Repeatability of dietary patterns extracted through multivariate statistical methods: a literature review in methodological issues

In the last few years, the need for processing large amount of data in nutrition science was dramatically arose. This created the need to apply, primarily, advanced analytical research methods that could enable researchers to handle the large amount of information. Dietary pattern analysis is a commonly used approach to enable and incorporate this phenomenon in nutrition research. This article reviews the most common dietary pattern’s assessment statistical methods, evaluating at the same time the up-to-day knowledge regarding the reliability and validity of the retrieved patterns. The review is based on both a-priori (diet scores) and a-posteriori (multivariate statistical analysis) methods. The reports from the existing few studies suggest that the use of both a-priori and a-posteriori pattern analyses in nutrition surveys should be made with consciousness. The suggestion of new statistical techniques for the control of repeatability of dietary patterns is considered essential.     

Estimating mean QALYs in trial-based cost-effectiveness analysis: the importance of controlling for baseline utility

In trial-based cost-effectiveness analysis baseline mean utility values are invariably imbalanced between treatment arms. A patient's baseline utility is likely to be highly correlated with their quality-adjusted life-years (QALYs) over the follow-up period, not least because it typically contributes to the QALY calculation. Therefore, imbalance in baseline utility needs to be accounted for in the estimation of mean differential QALYs, and failure to control for this imbalance can result in a misleading incremental cost-effectiveness ratio. This paper discusses the approaches that have been used in the cost-effectiveness literature to estimate absolute and differential mean QALYs alongside randomised trials, and illustrates the implications of baseline mean utility imbalance for QALY calculation. Using data from a recently conducted trial-based cost-effectiveness study and a micro-simulation exercise, the relative performance of alternative estimators is compared, showing that widely used methods to calculate differential QALYs provide incorrect results in the presence of baseline mean utility imbalance regardless of whether these differences are formally statistically significant. It is demonstrated that multiple regression methods can be usefully applied to generate appropriate estimates of differential mean QALYs and an associated measure of sampling variability, while controlling for differences in baseline mean utility between treatment arms in the trial.     

Measuring people's preferences regarding ageism in health: some methodological issues and some fresh evidence

In this paper, we outline the three main concepts of 'ageism'; health maximisation ageism, productivity ageism, and fair innings ageism. We provide a methodological overview of the existing empirical literature on people's preferences regarding age and classify these studies according to the types of questions that have been asked. We consider some of the methodological issues involved in eliciting preferences regarding ageism and propose using a fixed duration of benefit rather than, as some studies have done, a benefit that lasts for a full lifetime. Informed by this discussion, we present the results from our own empirical study, carried out in the UK, which combines qualitative and quantitative methods to explore the reasons people have for choosing one age over another. In so doing, we are able to consider the extent to which respondents might bring extraneous factors to bear on their responses and/or disregard relevant information (such as that relating to the fixed nature of the benefit). The results suggest that people are broadly in favour of giving priority to younger over older people, based on arguments relating to both productivity ageism and fair innings ageism. However, respondents appear to assume that a benefit would last for a full lifetime (even if they are told to assume a fixed benefit), unless they are asked to consider a 'full-life' benefit first. This particular framing effect has important implications for preference elicitation studies, suggesting that if you want people to answer the question you have in mind, first ask them the question you think they may have in mind.     

Meta-analyses involving cross-over trials: methodological issues

BACKGROUND: Meta-analysis of randomized controlled trials (RCTs) is usually based on trials where patients are randomized individually into two different, parallel, treatment groups. This paper concentrates on RCTs of a different design-two-period, two-treatment cross-over trials. METHODS: The characteristics of these trials are outlined, with detailed examples of methods for analysis for both continuous and binary data. These case studies are then extended into the context of a meta-analysis. The Cochrane Library was surveyed to assess current practice for synthesis. RESULTS: Methods are described for continuous and binary data for use both when the necessary paired data are given and also when they need to be calculated or imputed, and some suggestions are provided to help people wishing to synthesize data from cross-over trials into meta-analyses. The survey suggested that about 8% of the trials in the Cochrane library were cross-over trials and 18% of the reviews referred to such trials, although there was no consistent approach to their inclusion into the reviews. CONCLUSIONS: Methods do exist for including valuable information from two-period, two-treatment cross-over trials into quantitative reviews. However, poor reporting of cross-over trials will often impede attempts to perform a meta-analysis using the available methods.     

Measuring the impact of oral health problems on children's quality of life: conceptual and methodological issues

Children are subject to oral health problems that can impact their own quality of life and that of their families. The need for measurements to assess the impact of oral health on children's quality of life has been emphasized, and questionnaires have been developed or adapted to this specific group. The aim of this study was to describe such instruments (identified in the literature) and discuss their inherent difficulties. Among such instruments, we highlight the Child Oral Health Quality of Life Questionnaire, for children aged 6-7, 8-10, and 11-14, the Child-Oral Impacts on Daily Performances, for children aged 11-12, and the Early Childhood Oral Health Impact Scale for children aged 2-5. Although progress was observed in this area, more research is needed to develop measurements that apply to children in their dynamic health/disease process, encompassing their psychosocial, family, and social context. The use of such instruments should be encouraged in clinical practice and research.     

A cost utility analysis of treatment options for gallstone disease: Methodological issues and results

The techniques of cost utility analysis (CUA) were used to evaluate the treatment of gallstone disease by open and laparoscopic cholecystectomy and by extracorporeal shockwave lithotripsy (ESWL). The application of the techniques in this context raised three methodological questions which are not satisfactorily resolved in the literature. The first is whether an ex ante or ex post perspective is best adopted for the measurement of quality of life (QoL). The second is the method for converting a short term deterioration in QoL followed by full health into QALYs and the reliability of the methods available. The third is the issue of indirect costs which, in the context of a temporary disease state, cannot be easily avoided. The economic evaluation found laparoscopic cholecystectomy to be generally superior than the competitor technologies (entailing lower costs and better outcomes). However, the results were sensitive to assumptions about the perspective for measuring benefits and the inclusion of indirect costs.     

Dietary patterns and breast cancer: a review with focus on methodological issues

Available information on dietary patterns (multiple dietary components operationalized as a single exposure) and cancer is still sparse. This review presents papers published to date that have identified dietary patterns according to all the existing approaches and have assessed their association with breast cancer. Nineteen articles published since 1995 were identified based on studies conducted in various populations across many countries. The majority of them identified a posteriori dietary patterns, mainly using principal component factor analysis. Six studies did not find associations between any of the identified dietary patterns and breast cancer. Nine studies identified one dietary pattern significantly associated with breast cancer, and the remaining four identified two to four dietary patterns related to breast cancer. Although the body of literature has recently increased, a meaningful assessment of the association between dietary patterns and breast cancer still calls for extra effort to refine the statistical techniques and to address the issue of reproducibility of dietary patterns.     

Involving older people in research: methodological issues

The policy imperative to increase public participation in health and social care research, planning and service delivery raises significant questions about optimum approaches, methods and the extent to which this policy can influence change in practice. This paper highlights the key policy literature on user involvement and participatory research methods to establish the context for a partnership research project exploring perceptions of risk in relation to falls from the perspectives of older people, carers, and health and social care professionals. The paper reports the methods used in developing user involvement in the research at a number of levels, including project management, and a consumer panel working alongside the research team and influencing the dissemination in local falls prevention strategies. The authors draw out the issues related to the context and method of involvement, and discuss the impact on research quality and local service development in health and social care.     

Rescaling quality of life values from discrete choice experiments for use as QALYs: a cautionary tale

Background  

Researchers are increasingly investigating the potential for ordinal tasks such as ranking and discrete choice experiments to estimate QALY health state values. However, the assumptions of random utility theory, which underpin the statistical models used to provide these estimates, have received insufficient attention. In particular, the assumptions made about the decisions between living states and the death state are not satisfied, at least for some people. Estimated values are likely to be incorrectly anchored with respect to death (zero) in such circumstances.     

Gustation as a determinant of ingestion: methodological issues

To better characterize the relationship between taste function and dietary intake, measures of taste sensitivity, perceived intensity and preference for sweet (sucrose) and bitter (urea) stimuli were assessed in 35 healthy adults using aqueous and food tastants. Observations were then correlated with the proportions of calories contributed by carbohydrate, protein, fat and foods characterized by subjects as predominantly sweet or bitter on 7-day diet records. No significant association was noted among single measures of taste function and any of the five intake parameters, although taste profiles comprised of multiple taste ratings accounted for approximately a third of the variance in sweet and bitter calorie consumption. Levels of nutrient intake could not be predicted at better than chance levels using taste responses. Taste function plays a subordinate role to other determinants of food and nutrient intake, although taste profiles may facilitate the prediction of preferred tastes of diets.     

Conceptual and methodological issues in epidemiology: An overview

In 2010 a series of workshops on philosophical and methodological issues in epidemiology was held at the University of Cambridge. The papers in this volume arise from those workshops. This paper represents an effort to identify, in broad brush, some of the major conceptual and methodological issues in epidemiology, which form the basis of an emerging focus on the philosophy of epidemiology.     

Two Approaches for Consolidating Results from Genome Scans of Complex Traits: Selection Methods and Scan Statistics

This work has two purposes: (i) empirically selecting levels of significance that maximize the fraction of markers close to a gene (hit rate) when performing linkage analyses of simulated data and (ii) evaluating the utility of a previously reported scan statistic on the same data. Genotype data were simulated from a trait model of seven susceptibility genes. For purpose (i), five statistics were evaluated on all marker loci in fifty replicates; two‐point lod and heterogeneity lod scores maximized over dominance (mlod, mhlod), a multi‐allelic TDT test, an affected sib‐pair test (ASP), and a model‐free test on all sib‐pairs (ALL_SIBS). Within each replicate the fraction of markers (hit rate) significant at specified levels of significance and also (a) within fifty markers of, or (b) on the same chromosome as a major gene was calculated. For purpose (ii), scan statistics of length 15 were calculated for each chromosome and their empirical significance levels estimated on the basis of 500 replicates generated under no linkage. The scan statistic was applied to the mhlod scores from one replicate (Replicate 5). Empirical p‐values for the scan statistic were determined by computing mhlod scores on 500 replicates of simulated null data. For purpose (i), significance levels between 0.001 and 0.01 had the greatest hit rate for all five methods and both criteria. For criterion (a) at the 0.001 level of significance, both mlod and mhlod displayed the highest hit rates, approximately 0.4 for each. For criterion (b), all methods but ALL_SIBS and ASP had hit rates ranging between 0.4 and 0.5. For purpose (ii), the scan statistic proved equally or more powerful than the single‐locus statistic for two of the seven susceptibility genes while the remaining five genes were not detected. © 2001 Wiley‐Liss, Inc.     

The science of sex research: Some methodological considerations

This paper represents a review of substantive theoretical, methodological, and statistical issues relevant to conducting research on human sexual behavior. Guidelines for maintaining rigor and precision in future investigations are also proposed. So as to be able to address issues that pervade all research on human sexual behavior, six topic areas are discussed: theory-related issues, issues involving research design, issues involving subject selection, measurement issues, data-analytic issues, and issues concerned with human-subject protection. The ultimate objective of this paper is to make suggestions aimed at improving the quality of research on human sexual behavior.Invited paper, Conference on Methodology in Sex Research, Washington, D.C., November 8–19, 1977. This investigation was supported in part by a Research Scientist Development Award (KO2-DA00017), Biomedical Research Support Grant from University of California, Los Angeles, and research grant DA1070 from the U.S. Public Health Service. The assistance of Bonnie Barron is gratefully acknowledged.     

The Georgian adolescent health survey: methodological and strategic issues

Summary. Objectives: To conduct a national survey on adolescent health and lifestyles in Georgia and to thus set up a database on adolescent. Methods: A two-stage cluster sample of around 8000–10 000 in-school 15–18 years adolescents are being reached through a random selection of classes in Georgia. The sample has been stratified by age, region, type of school and language. A self-administered questionnaire of 87 questions has been developed and translated into the four main languages used in Georgia. Results: Up to June 2004, the researchers have reached 511 classes (9306 pupils). In total, 8039 questionnaires have been considered valid. The main concerns encountered for this survey are linked with acceptance of the survey, cross-cultural issues, political and strategic problems as well as inadequate physical environmental support. Conclusion: Despite Georgia’s unfavourable economical and political situation, it has been possible to run a national survey on the health of adolescents, according to the usual standards used in the field. This survey should allow for 1) the identification of priorities in the field of health care and health promotion 2) the monitoring of adolescent health in the future.

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Zusammenfassung. Die Gesundheitsbefragung von Jugendlichen in Georgien: methodologische und strategische Fragen Fragestellung: Um eine nationale Studie über Gesundheitszustand und Lebensstils von Jugendlichen in Georgien durchzuführen und dann eine Datenbasis über Jugendliche zu erstellen. Methoden: Ein Kollektiv von insgesamt 8000–10 000 Schülern von 15–18 Jahren wurde aus zuf?llig ausgew?hlten Schulklassen aus ganz Georgien bestimmt. Die Stichprobe wurde bezüglich Alter, Region, Typ der Schule und Sprache untersucht. Ein anonymisierter, selbst auszufüllender Fragebogen mit 87 Fragen, in die vier georgischen Unterrichtssprachen übersetzt, wurde als Arbeitsgrundlage verwendet. Ergebnisse: Bis Juni 2004 konnten 511 (9306 Schüler) der 599 ausgew?hlten Klassen einbezogen werden. Insgesamt k?nnen 8039 Frageb?gen als auswertbar betrachtet werden. Die Hauptprobleme stellten die Akzeptanz der Befragung, transkulturelle Fragen, politische wie strategische Hindernisse sowie die ungünstiges Klima. Schlussfolgerungen: Trotz der ?konomisch und politisch ungünstigen Situation in Georgien war es m?glich, eine nationale Studie über den Gesundheitszustand der Jugendlichen durchzuführen, welche den üblichen Qualit?tsansprüchen gerecht wird. Diese Studie sollte, 1) die Priorit?ten in der Gesundheitsversorgung und –f?rderung zu identifizieren und 2) die künftige Monitoring der Gesundheit der Jugendlichen erlauben.

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Résumé. Enquête sur la santé des adolescents Géorgiens: questions méthodologiques et stratégiques Objectifs: Mener une enquête nationale sur la santé et les styles de vie des adolescents de Géorgie. Créer une banque de données permettant 1) la création de services de soins et d’interventions préventives efficaces; 2) le monitorage de la santé des jeunes. Méthodes: Un échantillon aléatoire en grappe de 8 à 10 000 élèves agés de 15 à 18 ans a été tiré parmi toutes les classes du pays accueillant des élèves de cette tranche d’age. L’échantillon a été stratifié par age, région, type d’école et langue parlée. Un questionnaire auto-administré et anonyme de 87 questions, traduites en quatre langues, a été utilisé. Résultats: Jusqu’en juin 2004, 511 classes (9306 élèves) ont été rencontrées. Le nombre de questionnaires valides est de 8039. Les problèmes principaux rencontrés pour cette étude sont liés à son acceptation, à des problématiques trans-culturelles, à des barrières d’ordre politique et stratégiques, ainsi qu’à un environnement physique peu favorable. Conclusions: En dépit de conditions économiques et politiques très défavorables en Géorgie, il a été possible de mener une recherche nationale sur la santé des adolescents répondants aux critères de qualité habituels. Cette recherche sera utilisée pour sensibiliser les autorités et les professionnels impliqués dans les activités de soins et de prévention destinées à cette classe d’age.