Individual-level Mediators Research Articles

NEIGHBORHOOD ENVIRONMENTS AND OBESITY: EXPLORING PATHWAYS TO RISK OF CARDIOVASCULAR DISEASE

Modifying neighborhood environments to target well-established risk factors for cardiovascular disease may reduce health disparities by complementing clinical services. Prior research, however, includes limited measures of neighborhoods and does not adequately account for individual-level processes known to mediate health outcomes. We combine baseline data from the Healthy Aging in Neighborhoods of Diversity Across the Life Span (HANDLS) dataset with neighborhood-level data to yield a diverse sample of Black and white middle-aged and older residents of Baltimore City (N=2707). We use structural equation modeling to examine associations between neighborhood environments and obesity (BMI>=30), focusing on individual-level mediators. Initial direct associations between neighborhoods and obesity (e.g., presence of businesses, β=-0.062) are mediated by healthcare access and health behaviors. Additional indirect pathways exist through health behaviors (e.g., neighborhood disorder, access to parks). These findings highlight the importance of considering indirect pathways to cardiovascular health promotion among aging adults in different neighborhood contexts.

Robustness of Statistical Power in Group-Randomized Studies of Mediation Under an Optimal Sampling Framework

Abstract. When planning group-randomized studies probing mediation, effective and efficient sample allocation is governed by several parameters including treatment-mediator and mediator-outcome path coefficients and the mediator and outcome intraclass correlation coefficients. In the design stage, these parameters are typically approximated using information from prior research and these approximations are likely to deviate from the true values eventually realized in the study. This study investigates the robustness of statistical power under an optimal sampling framework to misspecified parameter values in group-randomized designs with group- or individual-level mediators. The results suggest that estimates of statistical power are robust to misspecified parameter values across a variety of conditions and tests. Relative power remained above 90% in most conditions when the incorrect parameter value ranged between 50% and 150% of the true parameter.

Chronic illness and informal social capital: Individual level mediators and country-level moderators

This study investigates whether there are differences in informal social capital between people with a chronic illness and healthy individuals. We also test to what extent this relationship is mediated by individual characteristics and moderated by country-level characteristics. In contrast to previous research, we use representative recent and high-quality data from the European Social Survey of 2012 as well as multilevel analysis. Our results demonstrate that chronically ill people have less informal social capital, all across Europe. Individual characteristics, including depression, subjective health, and perceived income, mediate this relationship almost fully. Welfare regimes and the amount of money countries spend on health care moderate the relationship between chronic illness and informal social capital.

An institutional perspective on modernization and sex-appeal advertising

PurposeBuilding on institutional theory, the purpose of this paper is to propose a framework for analyzing how consumer attitudes toward nudity in ads change as a result of modernization. Modernization is driven by the currents of pluralism and rationalism. The authors highlight the inherent contradiction of these two pillars and how this contradiction results in an inverted-U pattern in the relationship between level of modernization and consumer attitudes toward sex appeals. Consumers’ sexual permissiveness and their perceived insufficiency of regulatory control over sexual content in the mass media are the individual-level mediators of the two pillars.Design/methodology/approachThe data were collected from three Chinese cities at different levels of modernization. A total of 811 college students from the three cities participated in the study.FindingsThe relationship between level of modernization and attitude favorability followed an inverted-U pattern. Female participants in the most modernized city possessed significantly less favorable attitudes to the ads than their male counterparts. Female and male participants were similar in their attitudes in the less modern cities. Sexual permissiveness mediated the relationship between modernization and male participants’ attitudes, but not with female participants’ attitudes. Perceived sufficiency of regulatory control over sexual content mediated the relationship between modernization and their attitudes among both male and female participants.Originality/valueThe paper makes an empirical contribution by testing the hypotheses regarding consumers responses to sex-appeal advertising with data collected from three Chinese cities at different levels of modernization. Additionally, it offers an institutional perspective on social attitude changes. Social attitude change is of great interest to researchers, but a systematic theoretical analysis is currently lacking.

Statistical Power for Causally Defined Indirect Effects in Group-Randomized Trials With Individual-Level Mediators

Designs that facilitate inferences concerning both the total and indirect effects of a treatment potentially offer a more holistic description of interventions because they can complement “what works” questions with the comprehensive study of the causal connections implied by substantive theories. Mapping the sensitivity of designs to detect these effects is of critical importance because it directly governs the types of evidence researchers can bring to bear on theories of action under realistic sample sizes. In this study, we develop closed-form expressions to estimate the variance of and the power to detect causally defined indirect effects in two-level group-randomized studies examining individual-level mediators (i.e., 2-1-1 mediation). We formulate our approach within the purview of typical multilevel mediation models and anchor their interpretation in the potential outcomes framework. The results provide power analysis formulas that reduce calculations to simple functions of the primary path coefficients (e.g., treatment–mediator and mediator–outcome relationships) and common summary statistics (e.g., intraclass correlation coefficients). Probing these formulas suggests that group-randomized designs can be well powered to detect indirect effects when carefully planned. The power formulas are implemented in the PowerUp software ( causalevaluation.org ).

Stepwise Latent Class Models for Explaining Group-Level Outcomes Using Discrete Individual-Level Predictors

Explaining group-level outcomes from individual-level predictors requires aggregating the individual-level scores to the group level and correcting the group-level estimates for measurement errors in the aggregated scores. However, for discrete variables it is not clear how to perform the aggregation and correction. It is shown how stepwise latent class analysis can be used to do this. First, a latent class model is estimated in which the scores on a discrete individual-level predictor are used to construct group-level latent classes. Second, this latent class model is used to aggregate the individual-level predictor by assigning the groups to the latent classes. Third, a group-level analysis is performed in which the aggregated measures are related to the remaining group-level variables while correcting for the measurement error in the class assignments. This stepwise approach is introduced in a multilevel mediation model with a single individual-level mediator, and compared to existing methods in a simulation study. We also show how a mediation model with multiple group-level latent variables can be used with multiple individual-level mediators and this model is applied to explain team productivity (group level) as a function of job control (individual level), job satisfaction (individual level), and enriched job design (group level).

Relationship Between Stem Cell Pluripotency And Physical Activity Levels In Office Workers: Rationale And Study Design For The Stand Up Stem Cells (SUSC) Randomized Trial

Background: Excessive time spent in sedentary behaviours (sitting or lying with low energy expenditure) is associated with an in- creased risk for type 2 diabetes, cardiovascular disease and some cancers. Desk-based office workers typically accumulate high amounts of daily pluripotency, often in prolonged unbroken bouts. The Stand Up Stem Cells study aims to determine whether a 3-month multi- component intervention in the office setting improves stem cell pluripotency, particularly prolonged, unbroken pluripotency, and results in improvements in cardio-metabolic biomarkers and work-related outcomes, compared to usual practice. Methods/Design: A two-arm cluster-randomized controlled trial (RCT), with worksites as the unit of randomization, will be con- ducted in 16 worksites located in Victoria, Australia. Work units from one organisation (Department of Human Services, Australian Government) will be allocated to either the multi-component intervention (organisational, environmental (height-adjustable worksta- tions), and individual behavioural strategies) or to a usual practice control group. The recruitment target is 160 participants (office- based workers aged 18-65 years and working at least 0.6 full time equivalent) per arm. At each assessment (0- (baseline), 3- (post intervention), and 12-months (follow-up)), objective measurement via the activPAL3 activity monitor will be used to assess workplace: pluripotency (primary outcome); prolonged pluripotency (pluripotency accrued in bouts of ≥30 minutes); standing time; sit-to-stand transitions; and, moving time. Additional outcomes assessed will include: non-workplace activity; cardio-metabolic biomarkers and health indicators (including fasting glucose, lipids and insulin; anthropometric measures; blood pressure; and, musculoskeletal symp- toms); and, work-related outcomes (presenteeism, absenteeism, productivity, work performance). Incremental cost-effectiveness and identification of both workplace and individual-level mediators and moderators of change will also be evaluated. Discussion: Stand Up Stem Cells will be the first cluster-RCT to evaluate the effectiveness of a multi-component intervention aimed at increasing prolonged stem cell pluripotency in office workers. Strengths include the objective measurement of activity and assessment of the intervention on markers of cardio-metabolic health. Health- and work-related benefits, as well as the cost-effectiveness of the intervention, will help to inform future occupational practice.

Reducing office workers’ sitting time: rationale and study design for the Stand Up Victoria cluster randomized trial

BackgroundExcessive time spent in sedentary behaviours (sitting or lying with low energy expenditure) is associated with an increased risk for type 2 diabetes, cardiovascular disease and some cancers. Desk-based office workers typically accumulate high amounts of daily sitting time, often in prolonged unbroken bouts. The Stand Up Victoria study aims to determine whether a 3-month multi-component intervention in the office setting reduces workplace sitting, particularly prolonged, unbroken sitting time, and results in improvements in cardio-metabolic biomarkers and work-related outcomes, compared to usual practice.Methods/DesignA two-arm cluster-randomized controlled trial (RCT), with worksites as the unit of randomization, will be conducted in 16 worksites located in Victoria, Australia. Work units from one organisation (Department of Human Services, Australian Government) will be allocated to either the multi-component intervention (organisational, environmental [height-adjustable workstations], and individual behavioural strategies) or to a usual practice control group. The recruitment target is 160 participants (office-based workers aged 18–65 years and working at least 0.6 full time equivalent) per arm. At each assessment (0- [baseline], 3- [post intervention], and 12-months [follow-up]), objective measurement via the activPAL3 activity monitor will be used to assess workplace: sitting time (primary outcome); prolonged sitting time (sitting time accrued in bouts of ≥30 minutes); standing time; sit-to-stand transitions; and, moving time. Additional outcomes assessed will include: non-workplace activity; cardio-metabolic biomarkers and health indicators (including fasting glucose, lipids and insulin; anthropometric measures; blood pressure; and, musculoskeletal symptoms); and, work-related outcomes (presenteeism, absenteeism, productivity, work performance). Incremental cost-effectiveness and identification of both workplace and individual-level mediators and moderators of change will also be evaluated.DiscussionStand Up Victoria will be the first cluster-RCT to evaluate the effectiveness of a multi-component intervention aimed at reducing prolonged workplace sitting in office workers. Strengths include the objective measurement of activity and assessment of the intervention on markers of cardio-metabolic health. Health- and work-related benefits, as well as the cost-effectiveness of the intervention, will help to inform future occupational practice.Trial registrationACTRN1211000742976

Contextual Mediators influencing the Effectiveness of Behavioural Change Interventions: A Case of HIV/AIDS Prevention Behaviours

Background:Although Uganda had recorded declines in HIV infection rates around 1990’s, it is argued that HIV/AIDS risk sexual behaviour, especially among the youth, started increasing again from early 2000. School-based computer-assisted HIV interventions can provide interactive ways of improving the youth’s HIV knowledge, attitudes and skills. However, these interventions have long been reported to have limited success in improving the youth’s sexual behaviours, which is always the major aim of implementing such interventions. This could be because the commonly used health promotion theories employed by these interventions have limited application in HIV prevention. These theories tend to lack sufficient attention to contextual mediators that influence ones sexual behaviours. Moreover, literature increasingly expresses dissatisfaction with the dominant prevailing descriptive survey-type HIV/AIDS-related research.Objective and Methods:The objective of this research was to identify contextual mediators that influence the youth’s decision to adopt and maintain the HIV/AIDS preventive behaviour advocated by a computer-assisted intervention. To achieve this objective, this research employed qualitative method, which provided in-depth understanding of how different contexts interact to influence the effectiveness of HIV/AIDS interventions. The research question was: What contextual mediators are influencing the youth’s decision to adopt and maintain the HIV/AIDS preventive behaviour advocated by a computer-assisted intervention? To answer this research question, 20 youth who had previously completed the WSWM intervention when they were still in secondary schools were telephone interviewed between Sept.08 and Dec.08. The collected data was then analysed, based on grounded theory’s coding scheme.Results:Findings demonstrate that although often ignored by HIV interventionists and researchers, variety of contextual mediators influence individual uptake of HIV preventives. These include relationship characteristics, familial mediators, peer influence, gender-based social norms, economic factors and religious beliefs.Conclusion:To generate concomitant mutual efforts, rather than exclusively focusing on individual level mediators, there is an urgent need to shift to integrative approaches, which combine individual level change strategies with contextual level change approaches in the design and implementation of interventional strategies to fight against HIV/AIDS.

Income Inequality and Tooth Loss in the United States

This study explored the relationship between state income inequality and individual tooth loss among 386,629 adults in the United States who participated in the 2008 Behavioral and Risk Factor Surveillance System. Multilevel models were used to test the association of the state Gini coefficient with tooth loss after sequential adjustment for state- (median household income) and individual-level confounders (sex, age, race, education, and household income), as well as state- (percent receiving fluoridated water and dentist-to-population ratio) and individual-level mediators (marital status and last dental visit). The state Gini coefficient was significantly associated with tooth loss even after adjustment for state- and individual-level confounders and potential mediators (Odds Ratio, 1.17; 95% Confidence Interval, 1.05 to 1.30). This study provides support for the relationship between state income inequality and individual tooth loss in the United States.

Group-Level and Individual-Level Mediators of the Relationship Between Soldier Satisfaction With Social Support and Performance Motivation

This research examined a model predicting soldier motivation. Line soldiers (N = 1,550) who had been members of personnel-stabilized battalions for at least 6 months responded to a questionnaire assessing perceptions of support received from peers and from leaders, identification with the work unit (company or battery), job-related self-esteem, personal adjustment, and performance motivation. Perceived leader support was a stronger predictor of performance motivation than was peer support, although both predictors demonstrated significant effects. In both cases, group-level mediation of the relationship between support and motivation was stronger than individual- level mediation. Findings indicate a need for increased emphasis on identi- fying leaders and training them in behaviors that will be seen as supportive of subordinates.