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» Resultado: 2 registros
| Registro 1 de 2 | |
| Autor: | Brumback, Babette - Greenland, Sander - Redman, Mary - Kiviat, Nancy - Diehr, Paula - |
| Título: | The intensity-score approach to adjusting for confounding |
| Fuente: | Biometrics. v.59, n.2. International Biometric Society |
| Páginas: | pp. 274-285 |
| Año: | jun. 2003 |
| Resumen: | In a recent article on the efficacy of antihypertensive therapy, Berlowitz et al. (1998, New England Journal of Medicine 339, 1957-1963) introduced an ad hoc method of adjusting for serial confounding assessed via an intensity score, which records cumulative differences over time between therapy actually received and therapy predicted by prior medical history. Outcomes are subsequently regressed on the intensity score and baseline covariates to determine whether intense treatment or exposure predicts a favorable response. We use a structural nested mean model to derive conditions sufficient for interpreting the Berlowitz results causally. We also consider a modified approach that scales the intensity at each time by the inverse expected treatment given prior medical history. This leads to a simple, two-step implementation of G-estimation if we assume a nonstandard but useful structural nested mean model in which subjects less likely to receive treatment are more likely to benefit from it. These modeling assumptions apply, for example, to health services research contexts in which differential access to care is a primary concern. They are also plausible in our analysis of the causal effect of potent antiretroviral therapy on change in CD4 cell count, because men in the sample who are less likely to initiate treatment when baseline CD4 counts are high are more likely to experience large positive changes. We further extend the methods to accomodate repeated outcomes and time-varying effects of time-varying exposures. |
| Solicitar por: | HEMEROTECA B + datos de Fuente |
| Registro 2 de 2 | |
| Autor: | Greenland, Sander - |
| Título: | Generalized conjugate priors for bayesian analysis of risk and survival regressions |
| Fuente: | Biometrics. v.59, n.1. International Biometric Society |
| Páginas: | pp. 92-99 |
| Año: | mar. 2003 |
| Resumen: | Conjugate priors for Bayesian analyses of relative risks can be quite restrictive, because their shape depends on their location. By introducing a separate location parameter, however, these priors generalize to allow modeling of a broad range of prior opinions, while still preserving the computational simplicity of conjugate analyses. The present article illustrates the resulting generalized conjugate analyses using examples from case-control studies of the association of residential wire codes and magnetic fields with childhood leukemia. |
| Solicitar por: | HEMEROTECA B + datos de Fuente |
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