Comunidades de práctica predoctorales: Diez años del Seminari Predoc en la Facultat de Ciències Matemàtiques

[EN] The Seminari Predoc is a community of practice organised by PhD students together with the Faculty of Mathematical Sciences of the Valencia University. The aim of these seminars is to help participants to refine and improve their academic presentations, which in turn yields a connecting between them and members from different institutions around the globe as well as with the faculty itself. In this paper, we describe its origin, objectives, and evolution on the occasion of its 10th anniversary.[ES] El Seminari Predoc es una comunidad de práctica organizada por los estudiantes de doctorado vinculados a la Facultat de Ciències Matemàtiques de la Universitat de València que permite dar a conocer su trabajo a toda la comunidad educativa. Este seminario tiene el objetivo de ayudar a los participantes a perfilar y mejorar sus ponencias de carácter académico, estrechando y creando, a su vez, vínculos con otras personas en una situación similar, con los diferentes miembros de la Facultad y con los estudiantes visitantes. En este artículo describimos su origen, objetivos y evolución aprovechando su décimo aniversario.Calvo Bayarri, G.; Castillo Medina, J.; Cosme Llópez, E.; Dantas, S.; Giménez Conejero, R.; Martínez Minaya, J.; Reula Martín, M. (2022). Comunidades de práctica predoctorales: Diez años del Seminari Predoc en la Facultat de Ciències Matemàtiques. Editorial Universitat Politècnica de València. 1-14. https://doi.org/10.4995/INRED2022.2022.1580511

Bayesian hierarchical modelling for repeated measures and longitudinal data

This memory goes further into the methodological development of models for repeated measures data and longitudinal data within the framework of Bayesian hierarchical modelling. The models under investigation essentially comprise four components: the response variable, a potential hidden or latent process, the set of parameters and hyperparameters, and the set of random effects and serial correlation terms. The inherent complexity of repeated measures and longitudinal data lies in their often multivariate nature, providing us with information not only about the overall population but also about each individual. Additionally, this type of data frequently arises in various fields of knowledge, such as medicine, public health, education, economics, psychology, biology, fisheries, and sports, among others. Therefore, they can play a key role in different branches of learning. In our research, we cover a wide variety of data from different fields, each explored in a separate chapter. Chapter 2 is dedicated to a medical research involving 198 patients. This chapter investigates the intricate connection between intra-abdominal pressure during laparoscopic surgery and the resulting intra-abdominal volume. Meanwhile, Chapter 3 shifts its focus towards a fisheries analysis, specifically on the European sardine industry in the Mediterranean Sea, dividing the data by country. Furthermore, our exploration delves into the realm of sports analysis in Chapters 5 and 6. These chapters enter into the professional basketball and wheelchair basketball domains, respectively. The sports domain provides an abundant source of longitudinal data, brimming with untapped potential for precise longitudinal analysis. The research is primarily motivated by the numerous real-world challenges generated by studies involving longitudinal data and repeated measurements. This work yields both practical insights and methodological advancements. On the practical front, we highlight three key points. Chapter 2 sheds light on the critical role of gender and age in the optimal intra-abdominal space of patients undergoing laparoscopy. In Chapter 3, there is evidence of a concerning decline in the European Sardine catch in artisanal and industrial fishing in the Mediterranean over the past three decades. Furthermore, a positive linear relationship between these two types of fishing is revealed in each country. Finally, Chapter 5 uncovers something akin to a ”cold hand” phenomenon during the 2005-2006 season of the Miami Heat NBA basketball team. However, beyond these practical findings, this research contains methodological statistical contributions in essentially four aspects. In Chapter 3, a novel joint longitudinal model is developed, establishing a linear relationship between the random effects associated with the same individual in different response variables. Chapter 4 introduces a methodology for comparing longitudinal models with random effects and serial correlation terms, calculating their marginal likelihood through the power posterior method. Chapter 5 demonstrates the ability of Bayesian longitudinal models with hidden Markov chain structure to describe the hot hand phenomenon in basketball performance through a latent Markov chain with two states, cold and hot. Finally, Chapter 6 innovatively integrates Bayesian longitudinal modelling techniques and integer linear optimisation. These two techniques are used to analyse players’ temporal performance data and identify optimal line-up configurations to maximise overall performance, respectively. This way, we obtain a probability distribution for the solution of an integer linear optimisation problem

Initial invasive or conservative strategy for stable coronary disease

BACKGROUND Among patients with stable coronary disease and moderate or severe ischemia, whether clinical outcomes are better in those who receive an invasive intervention plus medical therapy than in those who receive medical therapy alone is uncertain. METHODS We randomly assigned 5179 patients with moderate or severe ischemia to an initial invasive strategy (angiography and revascularization when feasible) and medical therapy or to an initial conservative strategy of medical therapy alone and angiography if medical therapy failed. The primary outcome was a composite of death from cardiovascular causes, myocardial infarction, or hospitalization for unstable angina, heart failure, or resuscitated cardiac arrest. A key secondary outcome was death from cardiovascular causes or myocardial infarction. RESULTS Over a median of 3.2 years, 318 primary outcome events occurred in the invasive-strategy group and 352 occurred in the conservative-strategy group. At 6 months, the cumulative event rate was 5.3% in the invasive-strategy group and 3.4% in the conservative-strategy group (difference, 1.9 percentage points; 95% confidence interval [CI], 0.8 to 3.0); at 5 years, the cumulative event rate was 16.4% and 18.2%, respectively (difference, 121.8 percentage points; 95% CI, 124.7 to 1.0). Results were similar with respect to the key secondary outcome. The incidence of the primary outcome was sensitive to the definition of myocardial infarction; a secondary analysis yielded more procedural myocardial infarctions of uncertain clinical importance. There were 145 deaths in the invasive-strategy group and 144 deaths in the conservative-strategy group (hazard ratio, 1.05; 95% CI, 0.83 to 1.32). CONCLUSIONS Among patients with stable coronary disease and moderate or severe ischemia, we did not find evidence that an initial invasive strategy, as compared with an initial conservative strategy, reduced the risk of ischemic cardiovascular events or death from any cause over a median of 3.2 years. The trial findings were sensitive to the definition of myocardial infarction that was used

Health-status outcomes with invasive or conservative care in coronary disease

BACKGROUND In the ISCHEMIA trial, an invasive strategy with angiographic assessment and revascularization did not reduce clinical events among patients with stable ischemic heart disease and moderate or severe ischemia. A secondary objective of the trial was to assess angina-related health status among these patients. METHODS We assessed angina-related symptoms, function, and quality of life with the Seattle Angina Questionnaire (SAQ) at randomization, at months 1.5, 3, and 6, and every 6 months thereafter in participants who had been randomly assigned to an invasive treatment strategy (2295 participants) or a conservative strategy (2322). Mixed-effects cumulative probability models within a Bayesian framework were used to estimate differences between the treatment groups. The primary outcome of this health-status analysis was the SAQ summary score (scores range from 0 to 100, with higher scores indicating better health status). All analyses were performed in the overall population and according to baseline angina frequency. RESULTS At baseline, 35% of patients reported having no angina in the previous month. SAQ summary scores increased in both treatment groups, with increases at 3, 12, and 36 months that were 4.1 points (95% credible interval, 3.2 to 5.0), 4.2 points (95% credible interval, 3.3 to 5.1), and 2.9 points (95% credible interval, 2.2 to 3.7) higher with the invasive strategy than with the conservative strategy. Differences were larger among participants who had more frequent angina at baseline (8.5 vs. 0.1 points at 3 months and 5.3 vs. 1.2 points at 36 months among participants with daily or weekly angina as compared with no angina). CONCLUSIONS In the overall trial population with moderate or severe ischemia, which included 35% of participants without angina at baseline, patients randomly assigned to the invasive strategy had greater improvement in angina-related health status than those assigned to the conservative strategy. The modest mean differences favoring the invasive strategy in the overall group reflected minimal differences among asymptomatic patients and larger differences among patients who had had angina at baseline