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  1. Article ; Online: Left-censored recurrent event analysis in epidemiological studies

    Gilma Hernández-Herrera / David Moriña / Albert Navarro

    BMC Medical Research Methodology, Vol 22, Iss 1, Pp 1-

    a proposal for when the number of previous episodes is unknown

    2022  Volume 9

    Abstract: Abstract Background When dealing with recurrent events in observational studies it is common to include subjects who became at risk before follow-up. This phenomenon is known as left censoring, and simply ignoring these prior episodes can lead to biased ... ...

    Abstract Abstract Background When dealing with recurrent events in observational studies it is common to include subjects who became at risk before follow-up. This phenomenon is known as left censoring, and simply ignoring these prior episodes can lead to biased and inefficient estimates. We aimed to propose a statistical method that performs well in this setting. Methods Our proposal was based on the use of models with specific baseline hazards. In this, the number of prior episodes were imputed when unknown and stratified according to whether the subject had been at risk of presenting the event before t = 0. A frailty term was also used. Two formulations were used for this “Specific Hazard Frailty Model Imputed” based on the “counting process” and “gap time.” Performance was then examined in different scenarios through a comprehensive simulation study. Results The proposed method performed well even when the percentage of subjects at risk before follow-up was very high. Biases were often below 10% and coverages were around 95%, being somewhat conservative. The gap time approach performed better with constant baseline hazards, whereas the counting process performed better with non-constant baseline hazards. Conclusions The use of common baseline methods is not advised when knowledge of prior episodes experienced by a participant is lacking. The approach in this study performed acceptably in most scenarios in which it was evaluated and should be considered an alternative in this context. It has been made freely available to interested researchers as R package miRecSurv.
    Keywords Medicine (General) ; R5-920
    Subject code 310
    Language English
    Publishing date 2022-01-01T00:00:00Z
    Publisher BMC
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Correction

    David Moriña / Pedro Puig / Albert Navarro

    BMC Medical Research Methodology, Vol 22, Iss 1, Pp 1-

    Analysis of zero inflated dichotomous variables from a Bayesian perspective: application to occupational health

    2022  Volume 1

    Keywords Medicine (General) ; R5-920
    Language English
    Publishing date 2022-08-01T00:00:00Z
    Publisher BMC
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: Analysis of zero inflated dichotomous variables from a Bayesian perspective

    David Moriña / Pedro Puig / Albert Navarro

    BMC Medical Research Methodology, Vol 21, Iss 1, Pp 1-

    application to occupational health

    2021  Volume 9

    Abstract: Abstract Background Zero-inflated models are generally aimed to addressing the problem that arises from having two different sources that generate the zero values observed in a distribution. In practice, this is due to the fact that the population ... ...

    Abstract Abstract Background Zero-inflated models are generally aimed to addressing the problem that arises from having two different sources that generate the zero values observed in a distribution. In practice, this is due to the fact that the population studied actually consists of two subpopulations: one in which the value zero is by default (structural zero) and the other is circumstantial (sample zero). Methods This work proposes a new methodology to fit zero inflated Bernoulli data from a Bayesian approach, able to distinguish between two potential sources of zeros (structural and non-structural). Results The proposed methodology performance has been evaluated through a comprehensive simulation study, and it has been compiled as an R package freely available to the community. Its usage is illustrated by means of a real example from the field of occupational health as the phenomenon of sickness presenteeism, in which it is reasonable to think that some individuals will never be at risk of suffering it because they have not been sick in the period of study (structural zeros). Without separating structural and non-structural zeros one would be studying jointly the general health status and the presenteeism itself, and therefore obtaining potentially biased estimates as the phenomenon is being implicitly underestimated by diluting it into the general health status. Conclusions The proposed methodology is able to distinguish two different sources of zeros (structural and non-structural) from dichotomous data with or without covariates in a Bayesian framework, and has been made available to any interested researcher in the form of the bayesZIB R package ( https://cran.r-project.org/package=bayesZIB ).
    Keywords Presenteeism ; Bayesian methods ; Zero-inflation ; Simulation study ; Bernoulli mixture models ; Medicine (General) ; R5-920
    Subject code 310
    Language English
    Publishing date 2021-12-01T00:00:00Z
    Publisher BMC
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Implementation of web-based respondent driven sampling in epidemiological studies

    Pedro Ferrer-Rosende / María Feijoo-Cid / María Isabel Fernández-Cano / Sergio Salas-Nicás / Valeria Stuardo-Ávila / Albert Navarro-Giné

    BMC Medical Research Methodology, Vol 23, Iss 1, Pp 1-

    2023  Volume 9

    Abstract: Abstract Background Respondent-driven sampling (RDS) is a peer chain-recruitment method for populations without a sampling frame or that are hard-to-reach. Although RDS is usually done face-to-face, the online version (WebRDS) has drawn a lot of ... ...

    Abstract Abstract Background Respondent-driven sampling (RDS) is a peer chain-recruitment method for populations without a sampling frame or that are hard-to-reach. Although RDS is usually done face-to-face, the online version (WebRDS) has drawn a lot of attention as it has many potential benefits, despite this, to date there is no clear framework for its implementation. This article aims to provide guidance for researchers who want to recruit through a WebRDS. Methods Description of the development phase: guidance is provided addressing aspects related to the formative research, the design of the questionnaire, the implementation of the coupon system using a free software and the diffusion plan, using as an example a web-based cross-sectional study conducted in Spain between April and June 2022 describing the working conditions and health status of homecare workers for dependent people. Results The application of the survey: we discuss about the monitoring strategies throughout the recruitment process and potential problems along with proposed solutions. Conclusions Under certain conditions, it is possible to obtain a sample with recruitment performance similar to that of other RDS without the need for monetary incentives and using a free access software, considerably reducing costs and allowing its use to be extended to other research groups.
    Keywords Epidemiologic methods ; Hard-to-reach populations ; Web based sampling ; Respondent-driven sampling ; WebRDS ; Medicine (General) ; R5-920
    Subject code 028
    Language English
    Publishing date 2023-10-01T00:00:00Z
    Publisher BMC
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: The R Package survsim for the Simulation of Simple and Complex Survival Data

    David Moriña / Albert Navarro

    Journal of Statistical Software, Vol 59, Iss 1, Pp 1-

    2014  Volume 20

    Abstract: We present an R package for the simulation of simple and complex survival data. It covers different situations, including recurrent events and multiple events. The main simulation routine allows the user to introduce an arbitrary number of distributions, ...

    Abstract We present an R package for the simulation of simple and complex survival data. It covers different situations, including recurrent events and multiple events. The main simulation routine allows the user to introduce an arbitrary number of distributions, each corresponding to a new event or episode, with its parameters, choosing between the Weibull (and exponential as a particular case), log-logistic and log-normal distributions.
    Keywords Statistics ; HA1-4737 ; Social Sciences ; H
    Language English
    Publishing date 2014-08-01T00:00:00Z
    Publisher University of California, Los Angeles
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article ; Online: Imputación de valores ausentes en salud pública

    Gilma Hernández / David Moriña / Albert Navarro

    Gaceta Sanitaria, Vol 31, Iss 4, Pp 342-

    conceptos generales y aplicación en variables dicotómicas

    2017  Volume 345

    Abstract: Que haya valores ausentes en variables registradas en encuestas de salud es habitual, pero no lo es imputarlos posteriormente cuando se realiza el análisis. Trabajar con datos imputados puede tener ventajas en términos de precisión de los estimadores y ... ...

    Abstract Que haya valores ausentes en variables registradas en encuestas de salud es habitual, pero no lo es imputarlos posteriormente cuando se realiza el análisis. Trabajar con datos imputados puede tener ventajas en términos de precisión de los estimadores y de identificación sin sesgos de la asociación entre variables. Probablemente, el proceso de imputación sigue siendo desconocido para muchos profesionales no estadísticos, que le atribuyen una alta complejidad y quizás un objetivo que no es exactamente el que persigue. Para aclarar estas cuestiones, esta nota pretende ofrecer una visión amena, no exhaustiva, del proceso de imputación, que permita conocer sus bondades para el trabajo de un salubrista. Todo ello en el marco de variables dicotómicas, habituales en salud pública. Para ilustrar los conceptos se usa un ejemplo en el cual se trabaja con datos con valores ausentes, imputados de forma simple y múltiple.
    Keywords Valores ausentes ; Imputación ; Salud pública ; Epidemiología ; Public aspects of medicine ; RA1-1270
    Language English
    Publishing date 2017-07-01T00:00:00Z
    Publisher Elsevier
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  7. Article ; Online: Analyzing recurrent events when the history of previous episodes is unknown or not taken into account

    Albert Navarro / Georgina Casanovas / Sergio Alvarado / David Moriña

    Gaceta Sanitaria, Vol 31, Iss 3, Pp 227-

    proceed with caution

    2017  Volume 234

    Abstract: Objective: Researchers in public health are often interested in examining the effect of several exposures on the incidence of a recurrent event. The aim of the present study is to assess how well the common-baseline hazard models perform to estimate the ... ...

    Abstract Objective: Researchers in public health are often interested in examining the effect of several exposures on the incidence of a recurrent event. The aim of the present study is to assess how well the common-baseline hazard models perform to estimate the effect of multiple exposures on the hazard of presenting an episode of a recurrent event, in presence of event dependence and when the history of prior-episodes is unknown or is not taken into account. Methods: Through a comprehensive simulation study, using specific-baseline hazard models as the reference, we evaluate the performance of common-baseline hazard models by means of several criteria: bias, mean squared error, coverage, confidence intervals mean length and compliance with the assumption of proportional hazards. Results: Results indicate that the bias worsen as event dependence increases, leading to a considerable overestimation of the exposure effect; coverage levels and compliance with the proportional hazards assumption are low or extremely low, worsening with increasing event dependence, effects to be estimated, and sample sizes. Conclusions: Common-baseline hazard models cannot be recommended when we analyse recurrent events in the presence of event dependence. It is important to have access to the history of prior-episodes per subject, it can permit to obtain better estimations of the effects of the exposures Resumen: Objetivo: A menudo los investigadores en salud pública están interesados en examinar el efecto de varias exposiciones en la incidencia de un evento recurrente. El objetivo de este estudio es evaluar el funcionamiento de los modelos de riesgo basal común al estimar el efecto de múltiples exposiciones sobre el riesgo de presentar un episodio de un evento recurrente, cuando existe dependencia del evento y los antecedentes de los episodios por sujeto son desconocidos o bien no se tienen en cuenta. Métodos: Mediante un estudio exhaustivo de simulación, utilizando modelos de riesgo basal específico como referencia, se evalúa el ...
    Keywords Public aspects of medicine ; RA1-1270
    Language English
    Publishing date 2017-05-01T00:00:00Z
    Publisher Elsevier
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  8. Article ; Online: Socio-economic life course and obesity among adults in Florianopolis, southern Brazil

    Katia Jakovljevic Pudla Wagner / João Luiz Bastos / Albert Navarro / Antonio Fernando Boing

    Gaceta Sanitaria, Vol 32, Iss 3, Pp 244-

    2018  Volume 250

    Abstract: Objective: To estimate the association between socio-economic life course and body mass index (BMI), waist circumference (WC) and general and abdominal obesity in adults. Methods: A cross-sectional analysis of a population-based cohort study of 1,222 ... ...

    Abstract Objective: To estimate the association between socio-economic life course and body mass index (BMI), waist circumference (WC) and general and abdominal obesity in adults. Methods: A cross-sectional analysis of a population-based cohort study of 1,222 adults (aged 22–63) from Florianopolis, southern Brazil. The socio-economic life course was analysed using the educational level of participants and their parents. Height, weight and WC were measured by specially trained staff. Linear and logistic regressions were used with adjustment for confounding factors, and data were stratified according to sex. Results: Mean BMI and WC were about 2 kg/m2 (95% CI: −3.3 to −0.7) and 6 cm (95% CI: −9.7 to −2.9) lower in women with a high socio-economic position, while the association was reversed in men with a high socio-economic position, with WC being about 4 cm higher (95% CI: 0.1 to 7.5). In addition, women who had always been in a high socio-economic position were less likely to have abdominal obesity (OR: 0.38; 95% CI: 0.20 to 0.76) while no such association was found in men. Conclusion: Socio-economic life course influences BMI, WC and obesity, with differences between males and females, thereby indicating that public policies that contemplate a socio-economic life course approach can be effective for controlling obesity. Resumen: Objetivo: Estimar la asociación entre trayectoria socioeconómica e índice de masa corporal (IMC), circunferencia de la cintura (CC) y obesidad general y abdominal en adultos. Métodos: Análisis transversal de un estudio de cohortes de base poblacional en 1222 adultos (22-63 años de edad) en Florianópolis, sur de Brasil. La trayectoria socioeconómica fue analizada mediante el nivel educativo de los padres y los propios participantes. La medición de altura, peso y CC fue realizada por personal especialmente entrenado. Se usaron modelos de regresión lineal y logística ajustando factores confusores y estratificando por sexo. Resultados: El promedio de IMC y CC fue de 2 kg/m2 (intervalo de confianza ...
    Keywords Public aspects of medicine ; RA1-1270
    Language English
    Publishing date 2018-05-01T00:00:00Z
    Publisher Elsevier
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  9. Article ; Online: On the interpretation of the atmospheric mechanism transporting the environmental trigger of Kawasaki Disease.

    Joan Ballester / Sílvia Borràs / Roger Curcoll / Albert Navarro-Gallinad / Sofya Pozdniakova / Lidia Cañas / Jane C Burns / Xavier Rodó

    PLoS ONE, Vol 14, Iss 12, p e

    2019  Volume 0226402

    Abstract: Recent advances on the environmental determinants of Kawasaki Disease have pointed to the important role of the atmospheric transport of a still unknown agent potentially triggering the disease. The hypothesis arose from an innovative methodology ... ...

    Abstract Recent advances on the environmental determinants of Kawasaki Disease have pointed to the important role of the atmospheric transport of a still unknown agent potentially triggering the disease. The hypothesis arose from an innovative methodology combining expertise in climate dynamics, the analysis of ocean and atmosphere data, the use of dispersion models and the search for biological agents in air samples. The approach offered a new perspective to reveal the identity of the potential trigger, but at the same time, it increased the level of complexity, which could potentially lead to the misinterpretation of the mechanisms. Some years after it was originally formulated, we here provide a brief clarification on the approach and limits of the methodology in order to prevent an eventual misuse of our research ideas and theory, so that further research can better focus on the knowledge gaps that still remain open.
    Keywords Medicine ; R ; Science ; Q
    Language English
    Publishing date 2019-01-01T00:00:00Z
    Publisher Public Library of Science (PLoS)
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  10. Article ; Online: Socioeconomic status in childhood and obesity in adults

    Katia Jakovljevic Pudla Wagner / João Luiz Dornelles Bastos / Albert Navarro / David Alejandro Gonzalez-Chica / Antonio Fernando Boing

    Revista de Saúde Pública, Vol 52, Iss

    a population-based study

    2018  

    Abstract: ABSTRACT OBJECTIVE To test whether there is an association between socioeconomic status in childhood and measures of body mass index, waist circumference and the presence of overall and abdominal obesity in adult life. METHODS A cross-sectional analysis ... ...

    Abstract ABSTRACT OBJECTIVE To test whether there is an association between socioeconomic status in childhood and measures of body mass index, waist circumference and the presence of overall and abdominal obesity in adult life. METHODS A cross-sectional analysis of a population-based cohort study, including a sample of adults (22–63 years old) living in Florianópolis, Southern Brazil. The socioeconomic status in childhood was analyzed through the education level of the participant’s parents. Height, weight and waist circumference were measured by previously trained interviewers. Linear and logistic regressions with adjustment for confounding factors and stratification of data according to gender were used. RESULTS Of the 1,222 adults evaluated, 20.4% (95%CI 18.1–22.8) presented overall obesity and 24.8% (95%CI 22.4–27.4), abdominal obesity. The body mass index and waist circumference averages among women were, respectively, 1.2 kg/m2 (95%CI -2.3– -0.04) and 2.8 cm (95%CI -5.3– -0.2) lower among those with higher socioeconomic status in childhood. Among men, waist circumference was 3.9 cm (95%CI 1.0–6.8) higher in individuals with higher socioeconomic status in childhood. Regarding obesity, women of higher socioeconomic status in childhood had lower odds of abdominal obesity (OR = 0.56, 95%CI 0.34–0.90), and no such association was observed among men. CONCLUSIONS The socioeconomic status in childhood influences body mass index, waist circumference and obesity in adults, with a difference in the direction of association according to gender. The higher socioeconomic status among men and the lower socioeconomic status among women were associated with higher adiposity indicators.
    Keywords Adulto ; Obesidade ; epidemiologia ; Fatores de Risco ; Fatores Socioeconômicos ; Estudos Transversais ; Public aspects of medicine ; RA1-1270
    Subject code 796
    Language English
    Publishing date 2018-02-01T00:00:00Z
    Publisher Universidade de São Paulo
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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