age, typical angina-like chest pain (TACP), systemic arterial hypertension (SAH), diabetes and dyslipidemia were significantly related to CAD, and that the rheumatic etiology was not a disease determinant. Smoking and gender were clinically important in CAD, although not statistically significant. In the whole group, the Log-linear analysis showed that, regardless of the etiology, gender, age >55, SAH, TACP, diabetes and dyslipidemia were all related directly to CAD, with the latter three being the most important variables for the disease. CONCLUSION: the prevalence of CAD among RVHD patients is low, whereas it is high among NVHD patients; the rheumatic etiology does not seem to have any beneficial effects on the prevalence of CAD; gender, age, SAH, TACP, dyslipidemia and diabetes were identified as being strongly associated with the presence of CAD. It is possible to define the criteria that indicate the need for pre-surgical CA in heart valve replacements, so that the standard indication after the age of 40 years can be avoided.