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Several Covariates (several + covariate)
Selected AbstractsDissecting the heterogeneity of rheumatoid arthritis through linkage analysis of quantitative traitsARTHRITIS & RHEUMATISM, Issue 1 2007Lindsey A. Criswell Objective To dissect the heterogeneity of rheumatoid arthritis (RA) through linkage analysis of quantitative traits, specifically, IgM rheumatoid factor (IgM-RF) and anti,cyclic citrullinated peptide (anti-CCP) autoantibody titers. Methods Subjects, 1,002 RA patients from 491 multiplex families recruited by the North American RA Consortium, were typed for 379 microsatellite markers. Anti-CCP titers were determined based on a second-generation enzyme-linked immunosorbent assay, and IgM-RF levels were quantified by immunonephelometry. We used the Merlin statistical package to perform nonparametric quantitative trait linkage analysis. Results For each of the quantitative traits, evidence of linkage, with logarithm of odds (LOD) scores of >1.0, was found in 9 regions. For both traits, the strongest evidence of linkage was for marker D6S1629 on chromosome 6p (LOD 14.02 for anti-CCP and LOD 12.09 for RF). Six other regions with LOD scores of >1.0 overlapped between the 2 traits, on chromosomes 1p21.1, 5q15, 8p23.1, 16p12.1, 16q23.1, and 18q21.31. Evidence of linkage to anti-CCP titer but not to RF titer was found in 2 regions (chromosomes 9p21.3 and 10q21.1), and evidence of linkage to RF titer but not to anti-CCP titer was found in 2 regions (chromosomes 5p15.2 and 1q42.3). Several covariates were significantly associated with 1 or both traits, and linkage analysis exploring the covariate effects revealed striking effects of sex in modulating linkage signals for several chromosomal regions. For example, sex had a striking impact on the linkage results for both quantitative traits on chromosome 6p (P = 0.0007 for anti-CCP titer and P = 0.0012 for RF titer), suggesting a sex,HLA region interaction. Conclusion Analysis of quantitative components of RA is a promising approach for dissecting the genetic heterogeneity of this complex disorder. These results highlight the potential importance of sex or other covariates that may modulate some of the genetic effects that influence the risk of specific disease manifestations. [source] Modeling mood variation associated with smoking: an application of a heterogeneous mixed-effects model for analysis of ecological momentary assessment (EMA) dataADDICTION, Issue 2 2009Donald Hedeker ABSTRACT Aims Mixed models are used increasingly for analysis of ecological momentary assessment (EMA) data. The variance parameters of the random effects, which indicate the degree of heterogeneity in the population of subjects, are considered usually to be homogeneous across subjects. Modeling these variances can shed light on interesting hypotheses in substance abuse research. Design We describe how these variances can be modeled in terms of covariates to examine the covariate effects on between-subjects variation, focusing on positive and negative mood and the degree to which these moods change as a function of smoking. Setting The data are drawn from an EMA study of adolescent smoking. Participants Participants were 234 adolescents, either in 9th or 10th grades, who provided EMA mood reports from both random prompts and following smoking events. Measurements We focused on two mood outcomes: measures of the subject's negative and positive affect and several covariates: gender, grade, negative mood regulation and smoking level. Findings and conclusions Following smoking, adolescents experienced higher positive affect and lower negative affect than they did at random, non-smoking times. Our analyses also indicated an increased consistency of subjective mood responses as smoking experience increased and a diminishing of mood change. [source] The role of depressive symptoms in recovery from injuries to the extremities in older persons.INTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, Issue 1 2003A prospective study Abstract Background Previous research suggested that depressive symptoms play a role in recovery after hip fracture. However none of these studies were prospective and included only patients with hip fractures. Objective To examine the effect of depressive symptoms on the recovery of (instrumental) activities of daily living after fall-related injuries to the extremities in older persons. Design Prospective cohort study. Methods Data were collected from 168 older persons at baseline, prior to their injuries (hip fractures, other fractures or contortions and dislocations), and 8 weeks, 5 months and 12 months after their accident. Hierarchical multiple regression analysis was used to study the impact of depressive symptoms (as assessed with the Hospital Anxiety and Depression Scale; HADS) on disability (as assessed with the Groningen Activity Restriction Scale; GARS) after the injury while adjusting for several covariates. Results Depressive symptoms at baseline were not predictive for disability after the injury when covariates were taken into account. However, depressive symptoms 8 weeks after the fall were significantly related to disability at 8 weeks, 5 months and even 12 months after the injury. In addition, disability levels before the injury were highly predictive for recovery later on. Severity of injury was particularly predictive for disability at 8 weeks while age (which may generally represent the amount of physiological reserve) predicted disability at 5 and 12 months after the injury. Cognitive functioning 8 weeks post-injury was, in contrast to previous research, not predictive for recovery when covariates were taken into account. Conclusions Pre-injury levels of disability and post-injury depressive symptoms are associated with recovery and may warrant concern and special attention in clinical practice. Copyright © 2002 John Wiley & Sons, Ltd. [source] Ambulatory monitoring and physical health report in Vietnam veterans with and without chronic posttraumatic stress disorderJOURNAL OF TRAUMATIC STRESS, Issue 4 2003Jean C. Beckham Abstract This study investigated the associations among PTSD, ambulatory cardiovascular monitoring, and physical health self-reports in 117 male Vietnam combat veterans (61 with PTSD and 56 without PTSD). PTSD was associated with health symptoms and number of current health conditions beyond the influence of several covariates. PTSD was associated with greater systolic blood pressure variability, and an elevated percentage of heart rate and systolic blood pressure readings above baseline. Higher mean heart rate and an elevated percentage of heart rate above baseline were associated with physical health symptoms. None of the ambulatory monitoring variables mediated the association between PTSD and physical health outcomes. Findings suggest that the interrelationships among ambulatory autonomic responses, PTSD, and physical health deserve more research attention. [source] | ||||||||||