Uma avaliação do uso de um modelo contínuo na análise de dados discretos de sobrevivência

Propomos neste trabalho uma comparação dos resultados de análises de dados de sobrevivência utilizando dois modelos equivalentes, sendo um contínuo e outro discreto. Diz-se “modelos equivalentes” pois será utilizado um modelo cuja formulação original é contínua e através deste modelo, será gerado um modelo discreto correspondente

Analysis of the camoufage effect in time of segregation in texturized regions using the Cox proportional hazard model

Os seres humanos possuem visão tricromática. No entanto, variações nos genes podem provocar defciências na visão em cores levando ao dicromatismo. O objetivo deste trabalho foi verifcar a real efciência dos dicromatas na quebra de camufagem por cor. Participaram desse estudo nove indivíduos daltônicos e a resposta foi o tempo de segregação de alvos camufados. O interesse foi comparar o tempo de resposta em várias condições de camufagem e a análise dos dados foi realizada utilizando o modelo de riscos proporcionais de Cox. ____________________________________________________________________________________________________________________ ABSTRACTHumans have trichromatic vision. However variations in gene can cause defciency in color vision resulting to dichromatism. The aim of this work was to verify the real effciency of dichromats to break colour camoufage. Total of nine colour-blind individuals participated in this study and the variable considered was the time to segregation of camoufaged targets. The interest was to compare the response time in several conditions of camoufage and the analysis was performed using the Cox proportional hazard model

CONSEQUENCES OF ALCOHOL ABUSE/DEPENDENCE IN BRAZIL: DISABILITY-ADJUSTED LIFE YEARS (DALY)

This study estimated the burden of alcohol use in Disability-Adjusted Life Years (DALY) for Brazil. The measures of DALY combines the measures of Years of Life Lost (YLL) and Years Lived with Disability (YLD), based on methodology of the Global Burden of Disease (GBD) and were presented using the rate of 1:10,000. Alcohol use was defined by ICD-10 F10-F10.9. We used outpatient treatment, admissions and mortality data and the disability weights specific for alcohol according with GBD to calculate the DALY-relevant measures. The total value of DALY in Brazil due to the alcohol use was 32.05, similar to what we observed in YLD total value [31.60] and different of the measure of the YLL total value [0.45]. There is important difference in DALY’s value between gender, being the biggest at the age group 40-44 [158.10 male and 34.03 female]. The biggest loss of DALY’s total value is at the 44 age group with 158.01 years. The impact of the DALY due to alcohol use represents the need to refine existing actions in prevention and treatment, seeking the search for better strategies that promote more responsible alcohol use and decrease individual and social harms

ESTIMAÇÃO INTERVALAR PARA OS PARÂMETROS DO MODELO EXPONENCIAL DISCRETO: UMA APLICAÇÃO PARA DADOS DE SOBREVIVÊNCIA

Este trabalho apresenta a utilização do modelo exponencial discreto (modelo geométrico) na análise de dados discretos, em particular, para dados de sobrevivência. Foram apresentadas a estimativa pontual e seus respectivos intervalos de confiança para o parâmetro do modelo. Este trabalho considerou a técnica de reamostragem bootstrap (paramétrica e não-paramétrica) como um procedimento alternativo adequado para construção de intervalos de confiança para o parâmetro do modelo exponencial discreto. A metodologia foi ilustrada através de dados simulados e por meio de uma aplicação em um conjunto de dados reais sobre o tempo até a rehospitalização de pacientes com esquizofrenia. Todos os procedimentos de estimação e simulações foram realizados através do software livre R

Inferência bayesiana no modelo Weibull discreto em dados com presença de censura

Este trabalho apresenta uma inferência bayesiana da distribuição Weibull discreta em dados com presença de censuras. Foi proposto também um teste de significância genuinamente bayesiano (FBST - Full Bayesian Significance Test) para testar seu parâmetro de forma. Amostras da distribuição a posteriori dos parâmetros foram obtidas por meio de simulações via Markov Chain Monte Carlo (MCMC). A metodologia desenvolvida foi ilustrada em simulações e aplicada em um conjunto de dados sobre o tempo de sobrevivência de homens diagnosticados com AIDS. Todas as simulações e obtenções das estimativas foram realizadas com a linguagem R.This work presents a bayesian inference on discrete Weibull distribution with censored data. A Full Bayesian Significance Test (FBST) was proposed to test the shape parameter of model. Samples from the posterior distributions of parameters were numerically obtained by Markov Chain Monte Carlo (MCMC) simulations. This methodology was illustrated using simulated data and by application on a real database of survival times of men diagnosed with AIDS. All simulations and estimates were performed in R language

Brazilian vegetarians diet quality markers and comparison with the general population : a nationwide cross-sectional study

Background Vegetarianism is an increasingly common practice worldwide. Despite good evidence from other countries regarding vegetarians’ diet quality, data from the Brazilian population is still scarce. Objective To characterize the vegetarian Brazilian population and evaluate their diet quality compared to the general Brazilian population. Methods We performed a nationwide cross-sectional study using an online self-administered questionnaire, previously validated for the Brazilian population, to evaluate diet quality markers of vegetarians. The invitation to participate in the survey was spread nationwide, aimed at vegetarian communities. Individuals who considered themselves vegetarians and were at least 18 years old were eligible to participate. The results on regular intake and intake adequacy were compared among vegetarians and between genders using the Pearson’s chi-square test. The body mass index (BMI) were analyzed by the Analysis of Variance (ANOVA) followed by Tukey post-hoc test. The Kolmogorov-Smirnov test verified normality. All analyses considered bilateral hypotheses and a significance level of 5% (p <0.05). Results Brazilian vegetarians presented better diet quality markers, such as higher regular weekly intake and adequate daily intake of fruits and vegetables, and lower regular intake of soft drinks when compared to the general Brazilian population. Vegetarians also presented a proportionally higher consumption of natural foods and lower consumption of processed foods. Among vegetarians, a higher proportion of vegans showed positive results regarding diet markers analysis, when compared to vegetarians, pesco-vegetarians, and semi-vegetarians. Conclusions Vegetarians showed better results of diet adequacy when compared to the general population in Brazil, and vegans fared better when compared with other vegetarians. Despite the good results found, a large proportion of the participants still did not achieve the fruits and vegetables daily intake, according to the World Health Organization recommendations

Testing allele homogeneity: the problem of nested hypotheses

Background: The evaluation of associations between genotypes and diseases in a case-control framework plays an important role in genetic epidemiology. This paper focuses on the evaluation of the homogeneity of both genotypic and allelic frequencies. The traditional test that is used to check allelic homogeneity is known to be valid only under Hardy-Weinberg equilibrium, a property that may not hold in practice. Results: We first describe the flaws of the traditional (chi-squared) tests for both allelic and genotypic homogeneity. Besides the known problem of the allelic procedure, we show that whenever these tests are used, an incoherence may arise: sometimes the genotypic homogeneity hypothesis is not rejected, but the allelic hypothesis is. As we argue, this is logically impossible. Some methods that were recently proposed implicitly rely on the idea that this does not happen. In an attempt to correct this incoherence, we describe an alternative frequentist approach that is appropriate even when Hardy-Weinberg equilibrium does not hold. It is then shown that the problem remains and is intrinsic of frequentist procedures. Finally, we introduce the Full Bayesian Significance Test to test both hypotheses and prove that the incoherence cannot happen with these new tests. To illustrate this, all five tests are applied to real and simulated datasets. Using the celebrated power analysis, we show that the Bayesian method is comparable to the frequentist one and has the advantage of being coherent. Conclusions: Contrary to more traditional approaches, the Full Bayesian Significance Test for association studies provides a simple, coherent and powerful tool for detecting associations

Brazilian vegetarian population — influence of type of diet, motivation and sociodemographic variables on quality of life measured by specific tool (VEGQOL)

The adoption of a vegetarian diet has been associated with positive health outcomes. However, few studies evaluate the effect of this eating pattern on quality of life. Moreover, no specific instrument for the vegetarian population to measure the quality of life is available worldwide. Therefore, this study aimed to elaborate and validate a specific questionnaire to measure the quality of life in vegetarians. The Specific Vegetarian Quality of Life Questionnaire (VEGQOL) was constructed based on other instruments and studies related to vegetarianism. The content and semantic validation were performed by a group of experts, followed by a pilot study to evaluate the questionnaire acceptability and reproducibility. Discriminant validation was tested using the WHOQOL as the gold standard measure (Pearson correlation ranging from 0.302 of the domain 3 to 0.392 of the domain 2). Afterward, a nationwide survey was conducted using VEGQOL. Content and semantic validation selected 19 of the initial 30 items. VEGQOL presented good reproducibility (Cohen’s Kappa coefficient ranging from 0.361 to 0.730 and intraclass correlation coefficient of 0.820) and internal consistency (0.708), both adequate to evaluate the quality of life in vegetarians. The sample size (n = 5014 individuals, error of 3% at a level of significance of 5%) and distribution was representative of the Brazilian vegetarian population. In general, the quality of life of Brazilian vegetarians was considered satisfactory (VEGQOL cut off points 70–80). Among different types of vegetarians, the vegans showed better results with a VEGQOL mean value of 79.2 ± 10.7. Older individuals, the ones who adopted the diet for a longer time (VEGQOL mean value of 75.8 ± 12.7) and the ones who had other vegetarians in their social network (VEGQOL mean value of 74.6 ± 12.2) also had a better quality of life score. Individuals who adopted it for ethical or health reasons had a higher quality of life score. The questionnaire produced in this study is a useful tool for future research in this area. Results were better for vegans and for the ones who adopt the diet for ethical or health reasons