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Longitudinal Trajectories (longitudinal + trajectory)
Selected AbstractsLongitudinal Trajectories of Ethnic Identity During the College YearsJOURNAL OF RESEARCH ON ADOLESCENCE, Issue 4 2009Moin Syed The goals of this study were to examine trajectories of change in ethnic identity during the college years and to explore group-level and individual-level variations. Participants were 175 diverse college students who completed indices of ethnic identity exploration and commitment, self-esteem, and domain-general identity resolution. Multilevel modeling analyses indicated that exploration and commitment continued to increase during the college years. Although there were ethnic differences in initial levels of ethnic identity, the rate of change did not vary by ethnicity. Domain-general identity was positively associated with exploration and commitment and mediated the association between self-esteem and commitment. The findings highlight the ongoing development of ethnic identity beyond adolescence and suggest that ethnic identity is part of the larger identity project. [source] Time-Varying Functional Regression for Predicting Remaining Lifetime Distributions from Longitudinal TrajectoriesBIOMETRICS, Issue 4 2005Hans-Georg Müller Summary A recurring objective in longitudinal studies on aging and longevity has been the investigation of the relationship between age-at-death and current values of a longitudinal covariate trajectory that quantifies reproductive or other behavioral activity. We propose a novel technique for predicting age-at-death distributions for situations where an entire covariate history is included in the predictor. The predictor trajectories up to current time are represented by time-varying functional principal component scores, which are continuously updated as time progresses and are considered to be time-varying predictor variables that are entered into a class of time-varying functional regression models that we propose. We demonstrate for biodemographic data how these methods can be applied to obtain predictions for age-at-death and estimates of remaining lifetime distributions, including estimates of quantiles and of prediction intervals for remaining lifetime. Estimates and predictions are obtained for individual subjects, based on their observed behavioral trajectories, and include a dimension-reduction step that is implemented by projecting on a single index. The proposed techniques are illustrated with data on longitudinal daily egg-laying for female medflies, predicting remaining lifetime and age-at-death distributions from individual event histories observed up to current time. [source] Use of longitudinal data in genetic studies in the genome-wide association studies era: summary of Group 14GENETIC EPIDEMIOLOGY, Issue S1 2009Berit Kerner Abstract Participants analyzed actual and simulated longitudinal data from the Framingham Heart Study for various metabolic and cardiovascular traits. The genetic information incorporated into these investigations ranged from selected single-nucleotide polymorphisms to genome-wide association arrays. Genotypes were incorporated using a broad range of methodological approaches including conditional logistic regression, linear mixed models, generalized estimating equations, linear growth curve estimation, growth modeling, growth mixture modeling, population attributable risk fraction based on survival functions under the proportional hazards models, and multivariate adaptive splines for the analysis of longitudinal data. The specific scientific questions addressed by these different approaches also varied, ranging from a more precise definition of the phenotype, bias reduction in control selection, estimation of effect sizes and genotype associated risk, to direct incorporation of genetic data into longitudinal modeling approaches and the exploration of population heterogeneity with regard to longitudinal trajectories. The group reached several overall conclusions: (1) The additional information provided by longitudinal data may be useful in genetic analyses. (2) The precision of the phenotype definition as well as control selection in nested designs may be improved, especially if traits demonstrate a trend over time or have strong age-of-onset effects. (3) Analyzing genetic data stratified for high-risk subgroups defined by a unique development over time could be useful for the detection of rare mutations in common multifactorial diseases. (4) Estimation of the population impact of genomic risk variants could be more precise. The challenges and computational complexity demanded by genome-wide single-nucleotide polymorphism data were also discussed. Genet. Epidemiol. 33 (Suppl. 1):S93,S98, 2009. © 2009 Wiley-Liss, Inc. [source] Integrating Person-Centered and Variable-Centered Approaches in the Study of Developmental Courses and Transitions in Alcohol Use: Introduction to the Special SectionALCOHOLISM, Issue 6 2000Marsha E. Bates This special section consists of research from the symposium "Integrating Person-Centered and Variable-Centered Approaches to the Study of Developmental Courses and Transitions in Alcohol Use," presented at the 1999 Annual Meeting of the Research Society on Alcoholism. The section focuses on ways to integrate variable-centered and person-centered approaches to better understand longitudinal trajectories of alcohol use and associated problems. Our aim is to increase awareness and discussion of alternative conceptual and quantitative approaches that involve both a person-centered and a variable-centered component, and to make these methods more accessible to alcohol and other drug researchers. The first paper provides a general latent variable modeling framework within which to conceptualize developmental questions that involve the combination of continuous latent variables and categorical variables that represent classifications of individuals into meaningful subgroups. This is followed by three empirical papers that use integrative methods to examine early adult outcomes of adolescent binge drinking; potential mediators of familial alcoholism effects on alcohol and tobacco use disorder comorbidity; and the ability of psychopathology, substance use, and parental history of alcohol problems to predict individual differences in the likelihood of transitions in drinking behavior during adolescence. The section concludes with a discussion of the statistical basis for integrating person-centered and variable-centered methods, a comparison of study findings, and directions for future research. [source] Relationship between health services outcomes and social and economic outcomes in workplace injury and disease: Data sources and methods,AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 3 2001Cam Mustard ScD Abstract Background Understanding the mediating role of health care in mitigating social, economic and occupational role disability is a complex task. Methods No single method of research will be successful in addressing all elements of this NORA research priority area. In this paper, we argue that research methods are needed which have the following components: (1) the detailed measurement of therapeutic intervention and the impacts of this intervention on clinical and functional health status using study designs which rule out competing explanations, (2) a longitudinal follow-up component which measures social, economic, and occupational role function following the conclusion of therapy, and (3) a commitment to execute studies across multiple settings to observe the variations in health care and in social and occupational role function that arise as a result of differences in labor market factors and employer and government policies. Conclusions More comprehensive portraits of the longitudinal trajectory of individual workers, social, economic and occupational role function following an occupational injury or illness will have significance for a large number of policy sectors. Am. J. Ind. Med. 40:335,343, 2001. © 2001 Wiley-Liss, Inc. 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