56 documents found, page 1 of 6
Wound healing and healing process in patients with diabetic foot ulcers: A surv...
Pereira, M. Graça; Vilaça, Margarida; Pedras, Susana; Carvalho, André; Vedhara, Kavita; Dantas, M. Jesus; Machado, Luís MeiraAims: This study aimed to identify demographic, clinical, and psychological contributors to DFU healing and favorable healing process. Methods: Patients with a chronic DFU were evaluated at baseline (T0; n = 153), two months later (T1; n = 108), and six months later (T2; n = 71). Patients were evaluated on health literacy, perceived stress, anxiety, depression, and illness perceptions. Cox proportional hazard m...
Nonparametric estimation of the distribution of gap times for recurrent events
Soutinho, Gustavo; Machado, Luís MeiraIn many longitudinal studies, information is collected on the times of different kinds of events. Some of these studies involve repeated events, where a subject or sample unit may experience a well-defined event several times throughout their history. Such events are called recurrent events. In this paper, we introduce nonparametric methods for estimating the marginal and joint distribution functions for recurr...
Analysis of complex survival data: a tutorial using the Shiny MSM.app application
Gustavo Soutinho; Machado, Luís MeiraThe development of applications for obtaining interpretable results in a simple and summarized manner in multi-state models is a research field with great potential, namely in terms of using open source tools that can be easily implemented in biomedical applications. In this tutorial, we introduce MSM.app, an interactive web application using the Shiny package for the R language. In the following sections, we p...
A method for determining groups in nonparametric regression curves: application...
Roca-Pardiñas, Javiez; Ordóñez, Celestino; Machado, Luís MeiraGeneralized additive models provide a flexible and easily-interpretable method for uncovering a nonlinear relationship between response and covariates. In many situations, the effect of a continuous covariate on the response varies across groups defined by the levels of a categorical variable. When confronted with a considerable number of groups defined by the levels of the categorical variable and a factor‐by‐...
Methods for checking the Markov condition in multi-state survival data
Soutinho, Gustavo; Machado, Luís MeiraThe inference in multi-state models is traditionally performed under a Markov assumption that claims that past and future of the process are independent given the present state. This assumption has an important role in the estimation of the transition probabilities. When the multi-state model is Markovian, the Aalen-Johansen estimator gives consistent estimators of the transition probabilities but this is no lo...
Parametric landmark estimation of the transition probabilities in survival data...
Soutinho, Gustavo; Machado, Luís MeiraMulti-state models are a useful tool for analyzing survival data with multiple events. The transition probabilities play an important role in these models since they allow for long-term predictions of the process in a simple and summarized manner. Recent papers have used the idea of subsampling to estimate these quantities, providing estimators with superior performance in the case of strong violations of the M...
survidm: An R package for Inference and Prediction in an Illness-Death Model
Soutinho, Gustavo; Sestelo, Marta; Machado, Luís MeiraMulti-state models are a useful way of describing a process in which an individual moves through a number of finite states in continuous time. The illness-death model plays a central role in the theory and practice of these models, describing the dynamics of healthy subjects who may move to an intermediate "diseased" state before entering into a terminal absorbing state. In these models, one important goal is t...
clustcurv: An R Package for Determining Groups in Multiple Curves
Villanueva, Nora,M.; Sestelo, Marta; Machado, Luís Meira; Roca-Pardiñas, JavierIn many situations, it could be interesting to ascertain whether groups of curves can be performed, especially when confronted with a considerable number of curves. This paper introduces an R package, known as clustcurv, for determining clusters of curves with an automatic selection of their number. The package can be used for determining groups in multiple survival curves as well as for multiple regression cur...
Effect of crown-to-implant ratio and crown height space on marginal bone stress...
Ferreira, José; Machado, Luís Meira; Oliveira, José; Ramos, João CarlosCrown-to-implant ratio and crown height space, associated with the use of short implants, have been related with marginal bone loss. However, it is unclear which of the two entities would play the most important role on the bone remodelling process. Using a finite element analysis, the present work aims to help clarifying how those two factors contribute for the stress generation at the marginal bone level. A n...
Sarcopenia and atherosclerotic occlusive disease: how much we know and what we ...
Ferreira, Joana; Carneiro, Alexandre; Cunha, Pedro; Mansilha, Armando; Vila, Isabel; Cunha, Cidália Cristina Ferreira da; Silva, CristinaPurpose/Background: Sarcopenia (decrease of muscle mass and function) has been linked with atherosclerosis [1]. The EWGSOP2 updated consensus, uses low muscle strength as the primary indicator of sarcopenia [2]. It is acknowledged that strength is better than mass for predicting adverse outcomes [2]. Handgrip strength (HGS) is a simple assessment to estimate overall muscular strength [3]. and is associated with...