Quantum changes in self-efficacy and condom-use intention among youth: A chained cusp catastrophe model.

INTRODUCTION: The complex relationships among HIV knowledge, condom-use skills, self-efficacy, peer influence and intention to use condoms have been rigorously investigated. However, studies guided by a linear behavior change model often explain only a limited amount of variances. This study aims to advance our understanding of the relationships through a nonlinear quantum change paradigm. METHODS: Data (n = 1970, 40.61% male, mean age 16.94 ±â€¯0.74) from a behavioral intervention program among high school students in the Bahamas were analyzed with a chained cusp catastrophe model in two steps. In the first step, self-efficacy was analyzed as the outcome with HIV knowledge/condom-use skills as asymmetry variables and peer influence as bifurcation variable. In the second step, condom-use intention was analyzed as the outcome while self-efficacy (outcome in the first step) was used as bifurcation variable allowing peer influence as bifurcation, and HIV knowledge/condom-use skills were included as asymmetry. Cusp modeling analysis was conducted along with equivalent linear models. RESULTS: The cusp model performed better than the linear and logistic models. Cusp modeling analyses revealed that peer influence significantly bifurcated the relationships between HIV knowledge/condom-use skills and self-efficacy; while both self-efficacy and peer influence significantly bifurcated the relationship between HIV knowledge/condom-use skills and condom-use intention. CONCLUSION: Our findings support the central role of self-efficacy and peer influence as two chains in bridging the complex quantum relationships between HIV knowledge/condom-use skills and condom-use intention among adolescents. The nonlinear cusp catastrophe modeling provided a new method to advance HIV behavioral research.

Linking cognition and frailty in middle and old age: metabolic syndrome matters.

OBJECTIVES: This study examined whether metabolic syndrome (MetS) would moderate the association of cognition with frailty in middle and old age. METHODS: A cross-sectional design was used. Six hundred and ninety participants (age ≥ 50 years) from an on-going national survey were included in the study. Confirmatory factor analysis was applied to determine latent variables of executive function (EF), episodic memory (EM), and MetS based on relevant measurements. Frailty was defined using a modified form of Fried's criteria. RESULTS: Applying structural equation modeling, having MetS significantly increased the likelihood of being frail. Better performance on EM tasks, but not EF, was significantly associated with lower likelihood of MetS. Worse performance on EF, but not EM, significantly increased the likelihood of being frail. There was a significant interacting effect between MetS and EF, but not EM, on frailty. Further contrast analysis indicated that having MetS strengthened the negative association between EF and frailty. CONCLUSION: Metabolic syndrome moderates the relationship between EF and frailty. A prospecitve study is needed to validate such relationships before developing interventions targeting the prevention or treatment of EF and frailty in individuals with MetS.

Self-management intervention for long-term indwelling urinary catheter users: randomized clinical trial.

BACKGROUND: People using long-term indwelling urinary catheters experience multiple recurrent catheter problems. Self-management approaches are needed to avoid catheter-related problems. OBJECTIVES: The aim was to determine effectiveness of a self-management intervention in prevention of adverse outcomes (catheter-related urinary tract infection, blockage, and accidental dislodgement). Healthcare treatment associated with the adverse outcomes and catheter-related quality of life was also studied. METHODS: A randomized clinical trial was conducted. The intervention involved learning catheter-related self-monitoring and self-management skills during home visits by a study nurse (twice during the first month and at 4 months-with a phone call at 2 months). The control group received usual care. Data were collected during an initial face-to-face home interview followed by bimonthly phone interviews. A total of 202 adult long-term urinary catheter users participated. Participants were randomized to treatment or control groups following collection of baseline data. Generalized estimating equations were used for the analysis of treatment effect. RESULTS: In the intervention group, there was a significant decrease in reported blockage in the first 6 months (p = .02), but the effect did not persist. There were no significant effects for catheter-related urinary tract infection or dislodgment. Comparison of baseline rates of adverse outcomes with subsequent periods suggested that both groups improved over 12 months. DISCUSSION: A simple-to-use catheter problems calendar and the bimonthly interviews might have functioned as a modest self-monitoring intervention for persons in both groups. A simplified intervention using a self-monitoring calendar is suggested-with optimal and consistent fluid intake likely to add value.

Evaluation of objective and perceived mental fatigability in older adults with vascular risk.

OBJECTIVES: Mental fatigability refers to the failure to sustain participation in tasks requiring mental effort. Older adults with vascular risk are at particular risk for experiencing mental fatigability. The present study (1) tested a new way of measuring objective mental fatigability by examining its association with perceived mental fatigability; and (2) identified associated psychological, physiological, and situational predictors. METHODS: A cross-sectional study was conducted with 49 community-dwelling participants aged 75+ years with vascular risk. A 20-minute fatigability-manipulation task was used to induce mental fatigability and develop objective and perceived mental fatigability measures. Objective fatigability was calculated by the change of reaction time over the course of the task. Perceived fatigability was calculated by the change of fatigue self-reported before and after the task. A set of potential psychological, physiological, and situational predictors were measured. RESULTS: There was a significant increase in reaction time and self-reported fatigue to the fatigability manipulation task, indicating occurrence of objective and perceived mental fatigability. Reaction time and self-reported fatigue were moderately, but significantly correlated. Higher levels of executive control and having a history of more frequently engaging in mental activities were associated with lower objective mental fatigability. None of the examined factors were associated with perceived mental fatigability. CONCLUSION: Objective and perceived mental fatigability were sensitive to our fatigability-manipulation task. While these two measures were correlated, they were not associated with the same factors. These findings need to be validated in studies with a more heterogeneous sample and a greater variety of fatigability-manipulation tasks.

Cusp catastrophe model: a nonlinear model for health outcomes in nursing research.

BACKGROUND: Although health outcomes may have fundamentally nonlinear relationships with relevant behavioral, psychological, cognitively, or biological predictors, most analytical models assume a linear relationship. Furthermore, some health outcomes may have multimodal distributions, but most statistical models in common use assume a unimodal, normal distribution. Suitable nonlinear models should be developed to explain health outcomes. OBJECTIVE: The aim of this study is to provide an overview of a cusp catastrophe model for examining health outcomes and to present an example using grip strength as an indicator of a physical functioning outcome to illustrate how the technique may be used. Results using linear regression, nonlinear logistic model, and the cusp catastrophe model were compared. METHODS: Data from 935 participants from the Survey of Midlife Development in the United States (MIDUS) were analyzed. The outcome was grip strength; executive function and the inflammatory cytokine interleukin-6 were predictor variables. RESULTS: Grip strength was bimodally distributed. On the basis of fit and model selection criteria, the cusp model was superior to the linear model and the nonlinear logistic regression model. The cusp catastrophe model identified interleukin-6 as a significant asymmetry factor and executive function as a significant bifurcation factor. CONCLUSION: The cusp catastrophe model is a useful alternative for explaining the nonlinear relationships commonly seen between health outcome and its predictors. Considerations for the use of cusp catastrophe model in nursing research are discussed and recommended.

Frequency of mentally stimulating activities modifies the relationship between cardiovascular reactivity and executive function in old age.

OBJECTIVES: Recent evidence suggests that younger and middle-age adults who show greater cardiovascular reactivity (CVR) to acute mental stress demonstrate better reasoning and memory skills. The purpose of this study was to examine whether older adults would exhibit a similar positive association between CVR and executive function and whether regular engagement in mentally stimulating activities (MSA) would moderate this association. DESIGN: Secondary cross-sectional analysis. SETTING: Three clinical research centers in the Midwest and on the West Coast and East Coast. PARTICIPANTS: A total of 487 older adults participating in an ongoing national survey. MEASUREMENTS: Heart rate (HR) and low-frequency (LF) and high-frequency (HF) domains of heart rate variability (HRV) were measured at baseline and in response to standard mental stress tasks (Stroop color word task and mental arithmetic). Executive function was measured separately from the stress tasks by using five neuropsychological tests. MSA was measured by self-reported frequency of six common MSA. RESULTS: Higher HR reactivity was associated with better executive function after controlling for demographic and health characteristics and baseline HR, and the interaction between HR reactivity and MSA was significant for executive function. Higher LF-HRV reactivity was also associated with executive function, but subsequent analyses indicated that frequency of MSA was the strongest predictor of executive function in models that included LF-HRV or HF-HRV. CONCLUSIONS: Higher HR reactivity to acute psychological stress is related to better executive function in older adults. For those with lower HR reactivity, engaging frequently in MSA produced compensatory benefits for executive function.

Depressive symptoms and proinflammatory cytokines across the perinatal period in African American women.

BACKGROUND: Comparatively few studies have examined the biological mechanisms that may underlie the reported racial disparities in antenatal and postpartum depression. OBJECTIVE: To examine the associations among race, depressive symptoms and the proinflammatory cytokines interleukin (IL)-6 and tumor necrosis factor (TNF)-α across the perinatal period in a diverse sample of healthy pregnant women at elevated psychosocial risk. METHODS: 171 subjects were enrolled. Women were interviewed and blood samples drawn at 18 and 32 weeks gestation and 6 weeks and 6 months postpartum. Depressive symptoms were measured using the Edinburgh Postnatal Depression Scale. Serum levels of IL-6 and TNF-α were assayed using high sensitivity enzyme-linked immunosorbent assay kits. RESULTS: Compared with non-African American (AA) women, AA women had significantly higher levels of IL-6 (est. diff = 0.521, p = 0.02, confidence interval (CI): 0.088-0.954) but not TNF-α across all time points (est. diff = -0.060, p = 0.80, CI: -0.517 to 0.397). IL-6 was not associated with depressive symptoms but differences in IL-6 were accounted for by greater Body Mass Index in AA women. CONCLUSIONS: Compared with non-AA women, AA women entered pregnancy with elevated inflammatory cytokine levels that persisted across the perinatal period. This group difference in inflammation did not suggest increased risk for depression, but suggests other implications for long-term health.

Cusp Catastrophe Polynomial Model: Power and Sample Size Estimation.

Guastello's polynomial regression method for solving cusp catastrophe model has been widely applied to analyze nonlinear behavior outcomes. However, no statistical power analysis for this modeling approach has been reported probably due to the complex nature of the cusp catastrophe model. Since statistical power analysis is essential for research design, we propose a novel method in this paper to fill in the gap. The method is simulation-based and can be used to calculate statistical power and sample size when Guastello's polynomial regression method is used to cusp catastrophe modeling analysis. With this novel approach, a power curve is produced first to depict the relationship between statistical power and samples size under different model specifications. This power curve is then used to determine sample size required for specified statistical power. We verify the method first through four scenarios generated through Monte Carlo simulations, and followed by an application of the method with real published data in modeling early sexual initiation among young adolescents. Findings of our study suggest that this simulation-based power analysis method can be used to estimate sample size and statistical power for Guastello's polynomial regression method in cusp catastrophe modeling.

On the implication of structural zeros as independent variables in regression analysis: applications to alcohol research.

In alcohol studies, drinking outcomes such as number of days of any alcohol drinking (DAD) over a period of time do not precisely capture the differences among subjects in a study population of interest. For example, the value of 0 on DAD could mean that the subject was continually abstinent from drinking such as lifetime abstainers or the subject was alcoholic, but happened not to use any alcohol during the period of interest. In statistics, zeros of the first kind are called structural zeros, to distinguish them from the sampling zeros of the second type. As the example indicates, the structural and sampling zeros represent two groups of subjects with quite different psychosocial outcomes. In the literature on alcohol use, although many recent studies have begun to explicitly account for the differences between the two types of zeros in modeling drinking variables as a response, none has acknowledged the implications of the different types of zeros when such modeling drinking variables are used as a predictor. This paper serves as the first attempt to tackle the latter issue and illustrate the importance of disentangling the structural and sampling zeros by using simulated as well as real study data.

Disordered eating behaviors in young adult Mexican American women: prevalence and associations with health risks.

Recent research has shown that disordered eating behaviors are as prevalent in heterogenous samples of Latinas living in the U.S. as in non-Hispanic white women, yet less is known about the prevalence in women of Mexican origin. The primary purpose of this study is to report the prevalence and associations among DE behaviors and health risk of alcohol, tobacco use and obesity in a sample of N = 472 young adult college enrolled Mexican American (MA) women living in the United States. This report focuses on baseline data from a 12-month repeated measures longitudinal study. Ecological momentary assessment (EMA) was used to capture the prevalence of disordered eating and health risk behaviors in the context of everyday activities. Disordered eating behaviors including purging, binge eating, fasting and exercise were reported by approximately 15% of the sample. Food/calorie restricting, was the most prevalent behavior reported by 48% of the sample and along with binge eating was a positive predictor of BMI. Fasting was the only disordered eating behavior associated with tobacco use. These findings suggest that subclinical levels of DE behaviors are prevalent in a community sample of women of Mexican origin and are associated with health risks of tobacco use and higher BMI. Early identification of DE behaviors and community-based interventions targeting MA women may help reduce disparities associated with overweight and obesity in this population.

Weighted least-squares method for right-censored data in accelerated failure time model.

The classical accelerated failure time (AFT) model has been extensively investigated due to its direct interpretation of the covariate effects on the mean survival time in survival analysis. However, this classical AFT model and its associated methodologies are built on the fundamental assumption of data homoscedasticity. Consequently, when the homoscedasticity assumption is violated as often seen in the real applications, the estimators lose efficiency and the associated inference is not reliable. Furthermore, none of the existing methods can estimate the intercept consistently. To overcome these drawbacks, we propose a semiparametric approach in this article for both homoscedastic and heteroscedastic data. This approach utilizes a weighted least-squares equation with synthetic observations weighted by square root of their variances where the variances are estimated via the local polynomial regression. We establish the limiting distributions of the resulting coefficient estimators and prove that both slope parameters and the intercept can be consistently estimated. We evaluate the finite sample performance of the proposed approach through simulation studies and demonstrate its superiority through real example on its efficiency and reliability over the existing methods when the data is heteroscedastic.

A randomized clinical trial of an identity intervention programme for women with eating disorders.

OBJECTIVE: Findings of a randomized trial of an identity intervention programme (IIP) designed to build new positive self-schemas that are separate from other conceptions of the self in memory as the means to promote improved health in women diagnosed with eating disorders are reported. METHOD: After baseline data collection, women with anorexia nervosa or bulimia nervosa were randomly assigned to IIP (n = 34) or supportive psychotherapy (SPI) (n = 35) and followed at 1, 6, and 12 months post-intervention. RESULTS: The IIP and supportive psychotherapy were equally effective in reducing eating disorder symptoms at 1 month post-intervention, and changes were stable through the 12-month follow-up period. The IIP tended to be more effective in fostering development of positive self-schemas, and the increase was stable over time. Regardless of baseline level, an increase in the number of positive self-schemas between pre-intervention and 1-month post-intervention predicted a decrease in desire for thinness and an increase in psychological well-being and functional health over the same period. DISCUSSION: A cognitive behavioural intervention that focuses on increasing the number of positive self-schemas may be central to improving emotional health in women with anorexia nervosa and bulimia nervosa.

Trajectories of combined laboratory- and real world-based speed of processing in community-dwelling older adults.

OBJECTIVES: To characterize the trajectories of laboratory- and real world-based speed of processing (SOP) over 5 years using finite latent growth mixture modeling, and to explore associated baseline individual-level predictors and functional outcomes in 2,802 community-dwelling older adults from the Advanced Cognitive Training for Independent and Vital Elderly cohort. METHOD: Laboratory- and real world-based SOP and functional outcomes were assessed over 5 years, and candidate individual-level predictors were collected at baseline. RESULTS: After controlling for intervention assignment and demographic information, 4 distinct trajectories were identified: 4.6% of older adults had poor laboratory-based SOP and very poor real world-based SOP that both declined substantially over time; 17.9% had poor laboratory- and real world-based SOP that declined moderately; 38.7% had neutral laboratory- and real world-based SOP that maintained stable; and 37.9% had good laboratory- and real world-based SOP that declined slightly. Non-White, depression, subjective memory complaints, and vascular factors predicted the trajectories. The trajectories significantly differed in the rate of decline in basic activities of daily living, instrumental activities of daily living, and grip strength over time. DISCUSSION: Heterogeneous trajectories of SOP exist in old age. Future interventions addressing SOP should target the vulnerable group with poor SOP over time.

Effect of leisure activities on inflammation and cognitive function in an aging sample.

Cardiovascular disease risk factors (CVDRFs) increase the risk of dementia. The purpose of this study was to examine whether leisure activities (mental, physical, and social activities) modified the effect of CVDRFs on inflammatory markers and cognitive function in middle and old age. A secondary-data analysis study was conducted using data from 405 middle-age participants (40-59 years) and 342 old-age participants (60-84 years) who participated in the Survey of Midlife Development in the United States (MIDUS). CVDRFs were obtained from a combination of self-report medical history and blood-based biomarkers. Three CVDRF groups (≤1, 2, and ≥3 CVDRFs) were identified. More CVDRFs were significantly associated with higher levels of inflammatory markers in both age groups, and associated with lower levels of executive function (EF) in the old age group. CVDRFs were not related to the frequency of leisure activities in either age group. After controlling for covariates, higher levels of physical activities were significantly associated with lower levels of inflammatory markers, and higher levels of mental activities were associated with higher levels of cognitive function. In the old age group, physical activities also moderated the effect of CVDRFs on episodic memory (EM), and mental activities moderated the effect of CVDRFs on interleukin-6 (IL-6). Multiple CVDRFs may be associated with poorer cognitive function and higher inflammatory markers, but middle-age and older adults with CVDRFs may not engage in frequent physical and cognitive activities that may be protective. It is important to develop strategies to facilitate engagement in these activities from midlife.