Exploring discontinuity in prediction of smoking cessation within the precontemplation stage of change

Construct and Predictive Validity of Three Measures of Intention to Quit Smoking: Findings From the International Tobacco Control (ITC) Netherlands Survey

Introduction

The aim of the study was to compare the construct validity and the predictive validity of three instruments to measure intention to quit smoking: a Stages of Change measure, the Motivation To Stop Scale (MTSS), and a Likert scale. We used the Theory of Planned Behavior as theoretical framework.

Methods

We used data from the International Tobacco Control Netherlands Survey. We included smokers who participated in three consecutive survey waves (n = 980). We measured attitude, subjective norm, and perceived behavioral control in 2012, intention to quit with three instruments in 2013, and having made a quit attempt in the last year in 2014. We conducted Structural Equation Modeling with three models for the instruments of intention separately and with one model that included the three instruments simultaneously.

Results

All three instruments of intention were significantly and positively related to attitude and perceived behavioral control but none was related to subjective norm. All three instruments were significantly and positively related to making a quit attempt. The relation of the Likert scale with making a quit attempt (β = 0.38) was somewhat stronger than that of the Stages of Change measure (β = 0.35) and the MTSS (β = 0.22). When entering the three instruments together into one model, only the Likert scale was significantly related to making a quit attempt.

Conclusions

All three instruments showed reasonable construct validity and comparable predictive validity. Under the studied conditions, the Likert scale performed slightly better than the Stages of Change measure and the MTSS.

Implications

An assessment of the Stages of Change, the Motivation To Stop Scale, and a Likert scale showed comparable predictive and construct validity as measures for intention to quit smoking. All three instruments can be used in future research; however, under the studied theoretical framework, that is, the Theory of Planned Behavior, the Likert scale performed slightly better than the other two instruments.

The influence of having a quit date on prediction of smoking cessation outcome

The aim of this study was to explore whether factors predicting making a quit attempt are uniform within the preparation stage of the transtheoretical model (TTM). Participants were 283 smokers, all planning to quit in the next 30 days (preparation stage), who used a computer-generated tailored advice programme. Evidence of differences in prediction of making a quit attempt was found between smokers with and without a quit date, with the predictive power of a multivariate model markedly higher among those with a set date. In particular, one aspect of pros of smoking (smoking helps you feel better when things are bad) was predictive of progression among those with a quit date, but not among those without. The results suggest that factors predicting stage progression are not uniform within the preparation stage. The results complement other recent research that has questioned the stage definitions used in the TTM and provide evidence in support of an alternative stage boundary defined by the commitment of setting a quit date.