ABSTRACT
Indigenous societies are known to have occupied the Amazon basin for more than 12,000 years, but the scale of their influence on Amazonian forests remains uncertain. We report the discovery, using LIDAR (light detection and ranging) information from across the basin, of 24 previously undetected pre-Columbian earthworks beneath the forest canopy. Modeled distribution and abundance of large-scale archaeological sites across Amazonia suggest that between 10,272 and 23,648 sites remain to be discovered and that most will be found in the southwest. We also identified 53 domesticated tree species significantly associated with earthwork occurrence probability, likely suggesting past management practices. Closed-canopy forests across Amazonia are likely to contain thousands of undiscovered archaeological sites around which pre-Columbian societies actively modified forests, a discovery that opens opportunities for better understanding the magnitude of ancient human influence on Amazonia and its current state.
Subject(s)
Archaeology , Forests , Humans , BrazilABSTRACT
This article proposes a modeling approach for handling spatial heterogeneity present in the study of the geographical pattern of deaths due to cerebrovascular disease.The framework involvesa point pattern analysis with components exhibiting spatial variation. Preliminary studies indicate that mortality of this disease and the effect of relevant covariates do not exhibit uniform geographic distribution. Our model extends a previously proposed model in the literature that uses spatial and non-spatial variables by allowing for spatial variation of the effect of non-spatial covariates. A number of relative risk indicators are derived by comparing different covariate levels, different geographic locations, or both. The methodology is applied to the study of the geographical death pattern of cerebrovascular deaths in the city of Rio de Janeiro. The results compare well against existing alternatives, including fixed covariate effects. Our model is able to capture and highlight important data information that would not be noticed otherwise, providing information that is required for appropriate health decision-making.
Subject(s)
Cerebrovascular Disorders/mortality , Models, Statistical , Biostatistics/methods , Brazil/epidemiology , Humans , Multivariate Analysis , Normal Distribution , Proportional Hazards Models , Regression Analysis , RiskABSTRACT
The aim of this study was to investigate excess mortality from dengue in Greater Metropolitan Rio de Janeiro, Brazil, during an epidemic in 2007-2008. A Poisson dynamic model was tested to predict the number of deaths during these epidemic years. Inference was conducted with a Bayesian approach. Excess mortality was detected in March 2008 in children < 15 years. In addition, the highest number of reported dengue cases in Rio de Janeiro was in March and April 2008. Since the increase in mortality should be preceded by an increase in morbidity, one can hypothesize that there was excess mortality from dengue in children during the epidemic in Greater Metropolitan Rio de Janeiro in March 2008.
Subject(s)
Dengue/mortality , Epidemics/statistics & numerical data , Adolescent , Aged , Aged, 80 and over , Bayes Theorem , Brazil/epidemiology , Child , Child, Preschool , Communicable Diseases/diagnosis , Communicable Diseases/mortality , Diagnosis, Differential , Humans , Infant , Middle Aged , Young AdultABSTRACT
O objetivo deste estudo é investigar a ocorrência de sobremortalidade durante a epidemia de dengue ocorrida na Região Metropolitana do Rio de Janeiro, Brasil, entre 2007 e 2008. Para obter a predição dos óbitos desses anos epidêmicos, um modelo dinâmico Poisson foi ajustado aos dados de mortalidade por dengue e por doenças que fazem parte do seu diagnóstico diferencial. Toda a inferência foi realizada sob o paradigma bayesiano. Verificou-se um excesso de mortalidade em março de 2008, em menores de 15 anos de idade. Paralelamente, em março e abril de 2008, houve o maior número de casos notificados de dengue no Estado do Rio de Janeiro. Considerando que o aumento da mortalidade deve ser precedido por um incremento na morbidade, pode-se levantar a hipótese de que houve um excesso de mortalidade por dengue em crianças na epidemia de dengue ocorrida na Região Metropolitana do Rio de Janeiro, em março de 2008.
The aim of this study was to investigate excess mortality from dengue in Greater Metropolitan Rio de Janeiro, Brazil, during an epidemic in 2007-2008. A Poisson dynamic model was tested to predict the number of deaths during these epidemic years. Inference was conducted with a Bayesian approach. Excess mortality was detected in March 2008 in children < 15 years. In addition, the highest number of reported dengue cases in Rio de Janeiro was in March and April 2008. Since the increase in mortality should be preceded by an increase in morbidity, one can hypothesize that there was excess mortality from dengue in children during the epidemic in Greater Metropolitan Rio de Janeiro in March 2008.
El objetivo de este estudio es investigar el exceso de mortalidad durante la epidemia de dengue de 2007 y 2008 en la región metropolitana de Río de Janeiro, Brasil. Con el fin de predecir el número de muertes durante estos años de epidemia, un modelo de Poisson dinámico fue ajustado a los datos de mortalidad por dengue y enfermedades que son parte del diagnóstico diferencial. La inferencia se realizó bajo el paradigma bayesiano. Hubo un exceso de mortalidad en niños menores de 15 años de edad en marzo de 2008. Además, en marzo y abril de 2008, se produjo el mayor número de casos de dengue en el estado de Río de Janeiro. Considerando que el aumento de la mortalidad debe ser precedido por un aumento de la morbilidad, se puede plantear la hipótesis de que hubo un exceso de mortalidad por dengue en niños durante la epidemia de dengue que se produjo en el área metropolitana de Río de Janeiro en marzo de 2008.
Subject(s)
Adolescent , Aged , Aged, 80 and over , Child , Child, Preschool , Humans , Infant , Middle Aged , Young Adult , Dengue/mortality , Epidemics/statistics & numerical data , Bayes Theorem , Brazil/epidemiology , Communicable Diseases/diagnosis , Communicable Diseases/mortality , Diagnosis, DifferentialABSTRACT
This research describes a new Bayesian spatiotemporal model to analyse block-design BOLD fMRI studies. In the temporal dimension, we parameterise the hemodynamic response function's (HRF) shape with a potential increase of signal and a subsequent exponential decay. In the spatial dimension, we use Gaussian Markov random fields (GMRF) priors on activation characteristics parameters (location and magnitude) that embody our prior knowledge that evoked responses are spatially contiguous and locally homogeneous. The result is a spatiotemporal model with a small number of parameters, all of them interpretable. Simulations from the model are performed in order to ascertain the performance of the sampling scheme and the ability of the posterior to estimate model parameters, as well as to check the model sensitivity to signal to noise ratio. Results are shown on synthetic data and on real data from a block-design fMRI experiment.
Subject(s)
Bayes Theorem , Image Processing, Computer-Assisted/statistics & numerical data , Magnetic Resonance Imaging/statistics & numerical data , Algorithms , Computer Simulation , Humans , Markov Chains , Models, Statistical , Normal DistributionABSTRACT
In this paper, we propose a new class of semi-parametric cure rate models. Specifically, we construct dynamic models for piecewise hazard functions over a finite partition of the time axis. Allowing the size of partition and the levels of baseline hazard to be random, our proposed models provide a great flexibility in controlling the degree of parametricity in the right tail of the survival distribution and the amount of correlations among the log-baseline hazard levels. Several properties of the proposed models are derived, and propriety of the implied posteriors with improper noninformative priors for regression coefficients based on the proposed models is established for the fixed partition of the time axis. In addition, an efficient reversible jump computational algorithm is developed for carrying out posterior computation. A real data set from a melanoma clinical trial is analyzed in detail to further demonstrate the proposed methodology.
Subject(s)
Bayes Theorem , Proportional Hazards Models , Survival Analysis , Biometry/methods , Clinical Trials as Topic , Humans , Melanoma/epidemiology , Melanoma/mortality , Remission Induction , Treatment OutcomeABSTRACT
In many survival studies, covariates effects are time-varying and there is presence of spatial effects. Dynamic models can be used to cope with the variations of the effects and spatial components are introduced to handle spatial variation. This paper proposes a methodology to simultaneously introduce these components into the model. A number of specifications for the spatial components are considered. Estimation is performed via a Bayesian approach through Markov chain Monte Carlo methods. Models are compared to assess relevance of their components. Analysis of a real data set is performed, showing the relevance of both time-varying covariate effects and spatial components. Extensions to the methodology are proposed along with concluding remarks.
Subject(s)
Models, Statistical , Survival Analysis , Bayes Theorem , Biometry , Brazil , Humans , Markov Chains , Monte Carlo Method , Proportional Hazards Models , Salaries and Fringe Benefits/statistics & numerical dataABSTRACT
OBJETIVO: O objetivo deste trabalho é analisar a existência de variações na indicação terapêutica a pacientes com fratura proximal de fêmur entre os hospitais conveniados com o SUS e entre pacientes socialmente distintos. MÉTODO: Foram analisados os dados do SIH-SUS dos hospitais do município do Rio de Janeiro, 1994-1995. RESULTADO: A análise multivariada mostrou que as chances de cirurgia foram maiores para as mulheres (OR=1,53, IC95 por cento1,18-1,99); menores para os hospitais federais (OR = 0,21, IC95 por cento 0,10-0,41), estaduais (OR =0,07, IC95 por cento 0,04-0,12) e municipais (OR=0,11, IC95 por cento 0,07-0,18), em comparação com o hospital privado contratado pelo SUS; foram menores nas emergências (OR=0,31, IC95 por cento 0,19-0,48); e foram maiores nos hospitais localizados em áreas mais privilegiadas (OR=1,68, IC95 por cento 1,52-1,86). CONCLUSÃO: A configuração dos mercados variou com o perfil dos hospitais e pacientes, e a indicação de cirurgia foi associada a fatores não relacionados com a necessidade, mostrando diferenças no acesso ao tratamento adequado.
OBJECTIVE: The aim of this study was to analyze the variations in the surgical use of healthcare services for hip fracture patients, and the occurrence of inequity in the Rio de Janeiro Public Health Sector. METHODS: The Unified Health System Hospital Information System data from hospital records of Rio de Janeiro health services between 1994 and 1995 were analyzed. RESULTS: Multivariate analysis showed that women had a greater chance of surgery (OR=1.53, CI95 percent1.18-199). The chances of surgery were lower in federal hospitals (OR=0.21, CI95 percent 0.10-0.41), state hospitals (OR =0.07, CI95 percent 0.04-0.12), and city hospitals (OR=0.11, CI95 percent 0.07-0.18), compared with private hospitals hired by the SUS. The chances of surgery were lower in emergency departments (OR=0.31, CI95 percent 0.19-0.48) and in hospitals located in less deprived areas (OR=1.68, CI95 percent 1.52-1.86). CONCLUSION: The variation in the hospital market was related to patient and hospital profiles, and the surgical treatment for hip fracture was associated with factors unrelated to need, showing differences in access.
Subject(s)
Health Services Research , Femoral Fractures , Health Inequities , Health ServicesABSTRACT
Desenvolveu-se um método de construçäo de mercados hospitalares em regiäo urbana, considerando os pacientes que sofreram fratura de colo do fêmur e que foram internados durante o período de 1994-1995 em hospitais do município do Rio de Janeiro financiados pelo Sistema Unico de Saúde (SUS). Utilizou-se técnica de alisamento espacial, a partir da estimativa de Kernel (quártico) para construçäo de áreas de atendimento de cada hospital e, posteriormente, dos mercados hospitalares. Foram apresentadas áreas do município nas quais houve domínio do mercado e domínio secundário no atendimento de pacientes com fratura de colo de fêmur. O estudo de mercados hospitalares pode auxiliar o planejador de saúde na busca de realocaçöes mais eficientes durante o processo de alocaçäo de recursos.
