Sweetened drink and snacking cues in adolescents: a study using ecological momentary assessment

The objective of this study was to identify physical, social, and intrapersonal cues that were associated with the consumption of sweetened beverages and sweet and salty snacks among adolescents from lower SES neighborhoods. Students were recruited from high schools with a minimum level of 25% free or reduced cost lunches. Using ecological momentary assessment, participants (N=158) were trained to answer brief questionnaires on handheld PDA devices: (a) each time they ate or drank, (b) when prompted randomly, and (c) once each evening. Data were collected over 7days for each participant. Participants reported their location (e.g., school grounds, home), mood, social environment, activities (e.g., watching TV, texting), cravings, food cues (e.g., saw a snack), and food choices. Results showed that having unhealthy snacks or sweet drinks among adolescents was associated with being at school, being with friends, feeling lonely or bored, craving a drink or snack, and being exposed to food cues. Surprisingly, sweet drink consumption was associated with exercising. Watching TV was associated with consuming sweet snacks but not with salty snacks or sweet drinks. These findings identify important environmental and intrapersonal cues to poor snacking choices that may be applied to interventions designed to disrupt these food-related, cue-behavior linked habits.

A Monte Carlo Comparison Study of the Power of the Analysis of Covariance, Simple Difference, and Residual Change Scores in Testing Two-Wave Data

This study compares the analysis of covariance (ANCOVA), difference score, and residual change score methods in testing the group effect for pretest–posttest data in terms of statistical power and Type I error rates using a Monte Carlo simulation. Previous research has mathematically shown the effect of stability of individual scores from pretest to posttest, reliability, and nonrandomization (i.e., pretest imbalance) on the performance of the ANCOVA, difference score, and residual change score methods. However, related power issues have not been adequately addressed. The authors examined the impact of stability of measurement over time, reliability of covariate and criterion, nonrandomization, sample size, and treatment effect size on statistical power of the three methods. Across conditions, ANCOVA and residual change score methods had similar power rates. When reliability was less than perfect, ANCOVA had more power than the difference score method when there was an increase from pretest to posttest and a positive baseline imbalance (i.e., treatment group had higher pretest scores than the control group), or when there was a decrease from pretest to posttest and a negative baseline imbalance, and vice versa. In case of perfect reliability, the statistical power of ANCOVA did not differ from the difference score method. For the difference score method, when reliability was low, there was no effect of stability on power, whereas when reliability was high or perfect, power increased as stability increased for medium and large effect sizes. Difference scores may be preferred over ANCOVA under certain circumstances.

Four applications of permutation methods to testing a single-mediator model

Four applications of permutation tests to the single-mediator model are described and evaluated in this study. Permutation tests work by rearranging data in many possible ways in order to estimate the sampling distribution for the test statistic. The four applications to mediation evaluated here are the permutation test of ab, the permutation joint significance test, and the noniterative and iterative permutation confidence intervals for ab. A Monte Carlo simulation study was used to compare these four tests with the four best available tests for mediation found in previous research: the joint significance test, the distribution of the product test, and the percentile and bias-corrected bootstrap tests. We compared the different methods on Type I error, power, and confidence interval coverage. The noniterative permutation confidence interval for ab was the best performer among the new methods. It successfully controlled Type I error, had power nearly as good as the most powerful existing methods, and had better coverage than any existing method. The iterative permutation confidence interval for ab had lower power than do some existing methods, but it performed better than any other method in terms of coverage. The permutation confidence interval methods are recommended when estimating a confidence interval is a primary concern. SPSS and SAS macros that estimate these confidence intervals are provided.

Mechanisms of motivational interviewing in health promotion: a Bayesian mediation analysis

BACKGROUND

Counselor behaviors that mediate the efficacy of motivational interviewing (MI) are not well understood, especially when applied to health behavior promotion. We hypothesized that client change talk mediates the relationship between counselor variables and subsequent client behavior change.

METHODS

Purposeful sampling identified individuals from a prospective randomized worksite trial using an MI intervention to promote firefighters' healthy diet and regular exercise that increased dietary intake of fruits and vegetables (n = 21) or did not increase intake of fruits and vegetables (n = 22). MI interactions were coded using the Motivational Interviewing Skill Code (MISC 2.1) to categorize counselor and firefighter verbal utterances. Both Bayesian and frequentist mediation analyses were used to investigate whether client change talk mediated the relationship between counselor skills and behavior change.

RESULTS

Counselors' global spirit, empathy, and direction and MI-consistent behavioral counts (e.g., reflections, open questions, affirmations, emphasize control) significantly correlated with firefighters' total client change talk utterances (rs = 0.42, 0.40, 0.30, and 0.61, respectively), which correlated significantly with their fruit and vegetable intake increase (r = 0.33). Both Bayesian and frequentist mediation analyses demonstrated that findings were consistent with hypotheses, such that total client change talk mediated the relationship between counselor's skills--MI-consistent behaviors [Bayesian mediated effect: αβ = .06 (.03), 95% CI = .02, .12] and MI spirit [Bayesian mediated effect: αβ = .06 (.03), 95% CI = .01, .13]--and increased fruit and vegetable consumption.

CONCLUSION

Motivational interviewing is a resource- and time-intensive intervention, and is currently being applied in many arenas. Previous research has identified the importance of counselor behaviors and client change talk in the treatment of substance use disorders. Our results indicate that similar mechanisms may underlie the effects of MI for dietary change. These results inform MI training and application by identifying those processes critical for MI success in health promotion domains.

Mechanisms in psychosocial interventions for adults living with cancer: opportunity for integration of theory, research, and practice

OBJECTIVE

The diagnosis and treatment of cancer are highly stressful experiences that can profoundly affect emotional and physical well-being. Hundreds of longitudinal investigations that identify risk and protective factors for psychological and physical adjustment in adults living with cancer and numerous randomized controlled psychosocial intervention trials constitute the relevant knowledge base on factors that promote quality of life and health in this group. A critical step for the development of maximally effective interventions is to attend to the mechanisms by which interventions achieve their effects. Our goals in this article are to provide a rationale for theoretical and empirical consideration of mediating processes in intervention research, review existing randomized psychosocial intervention trials for adults diagnosed with cancer that include evaluation of mediators, and offer recommendations for research.

METHOD

We draw from the existing conceptual and empirical literature regarding examination of mediating processes and review 16 randomized controlled trials that include evaluations of mediators.

RESULTS

The current conceptual and empirical literature on evaluating mediators of interventions provides robust rationales and procedures for testing mediators of psychosocial interventions for adults diagnosed with cancer. Promising classes of mediators include alterations in cognitions (i.e., expectancies, illness representations), self-efficacy for using coping strategies and other skills targeted by the intervention, psychological and physical symptoms related to cancer (e.g., mood disturbance, pain), and psychosocial resources (e.g., self-esteem).

CONCLUSIONS

Focused attention to mechanisms underlying the efficacy of interventions can help integrate theory, research, and practice to promote the well-being and health of individuals with cancer.

A Qualitative Mediation Study to Evaluate a School-Based Tobacco Prevention Program in India (Project MYTRI)

Causal mediating processes were examined using qualitative methods to evaluate a tobacco-use prevention program for adolescents in India, Project MYTRI (Mobilizing Youth for Tobacco-Related Initiatives in India). Interviews were conducted with Project MYTRI leaders and staff persons. The focus of the interviews was to learn about the program implementation and to characterize how Project MYTRI classroom sessions altered student-level psychosocial risk factors (mediators) to prevent or reduce tobacco use among students in intervention schools in Delhi and Chennai. From qualitative analysis, key mediating variables were identified (students' tobacco knowledge, skills development, beliefs about tobacco, intentional beliefs, advocacy beliefs, and self-efficacy beliefs), a qualitative mediation path model was drawn, causal processes were described, and contextual influences (potential moderators) were explained. The qualitative findings complemented the results of statistical mediation analysis, yielding a detailed and contextualized description of how Project MYTRI affected students.

Do cognitive attributions for smoking predict subsequent smoking development?

To develop more effective anti-smoking programs, it is important to understand the factors that influence people to smoke. Guided by attribution theory, a longitudinal study was conducted to investigate how individuals' cognitive attributions for smoking were associated with subsequent smoking development and through which pathways. Middle and high school students in seven large cities in China (N=12,382; 48.5% boys and 51.5% girls) completed two annual surveys. Associations between cognitive attributions for smoking and subsequent smoking initiation and progression were tested with multilevel analysis, taking into account plausible moderation effects of gender and baseline smoking status. Mediation effects of susceptibility to smoking were investigated using statistical mediation analysis (MacKinnon, 2008). Six out of eight tested themes of cognitive attributions were associated with subsequent smoking development. Curiosity (β=0.11, p<0.001) and autonomy (β=0.08, p=0.019) were associated with smoking initiation among baseline non-smokers. Coping (β=0.07, p<0.001) and social image (β=0.10, p=<.0001) were associated with smoking progression among baseline lifetime smokers. Social image (β=0.05, p=0.043), engagement (β=0.07, p=0.003), and mental enhancement (β=0.15, p<0.001) were associated with smoking progression among baseline past 30-day smokers. More attributions were associated with smoking development among males than among females. Susceptibility to smoking partially mediated most of the associations, with the proportion of mediated effects ranging from 4.3% to 30.8%. This study identifies the roles that cognitive attributions for smoking play in subsequent smoking development. These attributions could be addressed in smoking prevention programs.

Guidelines for the Investigation of Mediating Variables in Business Research

Business theories often specify the mediating mechanisms by which a predictor variable affects an outcome variable. In the last 30 years, investigations of mediating processes have become more widespread with corresponding developments in statistical methods to conduct these tests. The purpose of this article is to provide guidelines for mediation studies by focusing on decisions made prior to the research study that affect the clarity of conclusions from a mediation study, the statistical models for mediation analysis, and methods to improve interpretation of mediation results after the research study. Throughout this article, the importance of a program of experimental and observational research for investigating mediating mechanisms is emphasized.

Explanation of Two Anomalous Results in Statistical Mediation Analysis

Previous studies of different methods of testing mediation models have consistently found two anomalous results. The first result is elevated Type I error rates for the bias-corrected and accelerated bias-corrected bootstrap tests not found in nonresampling tests or in resampling tests that did not include a bias correction. This is of special concern as the bias-corrected bootstrap is often recommended and used due to its higher statistical power compared with other tests. The second result is statistical power reaching an asymptote far below 1.0 and in some conditions even declining slightly as the size of the relationship between X and M, a, increased. Two computer simulations were conducted to examine these findings in greater detail. Results from the first simulation found that the increased Type I error rates for the bias-corrected and accelerated bias-corrected bootstrap are a function of an interaction between the size of the individual paths making up the mediated effect and the sample size, such that elevated Type I error rates occur when the sample size is small and the effect size of the nonzero path is medium or larger. Results from the second simulation found that stagnation and decreases in statistical power as a function of the effect size of the a path occurred primarily when the path between M and Y, b, was small. Two empirical mediation examples are provided using data from a steroid prevention and health promotion program aimed at high school football players (Athletes Training and Learning to Avoid Steroids; Goldberg et al., 1996), one to illustrate a possible Type I error for the bias-corrected bootstrap test and a second to illustrate a loss in power related to the size of a. Implications of these findings are discussed.

Integrating Mediators and Moderators in Research Design

The purpose of this article is to describe mediating variables and moderating variables and provide reasons for integrating them in outcome studies. Separate sections describe examples of moderating and mediating variables and the simplest statistical model for investigating each variable. The strengths and limitations of incorporating mediating and moderating variables in a research study are discussed as well as approaches to routinely including these variables in outcome research. The routine inclusion of mediating and moderating variables holds the promise of increasing the amount of information from outcome studies by generating practical information about interventions as well as testing theory. The primary focus is on mediating and moderating variables for intervention research but many issues apply to nonintervention research as well.

The PHLAME (Promoting Healthy Lifestyles: Alternative Models' Effects) firefighter study: testing mediating mechanisms

This paper examines the mechanisms by which PHLAME (Promoting Healthy Lifestyles: Alternative Models' Effects), a health promotion intervention, improved healthy eating and exercise behavior among firefighters, a population at high risk for health problems due to occupational hazards. In a randomized trial, 397 firefighters participated in either the PHLAME team intervention with their work shift or a control condition. Intervention sessions taught benefits of a healthy diet and regular exercise, and sought to improve social norms and social support from coworkers for healthy behavior. At posttest, team intervention participants had increased their fruit and vegetable consumption as compared to control participants. An increase in knowledge of fruit and vegetable benefits and improved dietary coworker norms partially mediated these effects. Exercise habits and VO2 max were related to targeted mediators but were not significantly changed by the team intervention. Partial support was found for both the action and conceptual theories underlying the intervention. Our findings illustrate how an effective program's process can be deconstructed to understand the underpinnings of behavior change and refine interventions. Further, fire stations may improve the health of firefighters by emphasizing the benefits of healthy diet and exercise behaviors while also encouraging behavior change by coworkers as a whole.

Investigating ethnic differences in adolescent alcohol use and peer norms using semi-continuous latent growth models

AIMS

To investigate whether ethnic differences in vulnerability to peer norms supportive of alcohol use is a viable, partial explanation for the ethnic differences in reported prevalence and amount of alcohol use during high school.

METHODS

Survey data from a sample of 680 adolescents from Project STAR (Students Taught Awareness and Resistance) of the Midwestern Prevention Project were used. Hypotheses were tested using sequential, semi-continuous growth curve models.

RESULTS

Relative to Black adolescents, White adolescents reported greater peer alcohol use during middle school and were much more likely to consume alcohol during high school. General peer norms in seventh grade and middle school growth in alcohol use norms among close friends was predictive of a greater propensity to consume alcohol in ninth grade among White adolescents.

CONCLUSION

Lower peer norms for alcohol use among Black adolescents might better account for differences between Black and White adolescents than the possibility that White adolescents are more vulnerable to peer norms.

Investigating ethnic differences in adolescent alcohol use and peer norms using semi-continuous latent growth models

AIMS

To investigate whether ethnic differences in vulnerability to peer norms supportive of alcohol use is a viable, partial explanation for the ethnic differences in reported prevalence and amount of alcohol use during high school.

METHODS

Survey data from a sample of 680 adolescents from Project STAR (Students Taught Awareness and Resistance) of the Midwestern Prevention Project were used. Hypotheses were tested using sequential, semi-continuous growth curve models.

RESULTS

Relative to Black adolescents, White adolescents reported greater peer alcohol use during middle school and were much more likely to consume alcohol during high school. General peer norms in seventh grade and middle school growth in alcohol use norms among close friends was predictive of a greater propensity to consume alcohol in ninth grade among White adolescents.

CONCLUSION

Lower peer norms for alcohol use among Black adolescents might better account for differences between Black and White adolescents than the possibility that White adolescents are more vulnerable to peer norms.

Long-term impact of prevention programs to promote effective parenting: lasting effects but uncertain processes

This article reviews findings from 46 randomized experimental trials of preventive parenting interventions. The findings of these trials provide evidence of effects to prevent a wide range of problem outcomes and to promote competencies from one to 20 years later. However, there is a paucity of evidence concerning the processes that account for program effects. Three alternative pathways are proposed as a framework for future research on the long-term effects of preventive parenting programs: (a) through program effects on parenting skills, perceptions of parental efficacy, and reduction in barriers to effective parenting; (b) through program-induced reductions in short-term problems of youth that persist over time, improvements in youth adaptation to stress, and improvements in youth belief systems concerning the self and their relationships with others; and (c) through effects on contexts in which youth become involved and on youth-environment transactions.

Long-term impact of prevention programs to promote effective parenting: lasting effects but uncertain processes

This article reviews findings from 46 randomized experimental trials of preventive parenting interventions. The findings of these trials provide evidence of effects to prevent a wide range of problem outcomes and to promote competencies from one to 20 years later. However, there is a paucity of evidence concerning the processes that account for program effects. Three alternative pathways are proposed as a framework for future research on the long-term effects of preventive parenting programs: (a) through program effects on parenting skills, perceptions of parental efficacy, and reduction in barriers to effective parenting; (b) through program-induced reductions in short-term problems of youth that persist over time, improvements in youth adaptation to stress, and improvements in youth belief systems concerning the self and their relationships with others; and (c) through effects on contexts in which youth become involved and on youth-environment transactions.

Long-term impact of prevention programs to promote effective parenting: lasting effects but uncertain processes

This article reviews findings from 46 randomized experimental trials of preventive parenting interventions. The findings of these trials provide evidence of effects to prevent a wide range of problem outcomes and to promote competencies from one to 20 years later. However, there is a paucity of evidence concerning the processes that account for program effects. Three alternative pathways are proposed as a framework for future research on the long-term effects of preventive parenting programs: (a) through program effects on parenting skills, perceptions of parental efficacy, and reduction in barriers to effective parenting; (b) through program-induced reductions in short-term problems of youth that persist over time, improvements in youth adaptation to stress, and improvements in youth belief systems concerning the self and their relationships with others; and (c) through effects on contexts in which youth become involved and on youth-environment transactions.

Statistical analysis for identifying mediating variables in public health dentistry interventions

OBJECTIVE

This article provides an overview of statistical mediation analysis methods in the evaluation of public health dentistry interventions.

METHODS AND RESULTS

First, reasons for conducting mediation analysis are outlined, followed by a discussion of the link between the mediation model and theoretical bases of interventions. Second, the basic statistical procedures in mediation analysis are presented. An example application to data from a hypothetical intervention is provided in Appendix A. Third, interpretation of the results from statistical mediation analysis is described along with additional information pertinent to identifying true mediation relations.

CONCLUSIONS

Guidelines for describing mediation analyses in research articles related to public health dentistry intervention studies are outlined.

Long-term effects of a worksite health promotion program for firefighters

OBJECTIVE

To describe effects of 2 worksite health promotion programs for firefighters, both immediate outcomes and the long-term consequences for 4 years following the interventions.

METHODS

At baseline, 599 firefighters were assessed, randomized by fire station to control and 2 different intervention conditions, and reevaluated with 6 annual follow-up measurements.

RESULTS

Both a team-centered peer-taught curriculum and an individual motivational interviewing intervention demonstrated positive effects on BMI, with team effects on nutrition behavior and physical activity at one year. Most differences between intervention and control groups dissipated at later annual assessments. However, the trajectory of behaviors across time generally was positive for all groups, consistent with lasting effects and diffusion of program benefits across experimental groups within the worksites.

CONCLUSIONS

Although one-year programmatic effects did not remain over time, the long-term pattern of behaviors suggested these worksites as a whole were healthier more than 3 years following the interventions.

The IGNITE (investigation to guide new insight into translational effectiveness) trial: Protocol for a translational study of an evidenced-based wellness program in fire departments

BACKGROUND

Worksites are important locations for interventions to promote health. However, occupational programs with documented efficacy often are not used, and those being implemented have not been studied. The research in this report was funded through the American Reinvestment and Recovery Act Challenge Topic 'Pathways for Translational Research,' to define and prioritize determinants that enable and hinder translation of evidenced-based health interventions in well-defined settings.

METHODS

The IGNITE (investigation to guide new insights for translational effectiveness) trial is a prospective cohort study of a worksite wellness and injury reduction program from adoption to final outcomes among 12 fire departments. It will employ a mixed methods strategy to define a translational model. We will assess decision to adopt, installation, use, and outcomes (reach, individual outcomes, and economic effects) using onsite measurements, surveys, focus groups, and key informant interviews. Quantitative data will be used to define the model and conduct mediation analysis of each translational phase. Qualitative data will expand on, challenge, and confirm survey findings and allow a more thorough understanding and convergent validity by overcoming biases in qualitative and quantitative methods used alone.

DISCUSSION

Findings will inform worksite wellness in fire departments. The resultant prioritized influences and model of effective translation can be validated and manipulated in these and other settings to more efficiently move science to service.

Bayesian mediation analysis

In this article, we propose Bayesian analysis of mediation effects. Compared with conventional frequentist mediation analysis, the Bayesian approach has several advantages. First, it allows researchers to incorporate prior information into the mediation analysis, thus potentially improving the efficiency of estimates. Second, under the Bayesian mediation analysis, inference is straightforward and exact, which makes it appealing for studies with small samples. Third, the Bayesian approach is conceptually simpler for multilevel mediation analysis. Simulation studies and analysis of 2 data sets are used to illustrate the proposed methods. (PsycINFO Database Record (c) 2009 APA, all rights reserved).

A general model for testing mediation and moderation effects

This paper describes methods for testing mediation and moderation effects in a dataset, both together and separately. Investigations of this kind are especially valuable in prevention research to obtain information on the process by which a program achieves its effects and whether the program is effective for subgroups of individuals. A general model that simultaneously estimates mediation and moderation effects is presented, and the utility of combining the effects into a single model is described. Possible effects of interest in the model are explained, as are statistical methods to assess these effects. The methods are further illustrated in a hypothetical prevention program example.

A general model for testing mediation and moderation effects

This paper describes methods for testing mediation and moderation effects in a dataset, both together and separately. Investigations of this kind are especially valuable in prevention research to obtain information on the process by which a program achieves its effects and whether the program is effective for subgroups of individuals. A general model that simultaneously estimates mediation and moderation effects is presented, and the utility of combining the effects into a single model is described. Possible effects of interest in the model are explained, as are statistical methods to assess these effects. The methods are further illustrated in a hypothetical prevention program example.