Edward H. Ip

Lifestyle Change and Mobility in Obese Adults with Type 2 Diabetes

BACKGROUND Adults with type 2 diabetes mellitus often have limitations in mobility that increase with age. An intensive lifestyle intervention that produces weight loss and improves fitness could slow the loss of mobility in such patients. METHODS We randomly assigned 5145 overweight or obese adults between the ages of 45 and 74 years with type 2 diabetes to either an intensive lifestyle intervention or a diabetes support-and-education program; 5016 participants contributed data. We used hidden Markov models to characterize disability states and mixed-effects ordinal logistic regression to estimate the probability of functional decline. The primary outcome was self-reported limitation in mobility, with annual assessments for 4 years. RESULTS At year 4, among 2514 adults in the lifestyle-intervention group, 517 (20.6%) had severe disability and 969 (38.5%) had good mobility; the numbers among 2502 participants in the support group were 656 (26.2%) and 798 (31.9%), respectively. The lifestyle-intervention group had a relative reduction of 48% in the risk of loss of mobility, as compared with the support group (odds ratio, 0.52; 95% confidence interval, 0.44 to 0.63; P<0.001). Both weight loss and improved fitness (as assessed on treadmill testing) were significant mediators of this effect (P<0.001 for both variables). Adverse events that were related to the lifestyle intervention included a slightly higher frequency of musculoskeletal symptoms at year 1. CONCLUSIONS Weight loss and improved fitness slowed the decline in mobility in overweight adults with type 2 diabetes. (Funded by the Department of Health and Human Services and others; ClinicalTrials.gov number, NCT00017953.).

Predictors of posttraumatic growth in women with breast cancer

Posttraumatic growth (PTG) is defined as ‘positive psychological change experienced as a result of a struggle with highly challenging life circumstances’. The current study examined change in PTG over 2 years following breast cancer diagnosis and variables associated with PTG over time.

Measuring disability in older adults: The International Classification System of Functioning, Disability and Health (ICF) framework

Background:  Despite the importance of disability to geriatric medicine, no large scale study has validated the activity and participation domains of the International Classification System of Functioning, Disability, and Health (ICF) in older adults. The current project was designed to conduct such as analysis, and then to examine the psychometric properties of a measure that is based on this conceptual structure.

Empirically indistinguishable multidimensional IRT and locally dependent unidimensional item response models

Multidimensionality is a core concept in the measurement and analysis of psychological data. In personality assessment, for example, constructs are mostly theoretically defined as unidimensional, yet responses collected from the real world are almost always determined by multiple factors. Significant research efforts have concentrated on the use of simulated studies to evaluate the robustness of unidimensional item response models when applied to multidimensional data with a dominant dimension. In contrast, in the present paper, I report the result from a theoretical investigation that a multidimensional item response model is empirically indistinguishable from a locally dependent unidimensional model, of which the single dimension represents the actual construct of interest. A practical implication of this result is that multidimensional response data do not automatically require the use of multidimensional models. Circumstances under which the alternative approach of locally dependent unidimensional models may be useful are discussed.

Neuroanatomical target theory as a predictive model for radiation-induced cognitive decline.

Objective: In a retrospective review to assess neuroanatomical targets of radiation-induced cognitive decline, dose volume histogram (DVH) analyses of specific brain regions of interest (ROI) are correlated to neurocognitive performance in 57 primary brain tumor survivors. Methods: Neurocognitive assessment at baseline included Trail Making Tests A/B, a modified Rey-Osterreith Complex Figure, California or Hopkins Verbal Learning Test, Digit Span, and Controlled Oral Word Association. DVH analysis was performed for multiple neuroanatomical targets considered to be involved in cognition. The %v10 (percent of ROI receiving 10 Gy), %v40, and %v60 were calculated for each ROI. Factor analysis was used to estimate global cognition based on a summary of performance on individual cognitive tests. Stepwise regression was used to determine which dose volume predicted performance on global factors and individual neurocognitive tests for each ROI. Results: Regions that predicted global cognitive outcomes at doses <60 Gy included the corpus callosum, left frontal white matter, right temporal lobe, bilateral hippocampi, subventricular zone, and cerebellum. Regions of adult neurogenesis primarily predicted cognition at %v40 except for the right hippocampus which predicted at %v10. Regions that did not predict global cognitive outcomes at any dose include total brain volume, frontal pole, anterior cingulate, right frontal white matter, and the right precentral gyrus. Conclusions: Modeling of radiation-induced cognitive decline using neuroanatomical target theory appears to be feasible. A prospective trial is necessary to validate these data.

General linear models

This chapter presents the general linear model as an extension to the two-sample t-test, analysis of variance (ANOVA), and linear regression. We illustrate the general linear model using two-way ANOVA as a prime example. The underlying principle of ANOVA, which is based on the decomposition of the value of an observed variable into grand mean, group effect and random noise, is emphasized. Further into this chapter, the F test is introduced as a means to test for the strength of group effect. The procedure of F test for identifying a parsimonious set of factors in explaining an outcome of interest is also described.

Testing for Local Dependency in Dichotomous and Polytomous Item Response Models.

Researchers studying item response models are often interested in examining the effects of local dependency on the validity of the resulting conclusion from statistical inference. This paper focuses on the detection of local dependency. We provide a framework for viewing local dependency within dichotomous and polytomous items that are clustered by design, and present a testing procedure that allows researchers to specifically identify individual item pairs that exhibit local dependency, while controlling for false positive rate. Simulation results from the study indicate that the proposed method is effective. In addition, a discussion of its relation to other existing methods is provided.

Social skills and associated psychopathology in children with chromosome 22q11.2 deletion syndrome: implications for interventions

BACKGROUND Although distinctive neuropsychological impairments have been delineated in children with chromosome 22q11 deletion syndrome (22q11DS), social skills and social cognition remain less well-characterised. OBJECTIVE To examine social skills and social cognition and their relationship with neuropsychological function/behaviour and psychiatric diagnoses in children with 22q11DS. METHODS Sixty-six children with 22q11DS and 54 control participants underwent neuropsychological testing and were administered the Diagnostic Analysis of Non-Verbal Accuracy (DANVA) for face and auditory emotion recognition, a measure of social cognition: their parents/guardians were administered the Social Skills Rating System (SSRS) - parent version, Child Behavior Checklist (CBCL) - parent version and the Computerised Diagnostic Interview Schedule for Children (C-DISC). RESULTS The 22q11DS group exhibited significantly lower social skills total score and more problem social behaviours, lower neurocognitive functioning, higher rates of anxiety disorders and more internalising symptoms than the control group. Participants with 22q11DS also exhibited significant deficits in their ability to read facial expressions compared with the control group, but performed no differently than the control participants in the processing of emotions by tone of voice. Within the 22q11DS group, higher social competency was correlated with higher global assessment of functioning and parental socio-economic status. Social competency was worse in those with anxiety disorders, attention deficit hyperactivity disorder, more than two psychiatric diagnoses on the C-DISC and higher internalising symptoms. No significant correlations of SSRS scores were seen with IQ, executive functions, attention, or verbal learning and memory. No correlations were found between social cognition and social skill scores. CONCLUSION Our results indicate that social skills in children with 22q11DS are associated with behaviour/emotional functioning and not with neurocognition. Thus, treating the behaviour or emotional problems such as attention deficit hyperactivity disorder and anxiety disorders may provide a pathway for improving social skills in these children.

Evaluation of the Quality of Life in Adult Cancer Survivors (QLACS) scale for long-term cancer survivors in a sample of breast cancer survivors

BackgroundThis paper evaluates psychometric properties of a recently developed measure focusing on the health-related quality of life (HRQL) of long-term cancer survivors, the Quality of Life in Adult Survivors scale (QLACS), in a sample of breast cancer survivors. This represents an important area of study, given the large number of breast cancer patients surviving many years post diagnosis.MethodsAnalyses are based on an 8-year follow-up of a sample of breast cancer survivors who participated in an earlier study conducted in 1995. Participants were re-contacted in 2003 and those who were reachable and agreed to participate (n = 94) were surveyed using a variety of measures including the QLACS. Additional follow-up surveys were conducted 2 weeks and one year later. Psychometric tests of the QLACS included test-retest reliability, concurrent and retrospective validity, and responsiveness.ResultsThe QLACS domain and summary scores showed good test-retest reliability (all test-retest correlations were above .7) and high internal consistency. The Generic Summary Score showed convergent validity with other measures designed to assess generic HRQL. The Cancer-Specific Summary score exhibited divergent validity with generic HRQL measures, but not a cancer-related specific measure. The QLACS Cancer-Specific Summary Score demonstrated satisfactory predictive validity for factors that were previously shown to be correlated with HRQL. The QLACS generally demonstrated a high level of responsiveness to life changes.ConclusionThe QLACS may serve as a useful measure for assessing HRQL among long-term breast cancer survivors that are not otherwise captured by generic measures or those specifically designed for newly diagnosed patients.

Empirical Bayes and Item-Clustering Effects in a Latent Variable Hierarchical Model: A Case Study From the National Assessment of Educational Progress

Empirical Bayes regression procedures are often used in educational and psychological testing as extensions to latent variables models. The National Assessment of Educational Progress (NAEP) is an important national survey using such procedures. The NAEP applies empirical Bayes methods to models from item response theory to calibrate student responses to questions of varying difficulty. Due partially to the limited computing technology that existed when NAEP was first conceived, NAEP analyses are carried out using a two-stage estimation procedure that ignores uncertainty about some model parameters. Furthermore, the item response theory model that NAEP uses ignores the effect of item clustering created by the design of a test form. Using Markov chain Monte Carlo, we simultaneously estimate all parameters of an expanded model that considers item clustering to investigate the impact of item clustering and ignoring uncertainty about model parameters on an important outcome measure that NAEP report. Ignoring these two effects causes substantial underestimation of standard errors and induces a modest bias in location estimates.