Variable selection for survival models based on penalized likelihood

A seleção de variáveis é uma importante fase para a construção de um modelo parcimonioso. Entretanto, as técnicas mais populares de seleção de variáveis, como, por exemplo, a seleção do melhor subconjunto de variáveis e o método stepwise, ignoram erros estocásticos inerentes à fase de seleção das variáveis. Neste trabalho, foram estudados procedimentos alternativos aos métodos mais populares para o modelo de riscos proporcionais de Cox e o modelo de Cox com fragilidade gama. Os métodos alternativos são baseados em verossimilhançaa penalizada e diferem dos métodos usuais de seleção de variáveis, pois têm como objetivo excluir do modelo variáveis não significantes estimando seus coeficientes como zero. O estimador resultante possui propriedades desejáveis com escolhas apropriadas de funções de penalidade e do parâmetro de suavização. A avaliação desses métodos foi realizada por meio de simulação e uma aplicação a um conjunto de dados reais foi considerada.Variable selection is an important step when setting a parsimonious model. However, the most popular variable selection techniques, such as the best subset variable selection and the stepwise method, do not take into account inherent stochastic errors in the variable selection step. This work presents a study of alternative procedures to more popular methods for the Cox proportional hazards model and the frailty model. The alternative methods are based on penalized likelihood and differ from the usual variable selection methods, since their objective is to exclude from the model non significant variables, estimating their coefficient as zero. The resulting estimator has nice properties with appropriate choices of penalty functions and the tuning parameter. The assessment of these methods was studied through simulations, and an application to a real data set was considered

Efficacy and safety of brand-risperidone versus similar-risperidone in elderly patients with neuropsychiatric disorders A retrospective study

Abstract -To compare the efficacy and tolerability of brand-risperidone against similar-risperidone in elderly outpatients. Method: The medical files of 16 elderly outpatients from the IPq-HCFMUSP treated with two formulations of risperidone (brand and similar) between July/1999 and February/2000 were reviewed. Two independent raters, using the Clinical Global Impression scale, evaluated the efficacy of the treatment with risperidone and the frequency of adverse effects. Results: Comparing October/1999 to November/1999, Rater 1 observed a trend (p=0.059) and Rater 2 found a statistically significant difference, in favor of the brand-risperidone group (p=0.014). Comparing October/1999 to February/2000, Rater 1 observed no statistically significant difference (p=0.190), but the Rater 2 found a statistically significant difference in favor of the brand-risperidone group (p=0.029). Comparing November/1999 to February/2000, both raters found no statistically significant differences between both risperidone formulations. Regarding adverse effects, a statistically significant difference (p=0.046) was found in favor of the patients treated with brand-risperidone. Conclusions: The risperidonereference, compared to similar-risperidone, showed a trend toward greater efficacy and tolerability. Key words: risperidone, elderly, treatment, efficacy, side effects. Eficácia e segurança da risperidona-referência versus risperidona-similar em pacientes idosos com transtornos neuropsiquiátricos: um estudo retrospectivo Resumo -Comparar a eficácia e a tolerabilidade da risperidona-referência versus a risperidona-similar em pacientes idosos. Métodos: Os prontuários de 16 pacientes do IPq-HCFMUSP tratados com duas formulações de risperidona (referência e similar) entre julho/1999 e fevereiro/2000 foram revisados. Dois examinadores independentes, utilizando a escala de Impressão Clínica Global, avaliaram a eficácia do tratamento com risperidona e a freqüência de efeitos colaterais. Resultados: Comparando outubro/1999 e novembro/1999, o avaliador 1 observou uma tendência (p=0,059) e o examinador 2 encontrou uma diferença estatisticamente significativa a favor da risperidona-referência (p=0,014). Comparando outubro/99 com fevereiro/2000, o avaliador 1 não encontrou diferença estatisticamente significativa (p=0,190), mas o examinador 2 encontrou uma diferença estatisticamente significativa a favor da risperidona-referência (p=0,029). Entre novembro/1999 e fevereiro/2000, ambos examinadores não encontraram diferença significativas entre as formulações. Quanto aos efeitos colaterais, houve diferença significativa (p=0,046) a favor do grupo risperidona-referência. Conclusões: A risperidonareferência, quando comparada à risperidona-similar, mostrou tendência a maior eficácia e tolerabilidade

Efficacy and safety of brand-risperidone versus similar-risperidone in elderly patients with neuropsychiatric disorders: A retrospective study

Abstract To compare the efficacy and tolerability of brand-risperidone against similar-risperidone in elderly outpatients. Method: The medical files of 16 elderly outpatients from the IPq-HCFMUSP treated with two formulations of risperidone (brand and similar) between July/1999 and February/2000 were reviewed. Two independent raters, using the Clinical Global Impression scale, evaluated the efficacy of the treatment with risperidone and the frequency of adverse effects. Results: Comparing October/1999 to November/1999, Rater 1 observed a trend (p=0.059) and Rater 2 found a statistically significant difference, in favor of the brand-risperidone group (p=0.014). Comparing October/1999 to February/2000, Rater 1 observed no statistically significant difference (p=0.190), but the Rater 2 found a statistically significant difference in favor of the brand-risperidone group (p=0.029). Comparing November/1999 to February/2000, both raters found no statistically significant differences between both risperidone formulations. Regarding adverse effects, a statistically significant difference (p=0.046) was found in favor of the patients treated with brand-risperidone. Conclusions: The risperidone-reference, compared to similar-risperidone, showed a trend toward greater efficacy and tolerability

Prevalence and correlates of alcoholism in community-dwelling elderly living in Sao Paulo, Brazil

Objectives To assess the prevalence of alcoholism in elderly living in the city of Sao Paulo (Brazil) and investigate associated risk factors. Methods A total of 1,563 individuals aged 60 years or older, of both genders of three districts of different socioeconomic classes (high, medium and low) in the city of Sao Paulo (Brazil) were interviewed. The CAGE screening test for alcoholism was applied and a structured interview was used to assess associated sociodemographic and clinical factors. The tests Mini Mental State Examination, Fuld Object Memory Evaluation, The Informant Questionnaire on Cognitive Decline in the Elderly and Bayer-Activities of Daily Living Scale were used for cognitive and functional assessment. Results Prevalence of alcoholism was 9.1%. Multivariate regression analysis showed that alcoholism was associated with male gender, `mulatto` ethnicity, smoking, and cognitive and functional impairment. In addition, the younger the individual and the lower the schooling level, the higher the risk for alcoholism. Conclusions The results obtained in this study show that alcoholism is highly frequent in the community-dwelling elderly living in Sao Paulo, and that it is associated with socio-demographic and clinical risk factors similar to those reported in the literature. This suggests that alcoholism in the elderly of a developing country shares the same basic characteristics seen in developed countries. These findings suggest that it is essential for health services and professional to be prepared to meet this demand that will significantly grow in the next years, especially in developing countries, where the rates of population aging are higher than those of developed countries. Copyright (C) 2009 John Wiley & Sons, Ltd.`Fundacao de Apoio a Pesquisa do Estado de Sao Paulo` (FAPESP)[01/05959-7