RESUMO
In this paper, we estimate the dynamic parameters of a time-varying coefficient model through radial kernel functions in the context of a longitudinal study. Our proposal is based on a linear combination of weighted kernel functions involving a bandwidth, centered around a given set of time points. In addition, we study different alternatives of estimation and inference including a Frequentist approach using weighted least squares along with bootstrap methods, and a Bayesian approach through both Markov chain Monte Carlo and variational methods. We compare the estimation strategies mention above with each other, and our radial kernel functions proposal with an expansion based on regression spline, by means of an extensive simulation study considering multiples scenarios in terms of sample size, number of repeated measurements, and subject-specific correlation. Our experiments show that the capabilities of our proposal based on radial kernel functions are indeed comparable with or even better than those obtained from regression splines. We illustrate our methodology by analyzing data from two AIDS clinical studies.
RESUMO
El denominado análisis de datos longitudinales (ADL) se refiere a los métodos para evaluar de manera apropiada las medidas de un mismo sujeto que se repiten en el tiempo. El ADL es una herramienta adecuada para entender indicadores de cambio en procesos de salud y enfermedad y para la evaluación del efecto de diversas intervenciones terapéuticas. Se presentan los principales modelos de ADL, sus ventajas y algunos ejemplos recientes de la literatura médica.
Longitudinal data analysis (LDA) refers to the methods designed to evaluate repeated measurements within an individual. LDA is an appropriate tool to address the process of change in health and disease and also to evaluate the efficacy of interventions. We present the main LDA models as well as their advantages and some clinical examples from recent medical literature.
A denominada análise de dados longitudinais (ADL) refere-se aos métodos para avaliar de maneira apropriada as medidas de um mesmo sujeito que se repetem no tempo. O ADL é uma ferramenta adequada para entender indicadores de mudança em processos de saúde e doença e para a avaliação do efeito de diversas intervenções terapêuticas. Apresentam-se os principais modelos de ADL, suas vantagens e alguns exemplos recentes da literatura médica.