Date of Award

2015

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Psychology

Department

Psychology

First Advisor

Joseph S. Rossi

Abstract

Unhealthy lifestyle behaviors have been shown to significantly increase the risk of chronic illness. Interventions changing multiple health behaviors simultaneously show promise in reducing mortality, even more than interventions focusing on individual health behaviors. Multiple health behavior change is a new field with many fundamental questions unanswered, among them how to simultaneously measure progress in multiple health-related behaviors. Previous studies have examined several potential multivariate measurement methods but none have shown consistently superior results. Furthermore various methods may best be suited to specific behaviors, study goals, or intervention contexts. This study proposed to compare several of the most commonly used measurement methods within the context of a study examining how overall baseline severity is related to a person's ability to make positive health-related changes. This study consisted of a secondary data analysis from three randomized controlled trials for primary cancer prevention in the general population. Participants were proactively recruited based upon at risk behavior for cigarette smoking, sun exposure, or unhealthy dietary fat intake. Behaviors were examined in pairs. Participants were randomly assigned to either a treatment group which received an intervention based upon the transtheoretical model for all at risk behaviors or a control condition receiving only health behavior assessment. Health behavior change methods studied included summative indices, z-scores, standardized residuals, and progress through the stages of change. Several methods were examined to determine which method best describes the relationship between baseline severity and post-intervention outcomes. Results indicate that participants with healthier baseline behavior profiles demonstrated better post-intervention outcomes. Demographic characteristics showed comparatively smaller effects. Methods which allowed for greater detail, such as z-scores and movement through the stages of change showed greater sensitivity as evidenced by larger effect sizes. Summative indices and standardized residuals showed statistically significant results with smaller overall effects. Interventions may wish to consider tailoring based upon participant's baseline behaviors. Future studies may wish to expand the generalizability of these methods with more diverse populations, different combinations of behaviors, and/or a different set of predictor variables.

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