Suchergebnisse

There has been a growing interest regarding generalized classes of distributions in statistical theory and practice because of their flexibility in model formation. Multiple imputation under such distributions that span a broader area in the symmetry–kurtosis plane appears to have the potential of better capturing real incomplete data trends. In this article, we impute continuous univariate data that exhibit varying characteristics under two well‐known distributions, assess the extent to which this procedure works properly, make comparisons with normal imputation models in terms of commonly accepted bias and precision measures, and discuss possible generalizations to the multivariate case and to larger families of distributions.

Longitudinal data analysis for biomedical and behavioral sciencesThis innovative book sets forth and describes methods for the analysis of longitudinaldata, emphasizing applications to problems in the biomedical and behavioral sciences. Reflecting the growing importance and use of longitudinal data across many areas of research, the text is designed to help users of statistics better analyze and understand this type of data

This study examines how acute and chronic stresses associated with functional declines in seniors and their spouses are moderated by their informal and formal support contexts. In the United States, states vary greatly in their support for home and community-based services (HCBS) for seniors with disabilities. This state-to-state variation allowed us to examine mental health effects of living in a society supportive of HCBS for the oldest old, who are at high risk for low or declining functions in daily activities and cognitive abilities. Using a ten-year panel study of a nationally representative sample of the oldest old (>=70 years old) covering the period 1993 to 2002, we conducted mixed-effects logistic regression analysis to incorporate time-varying characteristics of persons and states. As expected, low and declining functions in daily living and cognition constituted significant stressors among seniors and their spouse. Results demonstrated the important role of informal support available from non-spouse family/friends in lowering depression. Living in a state supportive of HCBS was associated with lower depression among seniors experiencing consistently low levels of function or recent functional declines, especially among those without informal support. Our findings were consistent with moderating or buffering models of formal support, suggesting that state HCBS support is effective mainly under conditions of high levels of stressors. Political will is needed to prepare US society to collectively support community-based long-term needs, given the difficulty of preparing ourselves fully for common, but often unexpected, functional declines in later life.

Heterogeneity often exists among behavioral growth trajectories in a study population. In the evaluation of intervention effects for longitudinal randomized trials, it is informative to examine the impact of an intervention on subgroups characterized by different types of growth trajectories. This paper presents an application of growth mixture modeling to an ordinal-scale substance-use behavior outcome from the Aban Aya Youth Project (AAYP), a longitudinal preventive intervention trial targeting health-compromising behaviors among adolescents. Results suggested two classes of adolescent substance use growth trajectories: Class 1 (44.7% of the sample) started at a higher level and had a relatively shallow increase over time; Class 2 had a lower baseline level and a rapid increase over time. The intervention effectively reduced the rapid increase of substance use for the adolescents in the second class.

This study examined grade and sex patterns in real‐time measures of daily mood using Ecological Momentary Assessments via palmtop computers among 8th (N=296) and 10th graders (N=266) for 1 year using a three‐wave longitudinal design. Participants responded to five to seven random prompts/day for 7 consecutive days; when prompted, participants rated eight mood adjectives assessing positive affect (PA) and negative affect (NA). Global depressed mood was also assessed via self‐report questionnaire at every wave. Mixed‐effects regression analyses indicated that PA modestly but significantly declined across Grade 8 to 11, but NA was relatively stable over time. Sex by time interactions showed that boys experienced greater declines in daily mood over time than did girls. In contrast, global depressed mood did not change over time, and girls reported higher depressed mood than boys. Findings suggest that normative mood declines in adolescence may be driven by deteriorations in PA, rather than increases in NA.

Medicaid data contain International Classification of Diseases, Clinical Modification (ICD-9-CM) codes indicating maltreatment, yet there is a little information on how valid these codes are for the purposes of identifying maltreatment from health, as opposed to child welfare, data. This study assessed the validity of Medicaid codes in identifying maltreatment. Participants ( n = 2,136) in the first National Survey of Child and Adolescent Well-Being were linked to their Medicaid claims obtained from 36 states. Caseworker determinations of maltreatment were compared with eight sets of ICD-9-CM codes. Of the 1,921 children identified by caseworkers as being maltreated, 15.2% had any relevant ICD-9-CM code in any of their Medicaid files across 4 years of observation. Maltreated boys and those of African American race had lower odds of displaying a maltreatment code. Using only Medicaid claims to identify maltreated children creates validity problems. Medicaid data linkage with other types of administrative data is required to better identify maltreated children.

This study describes cigarette smoking trajectories, the influence of social smoker self-identification (SSID), and correlates of these trajectories in two cohorts of U.S. young adults: a sample from the Chicago metropolitan area (Social Emotional Contexts of Adolescent and Young Adult Smoking Patterns [SECAP], n = 893) and a national sample (Truth Initiative Young Adult Cohort Study [YA Cohort], n = 1,491). Using latent class growth analyses and growth mixture models, five smoking trajectories were identified in each sample: in SECAP: nonsmoking ( n = 658, 73.7%), declining smoking ( n = 20, 2.2%), moderate/stable smoking ( n = 114, 12.8%), high/stable smoking ( n = 79, 8.9%), and escalating smoking ( n = 22, 2.5%); and in YA Cohort: nonsmoking ( n = 1,215, 81.5%), slowly declining smoking ( n = 52, 3.5%), rapidly declining smoking ( n = 50, 3.4%), stable smoking ( n = 139, 9%), and escalating smoking ( n = 35, 2.4%). SSID was most prevalent in moderate/stable smoking (35.5% SECAP), rapidly declining smoking (25.2% YA Cohort), and nonsmoking. Understanding nuances of how smoking identity is formed and used to limit or facilitate smoking behavior in young adults will allow for more effective interventions to reduce tobacco use.