February 22, 2012
Technological advances such as smart phones have facilitated the collection of intensive longitudinal data (ILD) in prevention science research. In a new article titled "Using the Time-Varying Effects Model (TVEM) to Examine Dynamic Associations Between Negative Affect and Self Confidence on Smoking Urges: Differences Between Successful Quitters and Relapsers" appearing in the journal Prevention Science, the authors demonstrate the advantage of applying TVEM to ILD. TVEM is a flexible approach to exploring the effects of covariates on a longitudinal outcome, where the effects are allowed to vary with time. For example, a person's mood might impact his/her urge to smoke immediately after quitting, whereas that impact may lessen with time during a successful quit attempt.
This study examined 247 people in a smoking-cessation program, 207 of whom successfully quit for two weeks and 40 of whom relapsed within the same time period. Many times a day, study participants recorded data on their mood, self-efficacy (belief in their ability to quit), and urge to smoke. Relationships were examined between the three covariates for successful quitters and relapsers. Data analysis was performed using the TVEM SAS macro that was developed by Methodology Center researchers for the estimation of coefficients in a TVEM. (SAS syntax appears in the article, and researchers can download the macro for free.) The effects of mood and self-efficacy on smoking urges changed over the course of the two weeks and differed between successful quitters and relapsers. The analysis suggests possible indications for early intervention. For example, early intervention may be warranted if a quitter’s urge to smoke fails to decrease over time. Other prevention researchers with access to ILD can use these new and accessible methods to answer new scientific questions about time-varying effects.
Shiyko, M. P., Lanza, S. T., Tan, X., Li, R., & Shiffman, S. (2012). Using the time-varying effect model (TVEM) to examine dynamic associations between negative affect and self confidence on smoking urges: Differences between successful quitters and relapsers. Prevention Science. Advance online publication. doi: 10.1007/s11121-011-0264-z