Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 63
Filtrar
1.
J Clin Oncol ; 42(15): 1799-1809, 2024 May 20.
Artículo en Inglés | MEDLINE | ID: mdl-38640453

RESUMEN

PURPOSE: To compare outcomes after laparoscopic versus open major liver resection (hemihepatectomy) mainly for primary or metastatic cancer. The primary outcome measure was time to functional recovery. Secondary outcomes included morbidity, quality of life (QoL), and for those with cancer, resection margin status and time to adjuvant systemic therapy. PATIENTS AND METHODS: This was a multicenter, randomized controlled, patient-blinded, superiority trial on adult patients undergoing hemihepatectomy. Patients were recruited from 16 hospitals in Europe between November 2013 and December 2018. RESULTS: Of the 352 randomly assigned patients, 332 patients (94.3%) underwent surgery (laparoscopic, n = 166 and open, n = 166) and comprised the analysis population. The median time to functional recovery was 4 days (IQR, 3-5; range, 1-30) for laparoscopic hemihepatectomy versus 5 days (IQR, 4-6; range, 1-33) for open hemihepatectomy (difference, -17.5% [96% CI, -25.6 to -8.4]; P < .001). There was no difference in major complications (laparoscopic 24/166 [14.5%] v open 28/166 [16.9%]; odds ratio [OR], 0.84; P = .58). Regarding QoL, both global health status (difference, 3.2 points; P < .001) and body image (difference, 0.9 points; P < .001) scored significantly higher in the laparoscopic group. For the 281 (84.6%) patients with cancer, R0 resection margin status was similar (laparoscopic 106 [77.9%] v open 122 patients [84.1%], OR, 0.60; P = .14) with a shorter time to adjuvant systemic therapy in the laparoscopic group (46.5 days v 62.8 days, hazard ratio, 2.20; P = .009). CONCLUSION: Among patients undergoing hemihepatectomy, the laparoscopic approach resulted in a shorter time to functional recovery compared with open surgery. In addition, it was associated with a better QoL, and in patients with cancer, a shorter time to adjuvant systemic therapy with no adverse impact on cancer outcomes observed.


Asunto(s)
Hepatectomía , Laparoscopía , Neoplasias Hepáticas , Calidad de Vida , Humanos , Hepatectomía/métodos , Hepatectomía/efectos adversos , Laparoscopía/efectos adversos , Laparoscopía/métodos , Masculino , Femenino , Persona de Mediana Edad , Neoplasias Hepáticas/cirugía , Neoplasias Hepáticas/secundario , Anciano , Complicaciones Posoperatorias/etiología , Complicaciones Posoperatorias/epidemiología , Adulto , Resultado del Tratamiento
2.
Multivariate Behav Res ; 59(2): 206-228, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-37590444

RESUMEN

In a cluster randomized trial clusters of persons, for instance, schools or health centers, are assigned to treatments, and all persons in the same cluster get the same treatment. Although less powerful than individual randomization, cluster randomization is a good alternative if individual randomization is impossible or leads to severe treatment contamination (carry-over). Focusing on cluster randomized trials with a pretest and post-test of a quantitative outcome, this paper shows the equivalence of four methods of analysis: a three-level mixed (multilevel) regression for repeated measures with as levels cluster, person, and time, and allowing for unstructured between-cluster and within-cluster covariance matrices; a two-level mixed regression with as levels cluster and person, using change from baseline as outcome; a two-level mixed regression with as levels cluster and time, using cluster means as data; a one-level analysis of cluster means of change from baseline. Subsequently, similar equivalences are shown between a constrained mixed model and methods using the pretest as covariate. All methods are also compared on a cluster randomized trial on mental health in children. From these equivalences follows a simple method to calculate the sample size for a cluster randomized trial with baseline measurement, which is demonstrated step-by-step.


Asunto(s)
Proyectos de Investigación , Niño , Humanos , Tamaño de la Muestra , Análisis por Conglomerados , Ensayos Clínicos Controlados Aleatorios como Asunto
3.
Am J Clin Nutr ; 117(6): 1063-1085, 2023 06.
Artículo en Inglés | MEDLINE | ID: mdl-37270287

RESUMEN

Designing studies such that they have a high level of power to detect an effect or association of interest is an important tool to improve the quality and reproducibility of findings from such studies. Since resources (research subjects, time, and money) are scarce, it is important to obtain sufficient power with minimum use of such resources. For commonly used randomized trials of the treatment effect on a continuous outcome, designs are presented that minimize the number of subjects or the amount of research budget when aiming for a desired power level. This concerns the optimal allocation of subjects to treatments and, in case of nested designs such as cluster-randomized trials and multicenter trials, also the optimal number of centers versus the number of persons per center. Since such optimal designs require knowledge of parameters of the analysis model that are not known in the design stage, in particular outcome variances, maximin designs are presented. These designs guarantee a prespecified power level for plausible ranges of the unknown parameters and minimize research costs for the worst-case values of these parameters. The focus is on a 2-group parallel design, the AB/BA crossover design, and cluster-randomized and multicenter trials with a continuous outcome. How to calculate sample sizes for maximin designs is illustrated for examples from nutrition. Several computer programs that are helpful in calculating sample sizes for optimal and maximin designs are discussed as well as some results on optimal designs for other types of outcomes.


Asunto(s)
Modelos Estadísticos , Proyectos de Investigación , Humanos , Tamaño de la Muestra , Reproducibilidad de los Resultados , Estudios Cruzados , Análisis por Conglomerados
4.
Psychol Methods ; 28(1): 89-106, 2023 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-34383531

RESUMEN

To prevent mistakes in psychological assessment, the precision of test norms is important. This can be achieved by drawing a large normative sample and using regression-based norming. Based on that norming method, a procedure for sample size planning to make inference on Z-scores and percentile rank scores is proposed. Sampling variance formulas for these norm statistics are derived and used to obtain the optimal design, that is, the optimal predictor distribution, for the normative sample, thereby maximizing precision of estimation. This is done under five regression models with a quantitative and a categorical predictor, differing in whether they allow for interaction and nonlinearity. Efficient robust designs are given in case of uncertainty about the regression model. Furthermore, formulas are provided to compute the normative sample size such that individuals' positions relative to the derived norms can be assessed with prespecified power and precision. (PsycInfo Database Record (c) 2023 APA, all rights reserved).


Asunto(s)
Tamaño de la Muestra , Humanos , Valores de Referencia , Incertidumbre , Encuestas y Cuestionarios
5.
Ear Hear ; 43(6): 1893-1903, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35470813

RESUMEN

OBJECTIVES: Tinnitus is the perception of sound without an external source, affecting quality of life that can cause severe distress in approximately 1 to 3% of the population of people with tinnitus. Randomized controlled trials of cognitive behavioral therapy for tinnitus have demonstrated its effectiveness in improving quality of life, but the effects of their implementation on a large scale in routine practice remains unknown. Therefore, the main purpose of this study was to examine the effects of stepped-care cognitive behavioral therapy for tinnitus delivered in a tertiary audiological center of a regional hospital. Second, we wished to examine predictors of favorable outcome. DESIGN: Four hundred three adults with chronic tinnitus were enrolled in this prospective observational study (at 3 months, N=334, 8 months, N=261; 12 months, N=214). The primary outcome was health-related quality of life as measured by the Health Utilities Index III (HUI-III) at 12 months. Secondary outcomes were self-reported levels of tinnitus-related distress, disability, affective distress and tinnitus-related negative beliefs and fear. Measures were completed pre-intervention at 3 months, 8 months, and 12 months. Multilevel modeling was used to examine effects and their predictors. RESULTS: Younger participants with lower levels of tinnitus distress were more likely to dropout while those with higher tinnitus distress at baseline and quality of life were more likely to receive step 2 of treatment. MLM analyses revealed, with one exception, no relation between any baseline variable and outcome change over time. Most participants' improvement exceeded minimally clinical important difference criteria for quality of life, tinnitus-related handicap, and tinnitus distress. CONCLUSIONS: Results from this large pragmatic study complements those from randomized controlled trials of cognitive behavioral therapy for chronic tinnitus distress and supports its implementation under "real-world" conditions.


Asunto(s)
Terapia Cognitivo-Conductual , Acúfeno , Adulto , Humanos , Terapia Cognitivo-Conductual/métodos , Estudios Prospectivos , Calidad de Vida , Acúfeno/terapia , Acúfeno/psicología , Enfermedad Crónica , Resultado del Tratamiento
6.
Trials ; 23(1): 206, 2022 Mar 09.
Artículo en Inglés | MEDLINE | ID: mdl-35264216

RESUMEN

BACKGROUND: A shift towards parenchymal-sparing liver resections in open and laparoscopic surgery emerged in the last few years. Laparoscopic liver resection is technically feasible and safe, and consensus guidelines acknowledge the laparoscopic approach in the posterosuperior segments. Lesions situated in these segments are considered the most challenging for the laparoscopic approach. The aim of this trial is to compare the postoperative time to functional recovery, complications, oncological safety, quality of life, survival and costs after laparoscopic versus open parenchymal-sparing liver resections in the posterosuperior liver segments within an enhanced recovery setting. METHODS: The ORANGE Segments trial is an international multicentre randomised controlled superiority trial conducted in centres experienced in laparoscopic liver resection. Eligible patients for minor resections in the posterosuperior segments will be randomised in a 1:1 ratio to undergo laparoscopic or open resections in an enhanced recovery setting. Patients and ward personnel are blinded to the treatment allocation until postoperative day 4 using a large abdominal dressing. The primary endpoint is time to functional recovery. Secondary endpoints include intraoperative outcomes, length of stay, resection margin, postoperative complications, 90-day mortality, time to adjuvant chemotherapy initiation, quality of life and overall survival. Laparoscopic liver surgery of the posterosuperior segments is hypothesised to reduce time to functional recovery by 2 days in comparison with open surgery. With a power of 80% and alpha of 0.04 to adjust for interim analysis halfway the trial, a total of 250 patients are required to be randomised. DISCUSSION: The ORANGE Segments trial is the first multicentre international randomised controlled study to compare short- and long-term surgical and oncological outcomes of laparoscopic and open resections in the posterosuperior segments within an enhanced recovery programme. TRIAL REGISTRATION: ClinicalTrials.gov NCT03270917 . Registered on September 1, 2017. Before start of inclusion. PROTOCOL VERSION: version 12, May 9, 2017.


Asunto(s)
Hepatectomía , Laparoscopía , Neoplasias Hepáticas , Hepatectomía/efectos adversos , Hepatectomía/métodos , Humanos , Laparoscopía/efectos adversos , Laparoscopía/métodos , Tiempo de Internación , Neoplasias Hepáticas/cirugía , Estudios Multicéntricos como Asunto , Calidad de Vida , Ensayos Clínicos Controlados Aleatorios como Asunto , Resultado del Tratamiento
7.
J Biopharm Stat ; 32(5): 717-739, 2022 09 03.
Artículo en Inglés | MEDLINE | ID: mdl-35041565

RESUMEN

The literature on dealing with missing covariates in nonrandomized studies advocates the use of sophisticated methods like multiple imputation (MI) and maximum likelihood (ML)-based approaches over simple methods. However, these methods are not necessarily optimal in terms of bias and efficiency of treatment effect estimation in randomized studies, where the covariate of interest (treatment group) is independent of all baseline (pre-randomization) covariates due to randomization. This has been shown in the literature, but only for missingness on a single baseline covariate. Here, we extend the situation to multiple baseline covariates with missingness and evaluate the performance of MI and ML compared with simple alternative methods under various missingness scenarios in RCTs with a quantitative outcome. We first derive asymptotic relative efficiencies of the simple methods under the missing completely at random (MCAR) scenario and then perform a simulation study for non-MCAR scenarios. Finally, a trial on chronic low back pain is used to illustrate the implementation of the methods. The results show that all simple methods give unbiased treatment effect estimation but with increased mean squared residual. It also turns out that mean imputation and the missing-indicator method are most efficient under all covariate missingness scenarios and perform at least as well as MI and LM in each scenario.


Asunto(s)
Proyectos de Investigación , Sesgo , Simulación por Computador , Interpretación Estadística de Datos , Humanos , Ensayos Clínicos Controlados Aleatorios como Asunto
8.
Biom J ; 63(7): 1444-1463, 2021 10.
Artículo en Inglés | MEDLINE | ID: mdl-34247406

RESUMEN

Cluster randomized trials evaluate the effect of a treatment on persons nested within clusters, with clusters being randomly assigned to treatment. The optimal sample size at the cluster and person level depends on the study cost per cluster and per person, and the outcome variance at the cluster and the person level. The variances are unknown in the design stage and can differ between treatment arms. As a solution, this paper presents a Maximin design that maximizes the minimum relative efficiency (relative to the optimal design) over the variance parameter space, for trials with two treatment arms and a quantitative outcome. This maximin relative efficiency design (MMRED) is compared with a published Maximin design which maximizes the minimum efficiency (MMED). Both designs are also compared with the optimal designs for homogeneous costs and variances (balanced design) and heterogeneous costs and homogeneous variances (cost-conscious design), for a range of variances based upon three published trials. Whereas the MMED is balanced under high uncertainty about the treatment-to-control variance ratio, the MMRED then tends towards a balanced budget allocation between arms, leading to an unbalanced sample size allocation if costs are heterogeneous, similar to the cost-conscious design. Further, the MMRED corresponds to an optimal design for an intraclass correlation (ICC) in the lower half of the assumed ICC range (optimistic), whereas the MMED is the optimal design for the maximum ICC within the ICC range (pessimistic). Attention is given to the effect of the Welch-Satterthwaite degrees of freedom for treatment effect testing on the design efficiencies.


Asunto(s)
Modelos Estadísticos , Proyectos de Investigación , Análisis por Conglomerados , Humanos , Ensayos Clínicos Controlados Aleatorios como Asunto , Tamaño de la Muestra , Incertidumbre
9.
BMC Health Serv Res ; 20(1): 907, 2020 Sep 29.
Artículo en Inglés | MEDLINE | ID: mdl-32993737

RESUMEN

BACKGROUND: Community care professionals need to encourage older adults in performing functional activities to maintain independence. However, professionals often perform functional activities on behalf of older adults. To change this, insights into the behavior and barriers of professionals in encouraging activities are required. In the current study, the MAINtAIN questionnaire, which was developed for nursing homes, was adopted. The objective was to create a modified version that is suitable for measuring behavior and barriers of community care professionals in encouraging functional activities of clients in the community care setting. The overall aims were to assess the content validity, construct validity, and internal consistency of the modified version. METHODS: Data was collected by qualitative and quantitative methods in two phases. During phase one, the MAINtAIN was assessed on appropriateness and feasibility by community nurses (N = 7), and the adapted questionnaire was assessed on content validity by research experts (N = 9) and community care professionals (N = 18). During phase two, the psychometric properties of the adapted MAINtAIN-C were assessed in community care professionals (N = 80). Construct validity was evaluated by an Exploratory Factor Analysis (EFA), and internal consistency was determined by calculating Cronbach's alpha coefficients. RESULTS: The formulation, verbs, and wording of the MAINtAIN were adapted; some items were excluded and relevant items were added, resulting in the MAINtAIN-C with two scales, showing good content validity. The Behaviors scale (20 items) measures perceived behavior in encouraging functional activities, expressing good internal consistency (Cronbach's alpha: .92). The Barriers scale measures barriers in encouraging functional activities related to two dimensions: 1) the clients' context (7 items), with good internal consistency (.78); and 2) the professional, social, and organizational contexts (21 items), showing good internal consistency (.83). CONCLUSIONS: The MAINtAIN-C seems promising to assess the behavior and barriers of community care professionals in encouraging functional activities. It can be used to display a possible difference between perceived and actual behavior, to develop strategies for removing barriers in encouraging activities to foster behavioral change. The results also provide guidance for further research in a larger sample to obtain more insight into the psychometric properties.


Asunto(s)
Actividades Cotidianas/psicología , Servicios de Salud Comunitaria/organización & administración , Personal de Salud/psicología , Relaciones Profesional-Paciente , Encuestas y Cuestionarios , Adulto , Anciano , Análisis Factorial , Femenino , Personal de Salud/estadística & datos numéricos , Humanos , Masculino , Persona de Mediana Edad , Psicometría , Reproducibilidad de los Resultados , Adulto Joven
10.
Pharm Stat ; 19(6): 840-860, 2020 11.
Artículo en Inglés | MEDLINE | ID: mdl-32510791

RESUMEN

In this article, we first review the literature on dealing with missing values on a covariate in randomized studies and summarize what has been done and what is lacking to date. We then investigate the situation with a continuous outcome and a missing binary covariate in more details through simulations, comparing the performance of multiple imputation (MI) with various simple alternative methods. This is finally extended to the case of time-to-event outcome. The simulations consider five different missingness scenarios: missing completely at random (MCAR), at random (MAR) with missingness depending only on the treatment, and missing not at random (MNAR) with missingness depending on the covariate itself (MNAR1), missingness depending on both the treatment and covariate (MNAR2), and missingness depending on the treatment, covariate and their interaction (MNAR3). Here, we distinguish two different cases: (1) when the covariate is measured before randomization (best practice), where only MCAR and MNAR1 are plausible, and (2) when it is measured after randomization but before treatment (which sometimes occurs in nonpharmaceutical research), where the other three missingness mechanisms can also occur. The proposed methods are compared based on the treatment effect estimate and its standard error. The simulation results suggest that the patterns of results are very similar for all missingness scenarios in case (1) and also in case (2) except for MNAR3. Furthermore, in each scenario for continuous outcome, there is at least one simple method that performs at least as well as MI, while for time-to-event outcome MI is best.


Asunto(s)
Ensayos Clínicos Controlados Aleatorios como Asunto/estadística & datos numéricos , Proyectos de Investigación/estadística & datos numéricos , Simulación por Computador , Interpretación Estadística de Datos , Humanos , Modelos Estadísticos , Análisis Numérico Asistido por Computador , Resultado del Tratamiento
11.
Adv Life Course Res ; 43: 100323, 2020 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-36726256

RESUMEN

The use of finite mixture modelling (FMM) is becoming increasingly popular for the analysis of longitudinal repeated measures data. FMMs assist in identifying latent classes following similar paths of temporal development. This paper aims to address the confusion experienced by practitioners new to these methods by introducing the various available techniques, which includes an overview of their interrelatedness and applicability. Our focus will be on the commonly used model-based approaches which comprise latent class growth analysis (LCGA), group-based trajectory models (GBTM), and growth mixture modelling (GMM). We discuss criteria for model selection, highlight often encountered challenges and unresolved issues in model fitting, showcase model availability in software, and illustrate a model selection strategy using an applied example.

12.
Stat Med ; 38(10): 1817-1834, 2019 05 10.
Artículo en Inglés | MEDLINE | ID: mdl-30575062

RESUMEN

In multilevel populations, there are two types of population means of an outcome variable ie, the average of all individual outcomes ignoring cluster membership and the average of cluster-specific means. To estimate the first mean, individuals can be sampled directly with simple random sampling or with two-stage sampling (TSS), that is, sampling clusters first, and then individuals within the sampled clusters. When cluster size varies in the population, three TSS schemes can be considered, ie, sampling clusters with probability proportional to cluster size and then sampling the same number of individuals per cluster; sampling clusters with equal probability and then sampling the same percentage of individuals per cluster; and sampling clusters with equal probability and then sampling the same number of individuals per cluster. Unbiased estimation of the average of all individual outcomes is discussed under each sampling scheme assuming cluster size to be informative. Furthermore, the three TSS schemes are compared in terms of efficiency with each other and with simple random sampling under the constraint of a fixed total sample size. The relative efficiency of the sampling schemes is shown to vary across different cluster size distributions. However, sampling clusters with probability proportional to size is the most efficient TSS scheme for many cluster size distributions. Model-based and design-based inference are compared and are shown to give similar results. The results are applied to the distribution of high school size in Italy and the distribution of patient list size for general practices in England.


Asunto(s)
Análisis por Conglomerados , Tamaño de la Muestra , Consumo de Bebidas Alcohólicas/epidemiología , Simulación por Computador , Inglaterra , Medicina General/estadística & datos numéricos , Hospitalización/estadística & datos numéricos , Humanos , Italia/epidemiología , Densidad de Población , Proyectos de Investigación , Instituciones Académicas/estadística & datos numéricos
13.
BMC Geriatr ; 18(1): 276, 2018 11 13.
Artículo en Inglés | MEDLINE | ID: mdl-30424738

RESUMEN

BACKGROUND: According to the principles of Reablement, home care services are meant to be goal-oriented, holistic and person-centred taking into account the capabilities and opportunities of older adults. However, home care services traditionally focus on doing things for older adults rather than with them. To implement Reablement in practice, the 'Stay Active at Home' programme was developed. It is assumed that the programme leads to a reduction in sedentary behaviour in older adults and consequently more cost-effective outcomes in terms of their health and wellbeing. However, this has yet to be proven. METHODS/ DESIGN: A two-group cluster randomised controlled trial with 12 months follow-up will be conducted. Ten nursing teams will be selected, pre-stratified on working area and randomised into an intervention group ('Stay Active at Home') or control group (no training). All nurses of the participating teams are eligible to participate in the study. Older adults and, if applicable, their domestic support workers (DSWs) will be allocated to the intervention or control group as well, based on the allocation of the nursing team. Older adults are eligible to participate, if they: 1) receive homecare services by the selected teams; and 2) are 65 years or older. Older adults will be excluded if they: 1) are terminally ill or bedbound; 2) have serious cognitive or psychological problems; or 3) are unable to communicate in Dutch. DSWs are eligible to participate if they provide services to clients who fulfil the eligibility criteria for older adults. The study consists of an effect evaluation (primary outcome: sedentary behaviour in older adults), an economic evaluation and a process evaluation. Data for the effect and economic evaluation will be collected at baseline and 6 and/or 12 months after baseline using performance-based and self-reported measures. In addition, data from client records will be extracted. A mixed-methods design will be applied for the process evaluation, collecting data of older adults and professionals throughout the study period. DISCUSSION: This study will result in evidence about the effectiveness, cost-effectiveness and feasibility of the 'Stay Active at Home' programme. TRIAL REGISTRATION: ClinicalTrials.gov: NCT03293303 , registered on 20 September 2017.


Asunto(s)
Servicios de Salud Comunitaria/organización & administración , Personal de Salud/educación , Servicios de Atención de Salud a Domicilio/organización & administración , Evaluación de Programas y Proyectos de Salud , Anciano , Actitud del Personal de Salud , Análisis por Conglomerados , Servicios de Salud Comunitaria/economía , Estudios de Factibilidad , Personal de Salud/economía , Servicios de Atención de Salud a Domicilio/economía , Humanos , Vida Independiente/economía , Desarrollo de Programa
14.
Stat Med ; 37(21): 3027-3046, 2018 09 20.
Artículo en Inglés | MEDLINE | ID: mdl-29888393

RESUMEN

Cluster randomized trials evaluate the effect of a treatment on persons nested within clusters, where treatment is randomly assigned to clusters. Current equations for the optimal sample size at the cluster and person level assume that the outcome variances and/or the study costs are known and homogeneous between treatment arms. This paper presents efficient yet robust designs for cluster randomized trials with treatment-dependent costs and treatment-dependent unknown variances, and compares these with 2 practical designs. First, the maximin design (MMD) is derived, which maximizes the minimum efficiency (minimizes the maximum sampling variance) of the treatment effect estimator over a range of treatment-to-control variance ratios. The MMD is then compared with the optimal design for homogeneous variances and costs (balanced design), and with that for homogeneous variances and treatment-dependent costs (cost-considered design). The results show that the balanced design is the MMD if the treatment-to control cost ratio is the same at both design levels (cluster, person) and within the range for the treatment-to-control variance ratio. It still is highly efficient and better than the cost-considered design if the cost ratio is within the range for the squared variance ratio. Outside that range, the cost-considered design is better and highly efficient, but it is not the MMD. An example shows sample size calculation for the MMD, and the computer code (SPSS and R) is provided as supplementary material. The MMD is recommended for trial planning if the study costs are treatment-dependent and homogeneity of variances cannot be assumed.


Asunto(s)
Ensayos Clínicos Controlados Aleatorios como Asunto , Proyectos de Investigación , Análisis por Conglomerados , Humanos , Modelos Estadísticos , Tamaño de la Muestra
16.
Appetite ; 124: 89-98, 2018 05 01.
Artículo en Inglés | MEDLINE | ID: mdl-28479405

RESUMEN

Working Memory (WM) plays a crucial role in successful self-regulation of behavior, including weight regulation. Improving WM might therefore be a promising strategy to support weight loss. In the present study, overweight individuals with a desire to lose weight (N = 91) received an online lifestyle intervention, in conjunction with either 25 sessions of gamified WM training (experimental condition) or a sham training (control). Primary outcomes were Body Mass Index (BMI) and food intake at posttest. Secondary outcomes were executive functioning, self-control, eating style, eating psychopathology and healthy eating. Data were analyzed with mixed regression analyses with condition as between-subjects factor (experimental versus control) and time as within-subjects factor (baseline, posttest, FU1 after one month and FU2 after six months). Results revealed that the experimental condition increased their WM span more than control from pretest to posttest, and these gains were retained at FU1, though lost at FU2. No transfer effects of WM training to other executive functioning measures were found. During the bogus taste test at posttest, participants in the experimental condition consumed significantly less than participants in the control condition. However, both conditions showed a small reduction in BMI, improved eating style, reduced eating disorder pathology, and reported more self-control and a healthier eating pattern. In conclusion, the current results provide some evidence that WM training can improve eating behavior at the short term. However, the WM gains were short-lived, and the added value of WM training as an intervention to promote weight loss could not be established. Future studies should test the added value of WM training booster sessions to promote weight loss over a prolonged period of time.


Asunto(s)
Peso Corporal , Memoria a Corto Plazo , Sobrepeso/terapia , Juegos de Video , Adolescente , Adulto , Índice de Masa Corporal , Ingestión de Alimentos/psicología , Función Ejecutiva , Femenino , Estudios de Seguimiento , Conductas Relacionadas con la Salud , Educación en Salud , Humanos , Estilo de Vida , Masculino , Persona de Mediana Edad , Obesidad/terapia , Sobrepeso/psicología , Autocontrol/psicología , Encuestas y Cuestionarios , Resultado del Tratamiento , Adulto Joven
17.
Stat Med ; 37(1): 12-27, 2018 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-28948651

RESUMEN

At the design stage of a study, it is crucial to compute the sample size needed for treatment effect estimation with maximum precision and power. The optimal design depends on the costs, which may be known at the design stage, and on the outcome variances, which are unknown. A balanced design, optimal for homogeneous costs and variances, is typically used. An alternative to the balanced design is a design optimal for the known and possibly heterogeneous costs, and homogeneous variances, called costs considering design. Both designs suffer from loss of efficiency, compared with optimal designs for heterogeneous costs and variances. For 2 × 2 multicenter trials, we compute the relative efficiency of the balanced and the costs considering designs, relative to the optimal designs. We consider 2 heterogeneous costs and variance scenarios (in 1 scenario, 2 treatment conditions have small and 2 have large costs and variances; in the other scenario, 1 treatment condition has small, 2 have intermediate, and 1 has large costs and variances). Within these scenarios, we examine the relative efficiency of the balanced design and of the costs considering design as a function of the extents of heterogeneity of the costs and of the variances and of their congruence (congruent when the cheapest treatment has the smallest variance, incongruent when the cheapest treatment has the largest variance). We find that the costs considering design is generally more efficient than the balanced design, and we illustrate this theory on a 2 × 2 multicenter trial on lifestyle improvement of patients in general practices.


Asunto(s)
Ensayos Clínicos como Asunto/métodos , Bioestadística , Ensayos Clínicos como Asunto/economía , Ensayos Clínicos como Asunto/estadística & datos numéricos , Medicina General , Costos de la Atención en Salud , Promoción de la Salud , Humanos , Estilo de Vida , Modelos Lineales , Modelos Estadísticos , Estudios Multicéntricos como Asunto/estadística & datos numéricos , Ensayos Clínicos Controlados Aleatorios como Asunto/estadística & datos numéricos , Tamaño de la Muestra , Resultado del Tratamiento
18.
Stat Med ; 35(24): 4320-4334, 2016 10 30.
Artículo en Inglés | MEDLINE | ID: mdl-27271007

RESUMEN

Typically, clusters and individuals in cluster randomized trials are allocated across treatment conditions in a balanced fashion. This is optimal under homogeneous costs and outcome variances. However, both the costs and the variances may be heterogeneous. Then, an unbalanced allocation is more efficient but impractical as the outcome variance is unknown in the design stage of a study. A practical alternative to the balanced design could be a design optimal for known and possibly heterogeneous costs and homogeneous variances. However, when costs and variances are heterogeneous, both designs suffer from loss of efficiency, compared with the optimal design. Focusing on cluster randomized trials with a 2 × 2 design, the relative efficiency of the balanced design and of the design optimal for heterogeneous costs and homogeneous variances is evaluated, relative to the optimal design. We consider two heterogeneous scenarios (two treatment arms with small, and two with large, costs or variances, or one small, two intermediate, and one large costs or variances) at each design level (cluster, individual, and both). Within these scenarios, we compute the relative efficiency of the two designs as a function of the extents of heterogeneity of the costs and variances, and the congruence (the cheapest treatment has the smallest variance) and incongruence (the cheapest treatment has the largest variance) between costs and variances. We find that the design optimal for heterogeneous costs and homogeneous variances is generally more efficient than the balanced design and we illustrate this theory on a trial that examines methods to reduce radiological referrals from general practices. Copyright © 2016 John Wiley & Sons, Ltd.


Asunto(s)
Interpretación Estadística de Datos , Modelos Estadísticos , Ensayos Clínicos Controlados Aleatorios como Asunto , Análisis por Conglomerados , Humanos , Tamaño de la Muestra
19.
Stat Med ; 35(12): 2000-15, 2016 05 30.
Artículo en Inglés | MEDLINE | ID: mdl-26756696

RESUMEN

In two-armed trials with clustered observations the arms may differ in terms of (i) the intraclass correlation, (ii) the outcome variance, (iii) the average cluster size, and (iv) the number of clusters. For a linear mixed model analysis of the treatment effect, this paper examines the expected efficiency loss due to varying cluster sizes based upon the asymptotic relative efficiency of varying versus constant cluster sizes. Simple, but nearly cost-optimal, correction factors are derived for the numbers of clusters to repair this efficiency loss. In an extensive Monte Carlo simulation, the accuracy of the asymptotic relative efficiency and its Taylor approximation are examined for small sample sizes. Practical guidelines are derived to correct the numbers of clusters calculated under constant cluster sizes (within each treatment) when planning a study. Because of the variety of simulation conditions, these guidelines can be considered conservative but safe in many realistic situations. Copyright © 2016 John Wiley & Sons, Ltd.


Asunto(s)
Análisis por Conglomerados , Ensayos Clínicos Controlados Aleatorios como Asunto/métodos , Interpretación Estadística de Datos , Humanos , Modelos Lineales , Modelos Estadísticos , Método de Montecarlo , Ensayos Clínicos Controlados Aleatorios como Asunto/estadística & datos numéricos , Tamaño de la Muestra , Estadística como Asunto , Resultado del Tratamiento
20.
Body Image ; 15: 81-9, 2015 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-26280376

RESUMEN

This study tested Expand Your Horizon, a programme designed to improve body image by training women to focus on the functionality of their body using structured writing assignments. Eighty-one women (Mage=22.77) with a negative body image were randomised to the Expand Your Horizon programme or to an active control programme. Appearance satisfaction, functionality satisfaction, body appreciation, and self-objectification were measured at pretest, posttest, and one-week follow-up. Following the intervention, participants in the Expand Your Horizon programme experienced greater appearance satisfaction, functionality satisfaction, and body appreciation, and lower levels of self-objectification, compared to participants in the control programme. Partial eta-squared effect sizes were of small to medium magnitude. This study is the first to show that focusing on body functionality can improve body image and reduce self-objectification in women with a negative body image. These findings provide support for addressing body functionality in programmes designed to improve body image.


Asunto(s)
Imagen Corporal/psicología , Satisfacción Personal , Evaluación de Programas y Proyectos de Salud , Autoimagen , Adolescente , Adulto , Femenino , Humanos , Encuestas y Cuestionarios , Adulto Joven
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA